DECONTAMINATION GEL AND METHOD FOR DECONTAMINATION OF SURFACES BY IMMERSION IN THIS GEL

Description

TECHNICAL FIELD

[0001] The present invention relates to a decontamination gel which can be used for the decontamination of surfaces.

[0002] The gel according to the invention is particularly suitable for application to contaminated surfaces of parts by soaking, immersion and for decontaminating contaminated surfaces of parts of small size and / or complex shapes.

[0003] The present invention further relates to a method for decontaminating contaminated surfaces of parts in which a gel is applied to the contaminated surfaces of the parts by soaking or immersion.

[0004] The method and the gel according to the invention allow the decontamination of all kinds of surfaces such as surfaces made of metallic, plastic, mineral materials such as vitreous materials.

[0005] The method and gel according to the invention are particularly applicable to the decontamination of surfaces of porous materials such as cementitious materials like mortars and concretes; bricks; plasters; and natural stone.

[0006] The method and the gel according to the invention also allow the elimination of all kinds of contaminants and in particular chemical, biological, or nuclear, radioactive contaminants.

[0007] The technical field of the invention can thus, in general, be defined as being that of the decontamination of surfaces with a view to eliminating pollutants, contaminants which are found on this surface and possibly under this surface, and whose presence on and under these surfaces is not desired. STATE OF THE PRIOR ART

[0008] Over the past twenty years, numerous solid material decontamination processes have been developed to meet the needs of the nuclear industry, particularly as it is in a phase of shutting down and dismantling first-generation installations.

[0009] Furthermore, the succession of terrorist acts by chemical or biological means is prompting many countries to build genuine research programs to equip themselves with effective means of decontaminating property and people.

[0010] Generally speaking, the easiest and least expensive sanitation techniques to implement consist of bringing a liquid containing a chemical reagent, which can be called a decontaminating solution, into contact with surfaces contaminated, for example by biological contamination.

[0011] The application of the decontaminating solution is generally carried out by spraying or washing, coupled or not with a mechanical effect such as brushing.

[0012] Thus, document [1] describes a cleaning composition for removing antibacterial and other agents used in decontamination following a biological attack. This composition comprises in particular ethanol, isopropanol, ethylene glycol n-hexyl ether, a bromide and a chloride.

[0013] Document [2] describes a large-scale decontamination process in which a solid, stable peracid, or a solid, stable source of a peracid, is contacted with a contaminated surface.

[0014] More recently, new wetting techniques using nebulisation or foam projection have made it possible to reduce the quantity of decontaminating product used and therefore the volume of chemical effluents produced. In this regard, reference may be made to documents [3] and [4].

[0015] Other processes use chemical reagents in gaseous form, such as the process described in document [5] which uses biocidal agents in gaseous form, such as hydrogen peroxide or ozone.

[0016] Whatever the technique used, the major risk associated with the processes described above remains the risk of dissemination of toxic agents into the environment.

[0017] Furthermore, the process, which uses biocidal agents in gaseous form, is only effective when used in closed enclosures.

[0018] To address the problem of recovering contamination, a third category of process has more recently been developed.

[0019] In these processes, the contamination is transferred to a solid support material capable of trapping contaminants by sorption, or even destroying them in the case of toxic biological species. The waste thus generated is then also found in solid form. Obtaining solid waste is particularly interesting to limit the risks of dispersion of toxic agents in the environment but also to facilitate the management and ultimate treatment of the waste produced.

[0020] Various technologies using a solid support material have already been developed.

[0021] First of all, there is the so-called "powder glove" technology intended for the decontamination of persistent toxic liquids found on the skin or on equipment.

[0022] In this glove, the decontaminating agent is an absorbent powder, usually Fuller's Earth.

[0023] The implementation of this glove is carried out in three successive stages: application of the powder to the contaminated area of ​​the substrate (skin or material) by tapping; absorption of the toxic liquid; wiping, cleaning the substrate using the sponge side of the glove [6].

[0024] In the case of contamination including pathogens, the powder glove may also contain an oxidizing agent capable of inactivating this contamination trapped by the Fuller's Earth.

[0025] This technique, particularly suited to personal care, nevertheless remains limited to the treatment of low-level liquid contamination.

[0026] Other decontamination products, which come in the form of a gel, generate solid waste and thus make it possible to avoid the use of liquid solutions to treat and sanitize rooms with large surfaces and complex geometries.

[0027] These gels are generally applied by spraying them onto the surface to be decontaminated.

[0028] After a contact time of the gel with the surface to be decontaminated, equivalent to the evaporation time of the solvent, the dry waste obtained is removed by brushing and / or suction. The major advantage of these processes is their suitability for treating large surfaces and uneven geometries.

[0029] Thus, document [7] describes a gel composition containing oxidizing agents for the chemical or biological decontamination of contaminated areas. This composition is prepared by adding thickening or gelling agents in the form of colloids to an oxidizing agent solution to form a viscous colloidal gel.

[0030] This solution can be an aqueous or organic solution.

[0031] Thickening or gelling agents may be selected from silica, alumina, aluminosilicates, mixtures of silica and alumina, and clays such as smectite.

[0032] Oxidizing agents include sodium hypochlorite, ammonium persulfate, or hydrogen peroxide.

[0033] It is stated that these gels can be used to eliminate biological agents such as microorganisms like bacteria, fungi, viruses, and spores, or chemical agents such as nerve gas.

[0034] The gels are then sprayed onto the surfaces to be treated and then recovered by suction after drying.

[0035] The gel formulations developed by the Lawrence Livermore National Laboratory under the names L-Gel 115 and L-Gel 200 are similar to the formulations developed in document [7] and are implemented using the so-called "L-Gel" process. These gels are formulated from oxidizing acid solutions to which organic solvents and a silica filler are added. The gels are then sprayed onto the surfaces to be treated and recovered by suction after drying. Among the critical points of this process, we can cite the rheological properties of the gelled product.

[0036] Indeed, in order to avoid drips, particularly when the gel is applied to walls or ceilings, it is applied in the form of very thin films with a thickness not exceeding, in document [7], 125 µm. This results in a dry powdery waste which can lead, if the treatment is not fully effective, to a dissemination of bio-toxic and chemical species, such as oxidizing compounds, into the atmosphere.

[0037] However, the performance of the process appears to be very moderate with regard to biological and nuclear contamination.

[0038] Thus the performance of the process, determined with respect to contamination by Anthrax in the form of an aerosol deposited by spraying on reference materials (10 7< and 10 8< spores per sample of 0.16 m 2< or 6000 to 63000 spores / cm 2< ), shows that it does not allow a reduction in contamination greater than 5 decades [8].

[0039] However, there is no precise assessment of the performance of this process with regard to nuclear contamination.

[0040] Furthermore, in the context of nuclear decontamination, gel formulations that overcome the problems associated with the powdery nature of dry waste and increase the effectiveness of the gel process have been the subject of documents [9] and

[10] . The gel formulations described therein allow the contamination to be released in particulate form by means of low erosion of the support material. The contaminant is then trapped in the dry gel residue [9],

[10] .

[0041] These gels have been successfully implemented on various nuclear decontamination sites. The dose rate reduction factors obtained are well over 20, even on resistant materials such as stainless steel. This type of treatment also has the advantage of meeting the safety criteria for materials with a view to their reuse.

[0042] However, the gels described in the prior art documents, such as the aspirable gels described in documents [9] and

[10] , despite all their advantages, are not compatible with the decontamination of parts of small sizes and / or complex shapes and geometries.

[0043] In fact, the decontamination of these small and / or complex shaped and geometric parts is generally carried out by a decontamination process called the soaking process or immersion process which consists of a simple immersion of the contaminated parts in a decontaminating bath.

[0044] For small volume parts, the immersion process allows both to limit the intervention time of operators, but also to ensure the presence of the decontaminating agent at every point of the part, including in the most difficult to access areas.

[0045] However, the inventors have demonstrated that the gels described in the prior art documents are not suitable for use in such a soaking process.

[0046] The baths used in these dipping processes are currently liquid solutions which present high risks of spreading or dripping when the part is removed from the bath.

[0047] There is therefore, in view of the above, a need for a decontamination gel which can be implemented satisfactorily in a decontamination process by soaking or immersion and which can thus allow the decontamination of parts of small sizes and / or shapes, of complex geometries.

[0048] In other words, there is a need for a decontamination gel which, while having all the excellent properties of the decontamination gels of the prior art and in particular of the aspirable decontamination gels described in documents [9] and

[10] , does not have the drawbacks thereof, in particular with regard to their unsuitability for use in a decontamination process by soaking or immersion.

[0049] The aim of the present invention is to provide a decontamination gel which meets this need, among other things.

[0050] The aim of the present invention can also be defined as the improvement of the gels and methods of the prior art and in particular those of documents [9] and

[10] in order to make them compatible with the decontamination of parts of small sizes and / or complex geometries by a decontamination method by soaking or immersion.

[0051] Another aim of the present invention is to provide a decontamination gel which allows the effective decontamination of porous surfaces, in particular mineral surfaces, and which ensures the decontamination, in particular biological, in depth of such surfaces to a depth which can reach, for example, several millimeters. STATEMENT OF THE INVENTION

[0052] This aim, and others, are achieved, in accordance with the invention, by a decontamination gel as defined in the attached set of claims, consisting of a colloidal solution comprising or consisting of: 0.1% to 30% by mass, preferably 0.1% to 25% by mass, more preferably 5% to 25% by mass, more preferably 8% to 20% by mass, relative to the mass of the gel, of at least one inorganic viscosifying agent; 0.01% to 5% by mass, preferably 0.05% to 3% by mass, relative to the mass of the gel, of at least one viscosity variation agent which, when subjected to at least one stimulus, preferably external to the gel, causes a variation in the viscosity of the gel, said stimulus, preferably external to the gel, being chosen from chemical stimuli such as a variation in the oxidation-reduction potential of the gel; thermal stimuli such as a variation in the temperature of the gel; physical stimuli such as exposure to an electromagnetic wave; and combinations of two or more of said stimuli; said viscosity variation agent not being a superabsorbent polymer;said viscosity variation agent being selected from the group consisting of polysaccharides, oxidizing compounds, magnetic particles and compounds whose viscosity varies when exposed to electromagnetic radiation of different wavelengths; 0.1 to 10 mol / L of gel, preferably 0.5 to 10 mol / L of gel, more preferably 1 to 10 mol / L of gel, of at least one active decontamination agent different from said viscosity variation agent; 0.1% to 2% by mass relative to the mass of the gel, of at least one surfactant and preferably at least one non-ionic surfactant; optionally 0.05% to 5% by mass, preferably 0.05% to 2% by mass relative to the mass of the gel, of at least one superabsorbent polymer; and the remainder of solvent. ;

[0053] The gel according to the invention contains a viscosity variation agent which, when subjected to at least one stimulus, preferably external to the gel, causes a variation in the viscosity of the gel, preferably an increase in the viscosity of the gel or a jump in viscosity.

[0054] Preferably, this variation in the viscosity of the gel is a variation, and in particular an increase, which can be described as rapid and significant.

[0055] This viscosity variation agent can also be called an agent generating versatile rheological behavior.

[0056] In other words, the gel according to the invention comprises one or more agents which are capable of inducing a variation, evolution, generally significant in the viscosity of the gel.

[0057] This change in viscosity must generally be sudden and is the result of an external stimulus to the gel generated in a simple way.

[0058] By rapid, sudden, significant change in the viscosity of the gel, for example rapid, sudden, significant increase, is generally meant that the viscosity of the gel undergoes a variation, preferably an increase of 0.05 Pa.s to 10 5< Pa.s in a duration of less than 5 seconds, preferably less than 2 seconds, more preferably less than or equal to 1 second, for example in a duration of between 0.5 seconds and 1 second from the moment when the gel is subjected to said stimulus.

[0059] Generally, the gel passes from a state that can be described as liquid with a viscosity of less than 0.1 Pa.s to a state that can be described as truly gelled with a viscosity greater than 100 Pa.s.

[0060] Said stimulus, preferably external to the gel, is chosen from chemical stimuli such as a variation in the oxidation-reduction potential of the gel; thermal stimuli such as a variation in the temperature of the gel; physical stimuli such as exposure to an electromagnetic wave; and combinations of two or more of said stimuli.

[0061] In the case where the stimulus is a chemical stimulus, it may be a variation in the redox potential of the gel.

[0062] For example, an oxidizing decontamination gel can be formulated whose viscosity increases suddenly upon contact with a reducer consisting, for example, of the material of the part to be decontaminated.

[0063] In the case where the stimulus is a variation of the redox potential of the gel, the viscosity variation agent is chosen from oxidizing compounds such as Ce IV ions, H 2 O 2 , KMnO 4 etc.

[0064] In the case where the stimulus is a chemical stimulus, it can also be a variation in the acidity of the gel. In this case, the viscosity variation agent can be chosen from carrageenans whose gelling mechanism is sensitive to acidity. As mentioned below, the gelling mechanism of carrageenans is also sensitive to temperature.

[0065] In the case where the stimulus is a thermal stimulus, it may be a variation in the temperature of the gel and the viscosity variation agent is then chosen from organic viscosifying agents whose viscosity varies as a function of temperature.

[0066] These organic, temperature-sensitive viscosifying agents, whose viscosity varies depending on the temperature, are chosen from polysaccharides, such as carrageenans.

[0067] Carrageenans in fact exhibit, in aqueous media, significant viscosity variations depending on the temperature, their viscosity generally decreasing significantly depending on the temperature (Example 6).

[0068] Carrageenans are gelling agents or thickeners commonly used in the food industry and derived from red algae.

[0069] The ability of these products to gel depends on the number and position of the sulfonate groups on the carbon rings ( Figures 4 A and B )

[13] .

[0070] In this paper, we are primarily interested in the forms (iota) ( Figure 4B ) and κ (kappa) ( Figure 4A ) known to form “soft” gels and “brittle” gels respectively.

[0071] The gelling mechanism of this type of product involves a change in the conformation of the carbon chains; entangled in a disordered manner at high temperature, they organize themselves into helices once the sol-gel transition point is reached ( Figure 5 )

[14] .

[0072] Thus, a gel according to the invention containing carrageenans, preferably κ-carrageenans and forms at a temperature of 30°C to 80°C, for example 40°C to 65°C, a liquid and low-viscosity bath in which the part to be decontaminated is immersed. When the part covered with a film of this gel is removed from the heated bath, the gel undergoes a sudden decrease in temperature, for example to a temperature of 15°C to 25°C, and sees its viscosity rapidly increase by passing from a liquid state to a truly gelled state.

[0073] The content of organic viscosifying agents, such as carrageenans, whose viscosity varies depending on the temperature, is generally between 0% and 5%, preferably between 0.1% and 5% by mass of gel, more preferably between 0.1% and 2% by mass of the total mass of the gel.

[0074] In these proportions, the organic nature of the viscosity variation agent is in no way detrimental to the use of the decontaminating product in a nuclear context where the risks of degradation of waste by radiolysis must necessarily be taken into account.

[0075] In the case where the stimulus is a physical stimulus, it may be the exposure or not of the gel to an electromagnetic field.

[0076] The viscosity variation agent is then chosen from magnetic particles.

[0077] Indeed, the viscosity transitions required by the method of the present invention described below can be induced by the presence of magneto-sensitive particles in the composition of the gel.

[0078] Suspensions of micrometer-sized magnetic particles exhibit a large difference in rheological behavior when the complex fluid is subjected to a magnetic field or not.

[0079] By aligning under the effect of the field, the solid agglomerates containing the magnetic particles induce a significant shear resistance, hence the evolution of their viscosity

[15] .

[0080] By choosing the direction of alignment of the particles through the magnetic field, one can either increase or, on the contrary, reduce the shear resistance, thus promoting the appearance of a liquid phase or generating gelation. This amounts to saying that the stimulus can consist either of the beginning of the exposure of the gel to a magnetic field, or of the end of the exposure of the gel to a magnetic field.

[0081] Several synthesis processes make it possible to obtain iron / silica composites in the form of particles containing a magnetic iron oxide core and exhibiting magnetorheological behavior

[16] ,

[17] .

[0082] Document

[18] describes a procedure which makes it possible to obtain ferromagnetic silica particles which can be used in the gels according to the invention ( Figure 6 ).

[0083] As an example, we can also cite the product sold by the company EVONIK ®< under the commercial designation “ MagSilica ", which is a nanostructured iron oxide in a silica matrix.

[0084] In the context of the intended application, this type of adjuvant is particularly interesting since it is directly compatible with silica which can be used as a viscosifying mineral filler in the gel according to the invention.

[0085] Still in the case where the stimulus is a physical stimulus, it can be the exposure of the gel to radiation, in the range of infrared to ultraviolet radiation, this radiation inducing a variation in the viscosity of the gel.

[0086] The viscosity variation agent is then chosen from among compounds whose viscosity varies when exposed to radiation of different wavelengths. We are therefore in the presence of a stimulus that can more precisely be described as physicochemical.

[0087] Thus, ultraviolet radiation can be used as external stimuli activating a photosensitive adjuvant. The coating gel according to the invention can then comprise an adjuvant whose rheological behavior is a function of at least two wavelengths (one for the liquid state, the other for the gelled state)

[19] .

[0088] The variation in the viscosity of the gel can also occur following the combination of several stimuli chosen from the stimuli listed above, for example the combination of several stimuli chosen from a physical stimulus, a chemical stimulus for example a variation in the oxidation-reduction potential, and a physicochemical stimulus for example exposure to UV radiation.

[0089] This combination of external stresses to move from one rheological state to another is notably described in documents

[20] and

[21] .

[0090] The gels according to the invention have never been described in the prior art.

[0091] In particular, the incorporation into a decontamination gel of a viscosity variation agent which, when subjected to at least one stimulus external to the gel, causes a variation in the viscosity of the gel, preferably a significant and rapid increase in the viscosity of the gel, and a fortiorithe combination in such a gel of such a viscosity variation agent with a decontamination agent such as a biological decontamination agent, has never been described in the prior art, as represented in particular by the documents cited above.

[0092] The incorporation of a viscosity variation agent into a decontamination gel has also never been suggested in the prior art as represented in particular by the documents cited above.

[0093] The gels according to the invention meet all of the needs mentioned above; they do not have the drawbacks, defects, limitations and disadvantages of the gels of the prior art such as those described in the documents mentioned above.

[0094] The gels according to the invention solve the problems presented by the decontamination gels of the prior art such as those described in the documents mentioned above, and in particular the gels of documents [9] and

[10] without presenting the drawbacks but while retaining all the known advantageous properties of these gels.

[0095] The formulation of the gel according to the invention, in particular due to the presence in this gel of a viscosity variation agent, surprisingly allows the use of the gel according to the invention in a decontamination process, called a decontamination process by immersion or soaking, which consists of a simple immersion of the contaminated parts in a decontaminating bath.

[0096] Therefore, the gel according to the invention can be called “coating gel”, since the part to be decontaminated is coated with a film of the gel according to the invention, by soaking, immersion in a bath.

[0097] The gels described in the prior art documents which do not contain such a viscosity variation agent are absolutely not suitable for use in a decontamination process by immersion or soaking. The use of a gel in such a process is made possible for the first time thanks to the specific composition of the gel according to the invention, and this is one of the essential problems of the gels of the prior art which is therefore overcome by the gel according to the invention.

[0098] The gel according to the invention replaces the liquid solutions which are usually used for dipping baths and does not have the drawbacks thereof, in particular with regard to the drips observed with these liquid dipping baths when the part, which has been immersed in the liquid dipping bath, and which is therefore coated with the liquid solution, is removed from it.

[0099] The gel that forms the bath in which the part to be decontaminated is immersed has a low viscosity and is in a state that can be described as liquid. Because the gel is not very viscous, it can reach all points on the surface of the part to be decontaminated, including the most difficult-to-access areas of parts with complex geometry.

[0100] In other words, the decontamination gel behaves like a liquid in the soaking bath and can thus infiltrate all parts of the part and cover all surfaces of the contaminated parts and even the most difficult to access surfaces.

[0101] The gel according to the invention is thus particularly suitable for the treatment of parts of small size and / or complex shape or geometry.

[0102] As soon as the gel-coated part is removed from the bath, the gel film covering the part, outside the bath, is subjected to the stimulus described above, which causes a very rapid, even almost instantaneous, increase in the viscosity of the gel film covering the part upon leaving the bath. The gel film then generally has sufficient viscosity to guarantee the adhesion of the gel film and prevent drips.

[0103] In other words, the gel which was in a liquid state in the bath, regains a gel-like structure as soon as the part is removed from the bath.

[0104] One of the major disadvantages of prior art liquid dipping baths in which no change in viscosity occurs when the part is removed from the bath is thus overcome.

[0105] The gel according to the invention may optionally comprise a super-absorbent polymer.

[0106] The incorporation of a super-absorbent polymer into a decontamination gel and a fortiori the combination in such a gel of such a super-absorbent polymer with a decontamination agent, such as a biological decontamination agent, and with a viscosity variation agent have never been described in the prior art, as represented in particular by the documents cited above.

[0107] The gel according to the invention is a colloidal solution, which means that the gel according to the invention contains inorganic, mineral, solid particles of viscosifying agent whose elementary, primary particles generally have a size of 2 to 200 nm.

[0108] Due to the use of a generally exclusively inorganic viscosifying agent, without organic viscosifying agent, the organic matter content of the gel according to the invention is generally less than 4% by mass, preferably less than 2% by mass, which constitutes yet another advantage of the gels according to the invention.

[0109] These solid, mineral, inorganic particles act as a viscosifier to allow the solution, for example the aqueous solution, to gel and thus adhere to the surfaces of the part to be treated, decontaminated, whatever their geometry, shape, size, and wherever the contaminants to be eliminated are located (see Example 6).

[0110] Advantageously, the inorganic viscosifying agent can be chosen from aluminas, silicas, aluminosilicates, clays such as smectite, and mixtures thereof.

[0111] In particular, the inorganic viscosifier can be chosen from aluminas (Al 2 O 3 ) and silicas (SiO 2 ).

[0112] The inorganic viscosifier may comprise only one silica or alumina or a mixture thereof, namely a mixture of two or more different silicas (SiO 2 / SiO 2 mixture), a mixture of two or more different aluminas (Al 2 O 3 / Al 2 O 3 mixture), or a mixture of one or more silicas with one or more aluminas (SiO 2 / Al 2 O 3 mixture).

[0113] Advantageously, the inorganic viscosifying agent may be chosen from pyrogenic silicas, precipitated silicas, hydrophilic silicas, hydrophobic silicas, acidic silicas, basic silicas such as Tixosil ®< 73 silica, marketed by the company Rhodia, and mixtures thereof.

[0114] Among the acid silicas, we can notably cite the pyrogenic or silica fume "Cab-O-Sil" ®< M5, H5 or EH5, marketed by the company CABOT, and the pyrogenic silicas marketed by the company DEGUSSA under the name AEROSIL ®<.

[0115] Among these pyrogenic silicas, we still prefer AEROSIL ® silica < 380 with a specific surface area of ​​380 m 2 < / g which offers maximum viscosity properties for a minimal mineral load.

[0116] The silica used can also be a so-called precipitated silica obtained for example by the wet process by mixing a sodium silicate solution and an acid. The preferred precipitated silicas are marketed by DEGUSSA under the name SIPERNAT ®< 22 LS and FK 310 or by the company RHODIA under the name TIXOSIL ®< 331, the latter being a precipitated silica whose average specific surface area is between 170 and 200 m 2 < / g.

[0117] Advantageously, the inorganic viscosifying agent consists of a mixture of a precipitated silica and a pyrogenic silica.

[0118] The alumina may be selected from calcined aluminas, ground calcined aluminas, and mixtures thereof.

[0119] For example, we can cite the product sold by DEGUSSA under the commercial name “Aeroxide Alumine C” which is fine pyrogenic alumina.

[0120] Advantageously, according to the invention, the viscosifying agent consists of one or more alumina(s) generally representing from 5% to 30% by mass relative to the mass of the gel.

[0121] In this case, the alumina is preferably at a concentration of 8% to 17% by mass relative to the total mass of the gel to ensure drying of the gel at a temperature between 20°C and 50°C and at a relative humidity between 20% and 60% on average in 30 minutes to 5 hours.

[0122] The nature of the mineral viscosifying agent, in particular when it is made up of one or more alumina(s), unexpectedly influences the drying of the gel according to the invention and the particle size of the residue obtained.

[0123] Indeed, the dry gel is in the form of particles of controlled size, more precisely solid millimetric flakes, the size of which generally ranges from 1 to 10 mm, preferably from 2 to 5 mm thanks in particular to the aforementioned compositions of the present invention, in particular when the viscosifying agent is constituted by one or more alumina(s).

[0124] Note that the size of particles generally corresponds to their largest dimension.

[0125] In other words, the solid mineral particles of the gel according to the invention, for example of the silica or alumina type, in addition to their role as viscosifiers, also play a fundamental role during the drying of the gel because they ensure the fracturing of the gel to result in a dry waste in the form of flakes (Example 7).

[0126] The gel according to the invention contains an active decontamination agent. This active decontamination agent may be any active decontamination agent capable of eliminating a contaminant regardless of the nature of this contaminant: whether this contaminant is chemical, biological or even nuclear, radioactive, or whether this contaminant is organic or mineral, liquid or solid; or regardless of the form of this contaminant: whether this contaminant is in a massive or particulate form, contained in a surface layer of the material of the part, in the form of a film or contained in a film, for example a film of grease on the surface of the part, in the form of a layer or contained in a layer, for example a layer of paint on the surface of the part, or simply deposited on the surface of the part.

[0127] Depending on the nature of the contamination, the modes of action of the gels differ: erosion of the support material containing the contamination, solubilization of the contaminating film, for example of grease, or covering, for example of paint, or even inactivation in situ chemical or biological contaminants in the case of pathogenic species (anthrax).

[0128] The gel according to the invention can thus contain an active biological or chemical or even nuclear radioactive decontamination agent; the active decontamination agent can also be a degreasing or stripping agent. Certain active decontamination agents can simultaneously perform several decontamination functions.

[0129] By biological decontamination agent, which can also be described as a biocidal agent, we mean any agent which, when brought into contact with a biological species, and in particular a toxic biological species, is capable of inactivating or destroying it.

[0130] By biological species, we mean any type of microorganism such as bacteria, fungi, yeasts, viruses, toxins, spores including Bacillus Anthracis spores, and protozoa.

[0131] The biological species which are eliminated, destroyed, inactivated, by the gel according to the invention are essentially bio-toxic species such as pathogenic spores such as for example Bacillus Anthracis spores, toxins such as for example botulinum toxin, and viruses.

[0132] A chemical decontamination agent means any agent which, when brought into contact with a chemical species, and in particular a toxic chemical species, is capable of destroying or inactivating it.

[0133] The chemical species which are eliminated by the gel according to the invention are in particular toxic chemical species such as toxic gases, in particular neurotoxic or vesicant gases.

[0134] These toxic gases include organophosphorus compounds, including Sarin or GB agent, VX, Tabun or GA agent, Soman, Cyclosarin, diisopropyl fluorophosphonate (DFP), Amiton or VG agent, Parathion, Dimethoxy methylphosphonate (DMMP). Other toxic gases include mustard gas or H agent or HD agent, Lewisite or L agent, and T agent.

[0135] The nuclear, radioactive species which can be eliminated by the gel according to the invention can be chosen for example from metal oxides and hydroxides, in particular in the form of solid precipitates.

[0136] It should be noted that in the case of radioactive species, we are not talking about destruction or inactivation but only about the elimination of contamination by dissolution of the irradiating deposits or corrosion of the materials supporting the contamination. There is therefore a real transfer of nuclear contamination to the dry gel flakes.

[0137] The active decontamination agent, for example the active biological or chemical decontamination agent, may be chosen from bases such as sodium hydroxide, potassium hydroxide, and mixtures thereof; acids such as nitric acid, phosphoric acid, hydrochloric acid, sulfuric acid, hydrogen oxalates such as sodium hydrogen oxalate, and mixtures thereof; oxidizing agents such as peroxides, permanganates, persulfates, ozone, hypochlorites, cerium IV salts and mixtures thereof; quaternary ammonium salts such as hexacetylpyridinium salts such as hexacetylpyridinium chloride; reducing agents; and mixtures thereof.

[0138] Some active decontamination agents can be classified into several of the categories defined above.

[0139] Thus, nitric acid is an acid but also an oxidizing agent.

[0140] When the gel contains carrageenans, the active decontamination agent is preferably chosen from sodium hydroxide, potassium hydroxide, sodium hydrogen oxalate, oxalic acid (Examples 8, 9 and 10) and mixtures thereof.

[0141] The active decontamination agent is preferably an oxidizing agent such as a peroxide or a cerium IV salt, when the stimulus mentioned above is a variation in the chemical redox potential.

[0142] The active decontamination agent, such as a biocidal agent, is generally used at a concentration of 0.5 to 10 mol / L of gel, preferably 1 to 10 mol / L, and more preferably 3 to 6 mol / L of gel in order to guarantee a decontamination power, for example a power of inhibition of biological species, in particular biotoxic species, compatible with the drying time of the gel, and to ensure for example drying of the gel at a temperature of between 20°C and 50°C and at a relative humidity of between 20% and 60% on average in 30 minutes to 5 hours.

[0143] In order to achieve total effectiveness, including under the most unfavorable temperature and humidity conditions with respect to drying time, the formulation of the gel of the present invention supports different concentrations of active agent. It can be noted, in fact, that increasing the concentration of decontamination agent, more particularly of acidic or basic or acidic decontamination agent, considerably increases the drying time of the gel and therefore the effectiveness of the process (Example 2). To take into account the erosion kinetics of the materials and the inhibition kinetics of the contaminating species, in particular biotoxic species, the active decontamination agent, in particular the biological decontamination agent, will preferably be present in the gel at a concentration of between 3 and 6 mol / l in order to achieve maximum effectiveness of the process.

[0144] The active decontamination agent may be an acid or a mixture of acids. These acids are generally chosen from mineral acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.

[0145] A decontaminating agent, particularly a particularly preferred biological decontaminating agent, is nitric acid.

[0146] In fact, it turned out, quite surprisingly, that nitric acid destroyed and inactivated biological species, particularly biotoxic ones.

[0147] In particular, it has been surprisingly demonstrated that nitric acid ensures the destruction, the inactivation, of spores such as those of Bacillus thuringiensis which are particularly resistant species.

[0148] The acid or acids is (are) preferably present at a concentration of 0.5 to 10 mol / L, more preferably 1 to 10 mol / L, better still 3 to 6 mol / L to ensure drying of the gel generally at a temperature between 20°C and 50°C and at a relative humidity between 20% and 60% on average in 30 minutes to 5 hours.

[0149] For this type of acid gel, the inorganic viscosifying agent is preferably silica or a mixture of silicas.

[0150] Alternatively, the active decontamination agent, for example the active biological decontamination agent, may be a base, preferably a mineral base, preferably chosen from soda, potash, and mixtures thereof.

[0151] In the case of such a basic gel formulation, the gel according to the invention has, in addition to the decontamination action, a degreasing action.

[0152] As already mentioned above, in order to achieve total effectiveness, including in the most unfavorable climatic conditions with regard to the drying time of the gel, the gel according to the invention can have a wide range of concentration of basic decontamination agent(s).

[0153] Indeed, increasing the concentration of basic decontamination agents such as NaOH or KOH, which generally act as biocidal agents, can significantly increase the inhibition rates of biological species, as has been demonstrated for Bacillus thuringiensis spores (Example 1).

[0154] The base is advantageously present at a concentration of less than 10 mol / L, preferably between 0.5 and 7 mol / L, more preferably between 1 and 5 mol / L, better still between 3 and 6 mol / L, to ensure drying of the gel at a temperature between 20°C and 50°C and at a relative humidity between 20% and 60% on average in 30 minutes to 5 hours.

[0155] For this type of alkaline, basic gel, the inorganic viscosifying agent is preferably an alumina or a mixture of aluminas.

[0156] In order to achieve maximum effectiveness on a wide range of materials while ensuring the safety of the treatment, the decontamination agent, particularly when it is a biological decontamination agent, is preferably sodium hydroxide or potassium hydroxide.

[0157] In the case of the treatment of a cement matrix, the basic pH of the gel, which is induced by the use of soda or potash, makes it possible to avoid acid-base reactions between the material to be decontaminated and the gel, which harm the integrity of the gel on the surface and therefore the effectiveness of the process.

[0158] The hygroscopic nature of sodium hydroxide or potassium hydroxide also constitutes a considerable advantage in slowing down the drying process of the gel. The contact time between the gel according to the invention, containing for example a biocidal solution, and the biological contamination is then considerably increased.

[0159] Indeed, the competition between the evaporation process of the aqueous phase and that of water uptake of the sodium hydroxide or potassium hydroxide crystals favorably modifies the drying kinetics of the gel (Example 2).

[0160] In view of the kinetics of spore inhibition (Example 1) and the drying times of the gels as a function of temperature, the active decontamination agent, particularly when it is a biocidal agent, will preferably be sodium hydroxide at a concentration of between 1 and 5 mol / L.

[0161] Advantageously, the gel according to the invention may also contain a super-absorbent polymer.

[0162] By "super-absorbent polymer" also called "SAP", we generally mean a polymer capable, in the dry state, of spontaneously absorbing at least 10 times, preferably at least 20 times its weight of aqueous liquid, in particular water and in particular distilled water.

[0163] Some "SAPs" can absorb up to and even more than 1000 times their weight in liquid.

[0164] Such super-absorbent polymers are notably described in the work "Absorbent Polymer Technology, Studies in Polymer Science 8" by L. BRANNON-PAPPAS and R. HARLAND, Elsevier edition, 1990, to which one can refer.

[0165] Spontaneous absorption means an absorption time of up to about one hour.

[0166] The superabsorbent polymer may have a water absorption capacity ranging from 10 to 2000 times its own weight, preferably from 20 to 2000 times its own weight (i.e. 20 g to 2000 g of water absorbed per gram of absorbent polymer), more preferably from 30 to 1500 times, and in particular from 50 to 1000 times.

[0167] These water absorption characteristics apply under normal temperature (25°C) and pressure (760 mm Hg or 100,000 Pa) conditions and for distilled water.

[0168] The SAP of the decontamination gel according to the invention can be chosen from sodium poly(meth)acrylates, starches grafted with a (meth)acrylic polymer, hydrolyzed starches grafted with a (meth)acrylic polymer; polymers based on starch, gum, and cellulose derivative; and mixtures thereof.

[0169] More specifically, the SAP usable in the gel according to the invention can be chosen, for example, from: polymers resulting from the polymerization with partial crosslinking of water-soluble ethylenically unsaturated monomers, such as acrylic, methacrylic (in particular from the polymerization of acrylic and / or methacrylic acid and / or acrylate and / or methacrylate monomers) or vinyl polymers, in particular crosslinked and neutralized poly(meth)acrylates, in particular in gel form; and salts, in particular alkali salts such as sodium or potassium salts of these polymers; starches grafted with polyacrylates; acrylamide / acrylic acid copolymers, in particular in the form of sodium or potassium salts; acrylamide / acrylic acid grafted starches, in particular in the form of sodium or potassium salts; sodium or potassium salts of carboxymethylcellulose; salts, in particular alkali salts, of crosslinked polyaspartic acids; salts, in particular alkali salts, of crosslinked polyglutamic acids.

[0170] In particular, a compound chosen from: les polyacrylates de sodium ou de potassium réticulés vendus sous les dénominations SALSORB CL 10, SALSORB CL 20, FSA type 101, FSA type 102 (Allied Colloids) ; ARASORB S-310 (Arakawa Chemical) ; ASAP 2000, Aridall 1460 (Chemdal) ; KI-GEL 201-K (Siber Hegner) ; AQUALIC CA W3, AQUALIC CA W7, AQUALIC CA W10; (Nippon Shokuba) ; AQUA KEEP D 50, AQUA KEEP D 60, AQUA KEEP D 65, AQUA KEEP S 30, AQUA KEEP S 35, AQUA KEEP S 45, AQUA KEEP Al M1, AQUA KEEP AI M3, AQUA KEEP HP 200, NORSOCRYL S 35, NORSOCRYL FX 007 (Arkema) ; AQUA KEEP 10SH-NF, AQUA KEEP J-550 (Kobo); LUQUASORB CF, LUQUASORB MA 1110, LUQUASORB MR 1600, HYSORB C3746-5 (BASF) ; COVAGEL (Sensient technologies), SANWET IM-5000D (Hoechst Celanese) ; les polyacrylates greffés d'amidon vendus sous les dénominations SANWET IM-100, SANWET IM-3900, SANWET IM-5000S (Hoechst) ;starch-grafted acrylamide / acrylic acid copolymers in sodium or potassium salt form sold under the names WATERLOCK A-100, WATERLOCK A-200, WATERLOCK C-200, WATERLOCK D-200, WATERLOCK B-204 (Grain Processing Corporation); acrylamide / acrylic acid copolymers in sodium salt form sold under the name WATERLOCK G-400 (Grain Processing Corporation); carboxymethylcellulose sold under the name AQUASORB A250 (Aqualon); crosslinked sodium polyglutamate sold under the name GELPROTEIN (Idemitsu Technofine).

[0171] Superabsorbent polymers, in particular superabsorbent polymers (polyelectrolytes) which contain alkaline ions such as sodium or potassium ions, for example of the sodium or potassium poly(meth)acrylate type, confer numerous properties to the decontamination gels according to the invention.

[0172] They first influence the rheology of the product, in particular its flow threshold. In terms of process implementation, the advantage of super-absorbent polymers is to guarantee perfect adhesion of the gel on the treated materials, in particular on vertical and overhanging surfaces when the thickness of the sprayed gel is greater than 1 mm.

[0173] In the context of a decontamination process, particularly biological decontamination by gel, the super-absorbent polymer is particularly interesting because it absorbs by hydrogen bonding a part of the solution, for example the biocidal solution contained in the gel. The number of hydrogen bonds formed between the solution, for example the biocidal solution, of the gel and the super-absorbent polymer such as sodium polyacrylate being a function of the saline load, absorption / desorption phenomena appear when the saline load of the decontamination gel is modified.

[0174] This mechanism is therefore particularly interesting when it comes to decontaminating mineral and porous materials such as cement matrices for example.

[0175] Indeed, upon contact with the material, the saline load of the gel increases due to the presence of mineral particles, very often calcium-based. Within the super-absorbent polymer such as sodium polyacrylate, the substitution of the counter-ion Na +< by Ca 2+< from calcium instantly generates a phenomenon of re-release of solution, for example of biocide solution, due to the greater steric hindrance of the calcium ion.

[0176] The amount of solution, for example biocide solution released by the super-absorbent polymer such as sodium polyacrylate can then diffuse instantly into the porosity of the material and penetrate deep down.

[0177] The phenomenon of diffusion of the decontamination agent, for example the biocidal agent towards the heart of the material is much more limited in the case of a gel not containing super-absorbent (see Figures 2 and 3 ).

[0178] The addition of super-absorbent polymer to the gel according to the invention therefore makes it possible to significantly increase the effectiveness of the gel and of the method according to the invention in the presence of porous materials contaminated in depth over a thickness of one to several millimeters, for example up to 2, 5, 10, 20 or even 100 mm (Example 3).

[0179] The super-absorbent polymer can preferably be chosen from the Aquakeep ® or Norsocryl ® ranges marketed by the company ARKEMA.

[0180] The gel may also contain a surfactant or a mixture of surfactants, preferably chosen from the family of non-ionic surfactants such as block copolymers, sequenced copolymers such as block copolymers of ethylene oxide and propylene oxide, and ethoxylated fatty acids; and mixtures thereof.

[0181] For this type of gel, the surfactants are preferably block copolymers marketed by BASF under the name "PLURONIC ®< ".

[0182] Pluronics ®< are block copolymers of ethylene oxide and propylene oxide.

[0183] These surfactants influence the rheological properties of the gel, in particular the thixotropic nature of the product and its recovery time, and prevent the appearance of dripping.

[0184] Surfactants also make it possible to control the adhesion of dry waste (Example 4) and to control the size of the dry residue flakes to ensure that the waste is not powdery (Example 5).

[0185] The solvent according to the invention is generally chosen from water, organic solvents, and their mixtures.

[0186] A preferred solvent is water, and in this case the solvent is therefore water, comprising 100% water.

[0187] The invention further relates to a method for decontaminating at least one surface of a part made of a solid material, said surface being contaminated by at least one contaminating species located on said surface and possibly under said surface in the depth of the part, in which at least one cycle is carried out comprising the following successive steps: a) the part is immersed in a bath of the gel as described above in the liquid state with a viscosity of less than 0.1 Pa.s; b) the part, coated with a film of the gel, is removed from the bath and immediately subjected to at least one stimulus which causes an increase in the viscosity of the gel in a period of less than 5 seconds and its transition to a gelled state with a viscosity greater than 100 Pa.s; c) the gel is maintained on the contaminated surface at least for a period of time sufficient for the gel to destroy and / or inactivate and / or absorb the contaminating species, and for the gel to dry and form a dry, solid residue containing said contaminating species; d) the dry, solid residue containing said contaminating species is removed.

[0188] In step b), the rapid increase in viscosity is generally due mainly or even solely to the action of the stimulus on the viscosity-varying agent.

[0189] Generally, the stimulus has little or no effect on other components of the gel, such as the solvent, and does not usually cause the latter to be eliminated, and this rapid increase in viscosity is therefore generally not due to solvent elimination.

[0190] Said stimulus has already been described in detail above and can be chosen from chemical stimuli such as a variation in the oxidation-reduction potential of the gel; thermal such as a variation in the temperature of the gel; physical such as exposure to an electromagnetic wave; and combinations of two or more of said stimuli.

[0191] If the stimulus is an increase in the temperature of the gel, it generally acts mainly, or even solely, on the viscosity-varying agent and consequently causes a rapid increase in the viscosity of the gel, due mainly, or even solely, to this action of the stimulus on the viscosity-varying agent. This stimulus does not generally act on the solvent and does not generally cause its elimination. The rapid increase in viscosity during step b) is therefore generally not due to a removal of the solvent such as that achieved during the drying step.

[0192] Advantageously, said stimulus is a decrease in temperature, caused for example by the passage of the part from a heated bath, for example at a temperature of 30°C to 80°C to the ambient atmosphere, for example at a temperature of 15°C to 25°C; or said stimulus is the start of the exposure of the gel to a magnetic field or the stopping of the exposure of the gel to a magnetic field.

[0193] Therefore, the magnetic field can be applied to the tank containing the liquid gel or, on the contrary, around the part that has just been coated.

[0194] The increase in the viscosity of the gel during step b) occurs in a time of less than 5 seconds, preferably less than 2 seconds, more preferably less than or equal to 1 second, for example in a time of between 0.5 seconds and 1 second.

[0195] It should be noted that the rapid increase in the viscosity of the gel and its transition from a liquid to a gelled state which occurs during step b) should not be confused with the drying which occurs during step c).

[0196] Indeed, the transition from a liquid state to a gelled state of the gel during step b) generally occurs without the solvent being removed. In other words, the solvent contents of the gel in the liquid state and the gel in the gelled state are generally substantially identical even if the stimulus is an increase in temperature. On the contrary, during the drying carried out during step c), the solvent is removed to form a dry and solid residue which is no longer a gel in the liquid or gelled state.

[0197] Advantageously, the part is a small part and / or a complex shape.

[0198] It should be noted that, in the case of a non-porous surface, contamination, for example "inactivated" biological contamination, is recovered by the dry gel flakes.

[0199] On the other hand, in the case of deep contamination, as is the case in porous materials such as cement matrices, the dry gel will only contain the surface contamination residue.

[0200] Internal, deep, “inactivated” contamination in situ following the action of the superabsorbent which is then advantageously incorporated into the gel, will remain at the heart of the material, substrate.

[0201] Advantageously, the solid substrate is a porous substrate, preferably a porous mineral substrate and the gel according to the invention then advantageously contains a superabsorbent polymer.

[0202] However, the effectiveness of the gel and the method according to the invention is just as good in the presence of a non-porous and / or non-mineral surface.

[0203] Advantageously, the substrate is made of at least one material chosen from metals and metal alloys such as stainless steel, aluminum, lead; polymers such as plastics or rubbers such as poly(vinyl chloride)s or PVC, polypropylenes or PP, polyethylenes or PE in particular high density polyethylenes or HDPE, poly(methyl methacrylate)s or PMMA, poly(vinylidene fluoride)s or PVDF, polycarbonates or PC; glasses; cements and cementitious materials; mortars and concretes; plasters; bricks; natural or artificial stone; ceramics.

[0204] Advantageously, the contaminating species is chosen from the chemical, biological, nuclear or radioactive contaminating species already listed above and in particular from the toxic biological species already listed above.

[0205] Advantageously, the gel is applied to the surface to be decontaminated at a rate of 100 g to 2000 g of gel per m 2< of surface, preferably 500 to 1500 g of gel per m 2< of surface, more preferably 600 to 1000 g per m 2< of surface, which generally corresponds to a thickness of gel deposited on the surface of between 0.5 mm and 2 mm.

[0206] Advantageously (during step c)), the drying is carried out at a temperature of 1°C to 50°C, preferably 15°C to 25°C, and at a relative humidity of 20% to 80%, preferably 20% to 70%.

[0207] Advantageously, the gel is maintained on the surface for a period of 2 to 72 hours, preferably 2 to 48 hours, more preferably 5 to 24 hours.

[0208] Advantageously, the dry and solid residue is in the form of particles, for example flakes, with a size of 1 to 10 mm, preferably 2 to 5 mm.

[0209] Advantageously, the dry and solid residue is removed from the solid surface by brushing and / or vacuuming.

[0210] Advantageously, the cycle described above can be repeated, for example, from 1 to 10 times using the same gel in all cycles or using different gels in one or more cycle(s).

[0211] Advantageously, during step c), the gel, before complete drying, is re-wetted with a solution of a decontamination agent, preferably with a solution of the active agent for decontaminating the gel from the bath of step a) in the solvent of this gel, which then generally avoids repeating the application of the gel to the surface and results in savings in reagent and a limited quantity of waste. This re-wetting operation can be repeated, for example, from 1 to 10 times.

[0212] The method according to the invention has all the advantageous properties inherent in the decontamination gel that it uses and which have already been widely explained above.

[0213] The method according to the invention uses a gel for the first time in a soaking decontamination process.

[0214] The method according to the invention has all the advantages of methods which use a gel and in particular a suctionable gel such as that described in documents [9] and

[10] but does not have the disadvantages of these methods because the application of the gel is, in the method according to the invention, carried out by soaking, immersion in the gel in the liquid state which makes it possible for the first time to treat and decontaminate parts of small size and / or complex shape or geometry.

[0215] In the same way, the method according to the invention has the advantages of decontamination methods by soaking, immersion but without their disadvantages. Indeed, in the method according to the invention, as soon as the part covered with a film of liquid gel is removed from the bath, said gel takes a gelled form under the action of the stimulus, all risks of dripping, spreading and dissemination of contaminants are avoided.

[0216] Compared to decontamination processes by soaking in liquid solutions (which do not exhibit a transition between a liquid phase and a gelled phase under the action of a stimulus), the fact that the decontamination product is, according to the invention, in a gelled form constitutes a real advantage for significantly reducing the volume of highly contaminated waste.

[0217] Indeed, once the operation of coating the part with the gel in the liquid state has been carried out - by very brief immersion in the bath - the actual decontamination phase - that is to say the phase during which the film of gel in the gelled state deposited will interact with the contaminated surface - is carried out outside the bath, thus avoiding contamination of the latter.

[0218] At the end of a drying phase identical to that of the so-called "vacuum gel process" in documents [9] and

[10] , the contamination is trapped in a very limited quantity - for example less than 200 g / m 2 of treated surface - of dry gel flakes which can be easily eliminated.

[0219] In summary, the method and the gel according to the invention have, among other things, the following advantageous properties: the application of the gel by dipping the parts in a gel bath in low-viscosity liquid form (coating), whereby the gel infiltrates and covers all the surfaces of the parts even when these parts are small and / or have complex geometries; adhesion to the walls of the part as soon as they come out of the bath; obtaining maximum decontamination efficiency at the end of the gel drying phase, including in situations of penetrating contamination, particularly in the case of porous surfaces, in which case the gel advantageously contains a superabsorbent polymer;

[0220] Generally, the drying time is greater than or equal to the time required to inactivate the contaminating species. In the case of deep inactivation, rewetting is generally used. the processing of a very wide range of materials; the absence of mechanical or physical alteration of the materials at the end of the processing, the implementation of the process in variable climatic conditions, the reduction of the volume of waste, the ease of recovery of dry waste.

[0221] Other characteristics and advantages of the invention will appear better on reading the detailed description which follows, this description being given for illustrative and non-limiting purposes, in conjunction with the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS.

[0222] There Figure 1 (A, B) shows schematic sectional views illustrating the main steps of the method according to the invention for the decontamination of a solid material. The Figure 2 (A, B, C) shows schematic cross-sectional views showing the mode of action of a superabsorbent polymer-free gel on a cementitious material deeply contaminated by liquid contamination. Figure 3 (A, B, C) shows schematic cross-sectional views showing the mode of action of a gel containing a super-absorbent polymer on a cementitious material deeply contaminated by liquid contamination. The Figure 4 (A, B) shows the structures of κ-carrageenans (A) and (B). The Figure 5 presents the conformations that carrageenan chains take as a function of temperature and ionic charge in the medium. Figure 6 is a diagram of a process for obtaining ferromagnetic silica particles which comprise a magnetic iron oxide core and a silica shell. Figure 7, which illustrates Example 1, is a graph representing the inhibition kinetics of Bacillus thuringiensis spores in different liquid biocidal solutions containing different bases at various concentrations, namely: 0.5 M NaOH, 1 M NaOH, 5 M NaOH, 0.5 M KOH, 1 M KOH, and 5 M KOH. The number of residual spores is given for each of the biocidal solutions at contact times of 1 hour, 2 hours, 3 hours, 4 hours, and 5 hours. Figure 8 , which illustrates Example 2, is a graph that represents the influence of the sodium hydroxide concentration in the gel on the drying time.

[0223] The mass loss of the gel in % is plotted on the ordinate and the drying time of the gel in days is plotted on the abscissa.

[0224] Curves A, B, C, and D represent gel drying without NaOH (water only), and with NaOH concentrations of 1M, 5M, and 10M, respectively. - - There Figure 9, which illustrates Example 3, is a graph that represents the influence of the super-absorbent polymer on the effectiveness of biological decontamination of a mortar expressed by the number of Bacillus thuringiensis spores on a mortar sample.

[0225] For each gel, the left bars (light gray A and B) represent the contamination of the mortar samples before treatment, and the right bars (dark gray C and D) represent the residual contamination of the mortar samples after recovery from the dry gel.

[0226] The graph shows two separate gel treatments, the first (left part of the graph, bars A and C next to the left of the graph) in the presence of a biocidal gel free of superabsorbent polymer, the second (right part of the graph, bars B and D next to the right of the graph) in the presence of the same biocidal gel to which the superabsorbent polymer has been added. There Figure 10, which illustrates example 4, is a graph which represents the influence of the surfactant concentration (Pluronic ®< ) on the adhesion power of dry gel flakes.

[0227] The total adhesion area (mm 2 < / cm 2 < ) is plotted on the ordinate, and the surfactant concentration (g / L) is plotted on the abscissa. There Figure 11 , which illustrates example 5, is a graph that represents the influence of the surfactant concentration (Pluronic ®< ) on the number of dry gel flakes formed.

[0228] The number of flakes / cm 2 is plotted on the ordinate, and the surfactant concentration (g / L) is plotted on the abscissa. There Figure 12 , which illustrates example 6, is a graph which gives the evolution of the viscosity of two gels as a function of temperature.

[0229] The first gel whose viscosity is represented by curve A is an aqueous gel which contains 9% by mass of silica but which does not contain carrageenan.

[0230] The second gel whose viscosity is represented by curve B is an aqueous gel which contains 0.6% by mass of - Carrageenan but which does not contain silica.

[0231] The viscosity η 0 (in Pa.s) is plotted on the ordinate, and the temperature T (in °C) is plotted on the abscissa. There Figure 13 (A, B), which illustrates example 7, presents two photographs which show the influence of silica on the morphology of a gel after drying.

[0232] Figure (A) shows the morphology after drying of an aqueous gel containing 1.2% by mass of - Carrageenan but no silica, and Figure (B) shows the morphology after drying of an aqueous gel containing 1.2% by mass of - Carrageenan and 9% by mass of silica. There Figure 14 (A, B), which illustrates Example 8, presents two photographs which show the erosion generated by a coating gel according to the invention comprising saturated sodium hydrogen oxalate and 1.4% by mass of κ-Carrageenan applied to a black steel plate. - The Figure 15 , which illustrates Example 9, is a graph which gives the thickness (in mm) of black steel degraded by a coating gel according to the invention comprising saturated sodium hydrogen oxalate and 1.4% by mass of κ-Carrageenan applied to a black steel plate.

[0233] The measurement is carried out using an optical profilometer. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0234] The gel according to the invention can be easily prepared generally at room temperature.

[0235] For example, the gel according to the invention can be prepared by adding, preferably gradually, the inorganic viscosifying agent(s), for example alumina(s) and / or silica(s), to a solution containing the active decontamination agent(s), the viscosity variation agent(s), and the super-absorbent polymer(s).

[0236] The said solution is generally a lukewarm solution, that is to say it has been brought to a temperature generally of 30°C to 80°C.

[0237] This addition can be carried out by simply pouring the inorganic viscosifying agent(s) into said solution. When adding the inorganic viscosifying agent(s), the solution containing the active decontamination agent(s), the viscosity varying agent(s), and the super-absorbent polymer(s) is generally maintained under mechanical stirring. This stirring can be carried out, for example, by means of a mechanical stirrer equipped with a three-bladed propeller.

[0238] The stirring speed is generally between 600 and 800 rpm.

[0239] Finally, the surfactant(s) are added, generally while maintaining mechanical agitation.

[0240] After the addition of the surfactant(s), stirring is continued, for example for 2 to 5 minutes, so as to obtain a perfectly homogeneous gel.

[0241] It is obvious that other protocols for preparing the gels according to the invention can be implemented with an addition of the gel components in a different order from that mentioned above.

[0242] Generally, the gel according to the invention when it is in the bath and before any application of a stimulus is in a liquid, low-viscosity state and must therefore generally have a viscosity of less than 100 mPa.s under “zero” shear, i.e. generally less than 5s -1< ). The liquid, low-viscosity gel can thus infiltrate into all the corners of the part and reach all the surfaces of the contaminated parts, even the most difficult to access.

[0243] The viscosity recovery time upon leaving the bath and following the application of a stimulus must generally be less than 5 seconds, preferably less than 2 seconds, more preferably less than or equal to 1 second, for example between 0.5 seconds and 1 second and the viscosity of the gel under low shear must generally be greater than 10 Pa.s so that the gel adheres to the surfaces and does not flow.

[0244] It should be noted that the surfactant of the gel according to the invention favorably and significantly influences the rheological properties of the gel according to the invention. This surfactant makes it possible in particular to avoid the risks of spreading or running.

[0245] The gel according to the invention thus prepared is then applied (1) ( Figure 1) on the solid surface (2) to be decontaminated from a substrate made of a solid material (3), in other words on the surface (2) having been exposed to contamination, for example to biological contamination (4); this contamination has already been described above. In particular, the biological contamination (4) may consist of one or more of the biological species already defined above.

[0246] As already indicated above, the active decontamination agent, for example the active biological decontamination agent, is chosen according to the contaminating species, for example the biological species to be eliminated, destroyed, or inactivated.

[0247] Except possibly for light metal alloys of the aluminium type, in the case where basic or acid gels are used, there is no limitation as to the material which constitutes the surface (2) to be decontaminated, in fact, the gel according to the invention makes it possible to treat without any damage, all kinds of materials, even fragile ones.

[0248] The gel according to the invention generally does not generate any alteration, erosion, attack, chemical, mechanical or physical of the treated material. The gel according to the invention is therefore in no way detrimental to the integrity of the treated materials and even allows their reuse. Thus, sensitive materials such as military equipment are preserved and can be reused after decontamination, while the monuments treated by the gel according to the invention are absolutely not degraded and see their visual and structural integrity preserved.

[0249] This substrate material (3) can therefore be chosen from, for example, metals and alloys such as stainless steel, aluminum, and lead; polymers such as plastics or rubbers, among which PVC, PP, PE, in particular HDPE, PMMA, PVDF, PC can be mentioned; glasses; cements and cementitious materials; mortars and concretes; plasters; bricks; natural or artificial stone; ceramics.

[0250] In all cases, whatever the material, the effectiveness of decontamination by the gel according to the invention is total.

[0251] The treated surface can be painted or unpainted.

[0252] Particularly surprisingly, it turned out that the gel according to the invention, when it contained a super-absorbent polymer, was particularly effective on porous materials such as cement matrices such as pastes, mortars and concretes, bricks, plasters, or even natural or artificial stone.

[0253] Indeed, the presence in the gel according to the invention of a super-absorbent polymer allows decontamination of the porous material over a much greater depth than with an equivalent gel without super-absorbent polymer.

[0254] In other words, the presence of a super-absorbent polymer in the gel according to the invention facilitates the diffusion of the active decontamination agent, for example the biocidal agent into the depth of the material when treating porous substrates, particularly mineral ones.

[0255] The effectiveness of the treatment with the gel according to the invention is generally total, including on materials contaminated over several millimeters in depth; in the latter case a super-absorbent polymer is then included in the gel.

[0256] There is also no limitation as to the shape, geometry and size of the part to be decontaminated, the gel according to the invention and the method implementing it allow in particular and advantageously the treatment of parts of small sizes and / or complex shapes and geometries.

[0257] A small room is generally understood to mean a room whose largest dimension is less than or equal to 2 meters, preferably less than or equal to 1 meter.

[0258] A part with a complex shape or geometry is generally understood to mean a part with, for example, hollows, angles, nooks, recesses, etc.

[0259] The gel according to the invention ensures effective treatment not only of horizontal surfaces of parts but also of vertical surfaces or inclined surfaces of these parts, or even of overhanging surfaces of these parts.

[0260] The gel according to the invention is applied to the surface to be treated by simple immersion, dipping the part in a bath containing the gel in the liquid state, weakly viscous, that is to say generally having the viscosity specified above.

[0261] During this immersion, soaking, the part and in particular the surface(s) to be decontaminated is (are) covered with a film of gel in a liquid state.

[0262] Soaking, immersion is usually of very short duration, for example, from 1 second to 60 seconds.

[0263] In fact, it can be considered that once the part is completely immersed in the bath in the liquid state, it is then immediately removed from the bath.

[0264] The part, coated, covered with a gel film for example 1 mm thick, taken out of the bath, is immediately subjected to at least one stimulus which causes a recovery of the gel, i.e. a rapid increase in the viscosity of the gel in the liquid state. The gel therefore passes from a liquid state to a truly gelled state, i.e. with a gel-like structure. In this gelled state, the gel film adheres to the surfaces of the part and does not flow.

[0265] The sufficiently short viscosity recovery time, namely generally less than 5 seconds, preferably less than 2 seconds, more preferably less than or equal to 1 second, for example between 0.5 seconds and 1 second, of the gels according to the invention, after application of the stimulus at the outlet of the liquid gel bath, allows the gels according to the invention to adhere to all surfaces of the parts to be decontaminated regardless of the arrangement or conformation of these surfaces.

[0266] This prevents any leakage or spreading of chemical solutions into the environment, and any dissemination or dispersion of contaminating species.

[0267] In other words, the particular rheological properties of the formulation, decontaminating composition according to the invention, allow the gel to (re)take, as soon as it leaves the soaking bath and almost instantly, a sufficient viscosity which guarantees the adhesion of the gel film to the surface and the drips.

[0268] The quantity of gel deposited on the surface to be treated at the exit of the bath is generally from 100 to 2000 g / m 2< , preferably from 500 to 1500 g / m 2< , more preferably from 600 to 1000 g / m 2< .

[0269] The amount of gel deposited per unit area and, consequently, the thickness of the gel deposited on the surface influences the drying rate.

[0270] Thus, when the film, layer of gel has a thickness of 0.5 mm to 2 mm, in particular 1 mm on the surface to be treated, the effective contact time between the gel and the materials is then equivalent to its drying time, period during which the active ingredient contained in the gel will interact with the contamination.

[0271] Furthermore, it has been surprisingly shown that the quantity of gel deposited when it is within the ranges mentioned above and in particular when it is greater than 500 g / m 2< and in particular in the range of 500 to 1500 g / m 2< , which corresponds to a minimum thickness of gel deposited for example greater than 500 µm for a quantity of gel deposited greater than 500 g / m 2< , made it possible, after drying of the gel, to obtain a fracturing of the gel in the form of millimetric flakes, for example of a size of 1 to 10 mm, preferably of 2 to 5 mm, which can be sucked up.

[0272] The amount of gel deposited and therefore the thickness of gel deposited, preferably greater than 500 g / m 2 < or 500 µm, is the fundamental parameter which influences the size of the dry residues formed after drying of the gel and which thus ensures that dry residues of millimetric size and not powdery residues are formed, such residues being easily removed by a mechanical process and preferably by suction.

[0273] However, it is also noted that thanks to the surfactant at low concentration, generally from 0.1% to 2% of the total mass of the gel, the drying of the gel is improved and leads to a homogeneous fracturing phenomenon with a mono-dispersed size of the dry residues and an increased ability of the dry residues to detach from the support.

[0274] The gel is then kept on the surface to be treated from the moment it leaves the bath and for the entire time necessary for it to dry. During this drying step, which can be considered to constitute the active phase of the process according to the invention or decontamination phase, the solvent contained in the gel, generally the water contained in the gel, evaporates until a dry, solid residue is obtained.

[0275] It should be noted that in the method according to the invention, the decontamination phase is carried out entirely outside the soaking bath and the latter is therefore not contaminated and can be used a very large number of times.

[0276] The drying time depends on the composition of the gel in the concentration ranges of its constituents given above, but also, as already specified, on the quantity of gel deposited per unit of surface, i.e. the thickness of gel deposited.

[0277] The drying time also depends on climatic conditions, namely the temperature and relative humidity of the atmosphere in which the solid surface is located.

[0278] The method according to the invention can be implemented under extremely wide climatic conditions, namely at a temperature T of 1°C to 50°C and at a relative humidity RH of 20% to 80%.

[0279] The drying time of the gel according to the invention is therefore generally from 1 hour to 24 hours at a temperature T of 1°C to 50°C and at a relative humidity RH of 20% to 80%.

[0280] It should be noted that the formulation of the gel according to the invention, essentially due to the presence of surfactants such as "Pluronics ®<", generally ensures a drying time which is substantially equivalent to the contact time (between the decontamination agent, such as a biocidal agent, and the contaminating species, for example the biological species, in particular biotoxic species to be eliminated) which is necessary, required to inactivate and / or absorb the contaminating species polluting the material and / or to sufficiently carry out the surface erosion reactions of the material.

[0281] In other words, the formulation of the gel ensures a drying time which is none other than the inactivation time of the contaminating species, for example biological species which is compatible with the kinetics of inhibition of the contamination for example biological contamination.

[0282] Or the gel formulation ensures a drying time which is none other than the time required for erosion reactions to remove a contaminated surface layer of the material.

[0283] In the case of radioactive contaminant species, the contamination is eliminated by dissolution of the irradiating deposits or by corrosion of the materials supporting the contamination. There is therefore a real transfer of nuclear contamination to the dry gel flakes.

[0284] The specific surface area of ​​the mineral filler generally used, which is generally 50 m 2 < / g to 300 m 2 < / g, preferably 100 m 2 < / g, and the absorption capacity of the gel according to the invention, make it possible to trap the labile (surface) and fixed contamination of the material constituting the surface to be treated.

[0285] If present, contaminating species, e.g., biological contaminating species, are inactivated in the gel phase. After drying the gel, the contamination, e.g., inactivated biological contamination, is removed during the recovery of the dry gel residue described below.

[0286] After drying the gel, the gel fractures homogeneously to give millimetric solid dry residues, for example of a size of 1 to 10 mm, preferably of 2 to 5 mm non-powdery, generally in the form of solid flakes (5) ( Figure 1B ).

[0287] Dry residues may contain the inactivated contaminant species(s) (6).

[0288] Dry residues, such as flakes (5), obtained after drying have low adhesion to the surface (2) of the decontaminated material. Therefore, the dry residues obtained after drying the gel can be easily recovered by simple brushing and / or vacuuming. However, dry residues can also be evacuated by gas jet, for example by compressed air jet.

[0289] Thus, no liquid rinsing is generally necessary and the process according to the invention generally does not generate any secondary effluent.

[0290] However, although not preferred, if desired, dry residue can be removed using a jet of liquid.

[0291] The method according to the invention therefore firstly achieves a significant saving in chemical reagents compared to a decontamination method by washing with a solution. Then, because waste is obtained in the form of a directly aspirable dry residue, a rinsing operation with water or with a liquid, generally necessary to eliminate traces of chemical agents from the part, is generally avoided. This obviously results in a significant reduction in the quantity of effluent produced but also a notable simplification in terms of the waste treatment system and outlet.

[0292] Due to the predominantly mineral composition of the gel according to the invention and the small quantity of waste produced, the dry waste can be stored or directed to a disposal channel ("outlet") without prior treatment. The dry gel flakes obtained from the process according to the invention have been approved by ANDRA as heterogeneous waste that can be immobilized in an HTC mortar grout.

[0293] At the end of the process according to the invention, solid waste is recovered in the form of flakes which can be packaged as is, directly packaged, resulting, as already indicated above, in a significant reduction in the quantity of effluent produced as well as a notable simplification in terms of the waste treatment process and outlet.

[0294] Furthermore, in the nuclear field, the fact of not having to reprocess the flakes before conditioning the waste constitutes a considerable advantage; this authorizes the use of high-performance active agents previously prohibited in liquid decontamination baths due to the operating constraints of liquid effluent treatment plants ("STEL").

[0295] The gel bath may therefore contain powerful oxidizing agents. These can, if necessary, be regenerated in situ by means of electrodes implanted in the bath. This is the case of cerium IV which can very easily be regenerated from the electrolysis of cerium III.

[0296] For example, in the common case where 1000 grams of gel are applied per m2 of treated surface, the mass of dry waste produced is less than 200 grams per m2.

[0297] On the Figure 2, the decontamination by a gel not containing super-absorbent polymer of a porous substrate (21) contaminated, for example by spores in aqueous solution (22) is illustrated. The contamination front (23) extends into the depth of the substrate ( Figure 2A ). When a biocidal gel (24) is applied to the surface (25) of the substrate, the diffusion front (26) of the biocidal agent extends little into the depth of the substrate and remains below the contamination front (23) ( Figure 2B ). Therefore, when the gel is removed ( Figure 2C ) the remediated zone (27) extends little in depth and there remains residual contamination (28) in the porous substrate (21).

[0298] On the Figure 3 , the decontamination, by a gel containing a super-absorbent polymer, of a porous substrate (31) contaminated, for example by spores in aqueous solution (32) is illustrated. The contamination front (33) extends into the depth of the substrate ( Figure 3A). When a biocidal gel containing the superabsorbent(34) is applied to the surface (35) of the substrate, the diffusion front (36) of the biocidal agent extends into the depth of the substrate and goes beyond the contamination front ( Figure 3B ). As a result, the cleaned zone (37) extends in depth (P) and there is no residual contamination left in the porous substrate.

[0299] The invention will now be described with reference to the following examples, given for illustrative and non-limiting purposes. EXAMPLES : Example 1 :

[0300] In this example, the inhibition kinetics of Bacillus thuringiensis spores are studied in different liquid biocide solutions containing different bases at various concentrations, namely: 0.5 M NaOH, 1 M NaOH; 5 M NaOH, 0.5 M KOH, 1 M KOH, and 5 M KOH. Experimental protocol :

[0301] The experiment consists of bringing 2x10 6< spores into contact with 1 ml of liquid biocide solution, while stirring.

[0302] After 1 hour, 2 hours, 3 hours, 4 hours, and 5 hours of stirring, samples of the mixture are taken to reveal the biological activity of the mixture and determine the kinetics of inhibition of the spores in the biocidal medium considered.

[0303] The revelation then consists of placing a drop of mixture on a nutrient medium (Agar Gel) and counting, after an incubation period of 16 hours at 30°C, the number of colonies formed. Each colony is the result of an inactivated spore.

[0304] The test results are given on the Figure 7 where the number of residual spores is given for each of the biocidal solutions at contact times of 1 hour, 2 hours, 3 hours, 4 hours, 5 hours.

[0305] There Figure 7shows that increasing the concentration of biocidal agent significantly increases the inhibition rates of Bacillus thuringiensis spores. Example 2:

[0306] In this example, we study the influence of the sodium hydroxide concentration in a gel (on the drying time).

[0307] The gel has the following composition in mass percentages: Alumina: 14% Sodium hydroxide solution (variable concentration): 85% Surfactant (Pluronic ®< P8020): 0.7% Super-absorbent polymer: Sodium polyacrylate Norsocryl ®< S35: 0.3%. Experimental protocol :

[0308] The gels, with varying sodium hydroxide concentrations (0 M, 1 M, 5 M and 10 M), are spread on an inert metal support to a controlled thickness of 1 mm. The metal support containing the gel film is then placed in a climatic chamber equipped with a precision balance that monitors the mass loss of the gel over time. The climatic chamber is regulated at a temperature of 22°C and a relative humidity of 60%.

[0309] The curves of the Figure 8 show that the hygroscopic nature of sodium hydroxide (but also potassium hydroxide) slows down the drying process of the gel. As a result, the contact time between the decontamination agent, namely the biocide solution, and the biological contamination is considerably increased.

[0310] This example is not carried out with a gel conforming in all respects to the gel according to the invention, however the results of this example can also be applied to a gel according to the invention.

[0311] The effect of sodium hydroxide concentration on drying time is the same for the gel of this example as for a gel of the present invention. Example 3 :

[0312] In this example, we study the influence of the super-absorbent polymer on the effectiveness of biological decontamination of a mortar expressed by the number of Bacillus thuringiensis spores on a mortar sample. Experimental protocol :

[0313] Mortar samples are contaminated by depositing a drop of water with a volume of 100 µl containing 2x10 7< spores of Bacillus thuringiensis.

[0314] After diffusion of the contaminating solution into the depth of the cementitious material, the decontamination biocidal gels are spread on the contaminated face of the mortar samples. The quantity of gel deposited is equal to 1000 g / m 2 < .

[0315] After 24 hours of drying, the dry gel flakes formed are removed from the mortar sample. The latter is then immersed in a Luria Broth nutrient solution kept stirring for 3 hours at a temperature of 37°C.

[0316] The revelation of the residual biological activity of the mortar samples then consists of taking a known volume of Luria Broth nutrient solution in which the mortar samples have been soaked and placing it on an agarose gel. After 24 hours of incubation, the counting of the bacterial colonies reveals the number of spores not inactivated by the decontamination biocide gel.

[0317] The gel comprising a super-absorbent polymer has the following composition in mass percentages: Alumina: 14% Sodium hydroxide solution (1M): 85% Surfactant (Pluronic ®< P8020): 0.7% Super-absorbent polymer: Sodium polyacrylate Norsocryl ®< S35: 0.3%

[0318] The gel without absorbent polymer has the same composition except that the superabsorbent polymer is omitted.

[0319] The graph of the Figure 9 shows that the addition of super-absorbent polymer can significantly increase the effectiveness of decontamination of a porous material such as mortar which is deeply contaminated to a thickness of several millimeters.

[0320] This example is not carried out with a gel conforming in all respects to the gel according to the invention, however the results of this example can also be applied to a gel according to the invention.

[0321] The effect of adding a superabsorbent polymer on the effectiveness of biological decontamination is the same for the gel of this example as for a gel of the present invention. Example 4 :

[0322] In this example, we study the influence of the surfactant concentration, namely Pluronic ®< P 8020, on the adhesion power of dry gel flakes.

[0323] The gel studied is a gel which has the following composition in mass percentages: Alumina: 14%; Sodium hydroxide solution (1M): 85%; in which the concentration of surfactant (Pluronic) is varied ® P8020).

[0324] The other compounds being maintained at equal mass contents.

[0325] The surfactant concentrations are 0 g / L; 10 g / L; and 50 g / L. Experimental protocol :

[0326] The gel is applied to a flexible stainless steel blade (calibrated sheet from Outillage francilien), whose mechanical properties are known (25 µm thick, 2 cm long, 1 cm wide and a Young's modulus of 2.10 11< Pa), one end is fixed and the other free. The surface of the gel layer is leveled with a suitable scraper in order to deposit a constant thickness of one mm.

[0327] Two cameras are added, one camera placed above the gel layer allows the appearance of fractures to be visualized and another placed on the side allows the evolution of the thickness of the gel layer over time to be measured. The adhesion of the flakes is studied by analyzing the images obtained by the two cameras.

[0328] The graph of the Figure 10shows that in the concentration range of interest to us (< 10 g / l), increasing the concentration of Pluronic ®< results in a reduction in the adhesion of the flakes. The recovery of dry gel waste by brushing and / or suction is then made easier.

[0329] This example is not carried out with a gel conforming in all respects to the gel according to the invention, however the results of this example can also be applied to a gel according to the invention.

[0330] The effect of surfactant concentration on the adhesive power of dry gel flakes is the same for the gel of this example as for a gel of the present invention. Example 5 :

[0331] In this example, we study the influence of the surfactant concentration, namely Pluronic ®< P 8020, on the number of dry gel flakes formed.

[0332] The gel studied is the gel of example 4 in which the surfactant concentration is varied.

[0333] The surfactant concentrations are 0 g / L; 10 g / L; and 50 g / L.

[0334] The experimental protocol used is strictly the same as that used in example 4.

[0335] The graph of the Figure 11 shows that the addition of Pluronic ®< to the gel formulation results in a reduction in the number of flakes. The addition of Pluronic ®< improves the toughness of the gel matrix against fracturing induced by drying: the gel will fracture more difficultly, the number of fractures will be lower and the number of flakes will therefore be smaller. Regarding the decontamination process, the reduction in the number of flakes is beneficial: the flakes being larger, the waste will be non-powdery during the waste recovery phase by brushing and / or suction.

[0336] This example is not carried out with a gel conforming in all respects to the gel according to the invention, however the results of this example can also be applied to a gel according to the invention.

[0337] The effect of surfactant concentration on the number of dry gel flakes formed is the same for the gel of this example as for a gel of the present invention. Example 6.

[0338] In this example, we study the evolution of the viscosity of gels as a function of temperature.

[0339] The two gels studied have the following compositions in mass percentages: First frost : Silica: 9%. H2O: 91%. Second gel: 1-Carrageenan: 0.6% H 2 O: 99.4%.

[0340] The results of this study are reported on the Figure 12 .

[0341] This example shows that silica-type mineral particles act as a viscosifier to allow the solution to gel and thus adhere to surfaces and that the viscosity of the gel containing carrageenan decreases with temperature. Example 7.

[0342] In this example, we study the influence of silica on the morphology of gels after drying.

[0343] The two gels studied have the following compositions in mass percentages: First frost : t-Carrageenan: 1.2% H 2 O: 98.8% Second frost : 1-Carrageenan: 1.2% Silica: 9% H 2 O: 89.8% Experimental protocol.

[0344] The gels are deposited on a stainless steel sample 4 cm on each side and hollowed out to a depth equal to 1 mm.

[0345] The objective here is to perfectly control the thickness of the deposited gel. From then on, the gels are subjected to a drying phase at room temperature (22°C) until the evolution of the mass of the gels no longer evolves.

[0346] The photographs of the Figures 13A and B show that silica-type mineral particles ensure the fracturing of the gel during drying to result in dry waste in the form of flakes (13B), which is not the case for the gel which does not contain silica (13A). Example 8.

[0347] In this example, the surface of a black steel plate is treated with a coating gel according to the invention and the plate thus treated is then observed.

[0348] The gel studied is a gel which has the following composition in mass percentages: Saturated aqueous sodium hydrogen oxalate solution: 98.6% -κ- Carrageenan: 1.4% Experimental protocol.

[0349] The experiment consists of placing a drop of gel, previously heated to a temperature of 50°C, on a black steel plate. The gel, thus in liquid form, is placed on the plate using a Pasteur pipette and then left to dry at room temperature (22°C). Once dry, the gel is recovered by brushing the glitter. The erosion of the plate is then characterized by taking photographs of the plate.

[0350] The photographs of the Figure 14 (A and B) show that erosion was actually generated on the black steel plate by the coating gel. Example 9.

[0351] In this example, part of the surface of a black steel plate is treated with a coating gel according to the invention, while another part of this surface does not undergo treatment.

[0352] The gel studied is a gel which has the following composition in mass percentages: Saturated aqueous sodium hydrogen oxalate solution: 98.6% -κ- Carrageenan: 1.4% Experimental protocol.

[0353] The experiment consists of placing a drop of gel, previously heated to a temperature of 50°C, on a black steel plate. The gel, thus in liquid form, is placed on the plate using a Pasteur pipette and then left to dry at room temperature (22°C). Once dry, the gel is recovered by brushing the flakes. The erosion of the plate is then characterized by optical profilometry.

[0354] Measurements are then taken using an optical profilometer on the part of the surface treated by the gel and on the part of the surface not treated by the gel (see Figure 15 ).

[0355] These measurements show that the surface treated by the gel has indeed undergone erosion to a depth of up to 60 to 70 µm. Example 10:

[0356] Decontamination tests using a "topping gel" type formulation were carried out. These experiments aim to demonstrate the effectiveness of such a gel in a "real" situation, i.e. on a typical material contaminated by radioelements.

[0357] The material to be decontaminated was prepared as follows: a quantity corresponding to approximately 5000 Bq of 60< Co, y emitter, was deposited by "daisy chain deposition" on black steel plates (approximately 1.5 x 1.5 cm). These plates (plates 1 and 2) were then dried in an epiradiator (infrared drying). The activity of the plates was finally measured by gamma counting (results given below in the table).

[0358] In parallel, a "topping gel" was prepared. This is a formulation containing 8% silica (Tixosil 331) mixed with a solution of saturated oxalic acid and sodium hydroxide (in equimolar proportions), to which 1.4g / 100 mL of κ-carrageenan are added while hot.

[0359] The main characteristic of the material obtained is a significant variation in its viscosity depending on the temperature, allowing the coating process.

[0360] The gel, solid at low temperature, was melted and applied to the parts to be decontaminated. After a few hours of drying, the dry residues formed were removed and the residual contamination was measured in the same way as before by gamma counting of the plates.

[0361] Here are the results obtained on two black steel plates (+ / - 5%): Plate 1 Plate 2 Initial deposit 60< Co 5307 Bq 5600 Bq 60< Co after decontamination of the gel 320 Bq 325 Bq That's a decontamination factor of about 17.

[0362] For these tests, the decontamination effectiveness of a coating gel using oxalic acid on black steel contaminated by a 60< Co deposit was therefore demonstrated.

[0363] This example is not carried out with a gel conforming in all respects to the gel according to the invention, however the results of this example can also be applied to a gel according to the invention. REFERENCES

[0364] [1] JENEVEIN. E, “Cleaning composition for neutralizing biological and chemical weapons removal agents”, US-B2-7,026,274. [2] SCHILLING. A, HODGE. R, “Peracid-based large area decontamination”, US-A1-2006 / 0073067. [3] CONERLY. L, EHNTHOLT. D, LOUIE. A, WHELAN. R, “Chemical and / or biological decontamination system”, US-A1-2003 / 0109017. [4] TUCKER. M, COMSTOCK. R, “Decontamination formulation with sorbent additive”, US-A1-2004 / 0022867. [5] ROGERS. JV, SABOURIN. CLK, CHOI. YW, "Decontamination assessment of bacillus subtilis, and Geobacillus stearothermophilus spores on indoor surfaces using a hydrogen peroxide gas generator", 2005 .[6] JOSSE. D, BOUDRY. I, NAUD. N, "Skin decontamination against organophosphorus agents and sulfur mustard gas: Assessment and perspectives", Médecine et armées, vol. 34, n°1, pages 33-36, 2006. [7] HOFFMAN. D, Mc GUIRE. R, "Oxidizer gels for detoxification of chemical and biological agents", US-B1-6,455,751. [8] HARPER. B, LARSEN. L, "A comparison of decontamination technologies for biological agents on selected commercial surface materials", Biological weapons improved response program, April 2001. [9] FAURE. S, FOURNEL. B, FUENTES. P, LALLOT. Y., "Process for treating a surface with a treatment gel, and treatment gel", FR-A1-2 827 530.

[10] FAURE. S, FUENTES. P, LALLOT. Y., "Aspirable gel for decontaminating surfaces and use", FR-A1-2 891470.

[13] YURII. A., "Sol-gel-derived biomaterials of silica and carrageenans", Journal of Colloid and Interface Science, 268 (2003) 68-76, 2003.

[14] FISHERIES AND AQUACULTURE DEPARTMENT."Training Manual on Gracilaria Culture and Seaweed Processing in China", Food and Agriculture Organization of the United Nations, 1990.

[15] BELLAN. C., "Etude et utilisation de matériaux adaptatifs dans le contrôle actif de vibrations", Thèse de l'Université de Nice Sophia-Antipolis, UFR Sciences, 2001.

[16] SUNG. T. L, MIN. S. C., "Magnetorheological characterization of carbonyl iron based suspension stabilized by fumed silica", Journal of Magnetism and magnetic Materials, 282, 170-173, 2004.

[17] KROELL. M, PRIDOEHL. M, ZIMMERMANN. G., "Magnetic and Rheological characterization of novel ferrofluids", Journal of Magnetism and magnetic Materials, 289, 21-24, 2005.

[18] SANG. H, THURSTON. H., "Synthesis and characterization of monodisperse silica colloids loaded with superparamagnetic iron oxide nanoparticles", Chemical Physics Letters, 401, 19-23, 2005.

[19] KUANG. G, JI. Y, JIA. X., "Photoresponsive organogels: an amino acid-based Dendron functionalized with p-nitrocinnamate", Tetrahedron, 65, 3496-3501, 2009.

[20] PIEPENBROCK. M, LLOYD. G, CLARKE. N, STEED. J., "Metal and Anion Binding Supramolecular Gels", Chem. Rev. ACS, 2009.

[21] WENG. W, BECK. B, JAMIESON. A., "Understanding the Mechanism of Gelation and Stimuli-Responsive Nature of Metallo-Supramolecular Gels", J. Am. Chem. Soc, 128, 11663-11672, 2006.

Claims

1. Decontamination gel, consisting of a colloidal solution comprising or consisting of: - 0.1% to 30% by mass, preferably 0.1% to 25% by mass, preferably again 5% to 25% by mass, better 8% to 20% by mass, relative to the mass of the gel, of at least one inorganic viscosifying agent; - 0.01% to 5% by mass, preferably 0.05% to 3% by mass, relative to the mass of the gel, of at least one viscosity variation agent which, when subjected to at least one stimulus, preferably external to the gel, causes a variation in the viscosity of the gel, said stimulus, preferably external to the gel, being selected from chemical stimuli such as a variation in the oxidation-reduction potential of the gel; thermal stimuli such as a variation in the temperature of the gel; physical stimuli such as exposure to an electromagnetic wave; and combinations of two or more of said stimuli, said viscosity variation agent being not a superabsorbent polymer, said viscosity variation agent being selected from the group consisting of polysaccharides, oxidizing compounds, magnetic particles, and compounds the viscosity of which varies when exposed to electromagnetic radiation of different wavelengths; - 0.1 to 10 mol / L of gel, preferably 0.5 to 10 mol / L of gel, preferably again 1 to 10 mol / L of gel, of at least one decontamination active agent different from said viscosity variation agent; - 0.1% to 2% by mass relative to the mass of the gel, of at least one surfactant and preferably of at least one non-ionic surfactant; - optionally 0.05% to 5% by mass, preferably 0.05% to 2% by mass relative to the mass of the gel, of at least one super-absorbent polymer; - and the rest of solvent.

2. Decontamination gel according to claim 1, wherein the inorganic viscosifying agent is selected from aluminas, silicas, aluminosilicates, clays, and mixtures thereof; preferably the inorganic viscosifying agent is selected from pyrogenic silicas, precipitated silicas, hydrophilic silicas, hydrophobic silicas, acidic silicas, basic silicas, and mixtures thereof; preferably again, the inorganic viscosifying agent consists of a mixture of precipitated silica and pyrogenic silica.

3. Decontamination gel according to claim 2, wherein the inorganic viscosifying agent consists of one or more alumina(s) representing from 5% to 30% by mass, preferably from 8% to 17% by mass relative to the mass of the gel.

4. Decontamination gel according to claim 1, wherein the viscosity variation agent is selected from carrageenans.

5. Decontamination gel according to any one of the preceding claims, wherein the decontamination active agent is selected from bases such as sodium hydroxide, potassium hydroxide, and mixtures thereof; acids such as nitric acid, phosphoric acid, hydrochloric acid, sulfuric acid, hydrogen oxalates such as sodium hydrogen oxalate, and mixtures thereof; oxidizing agents such as peroxides, permanganates, persulfates, ozone, hypochlorites, cerium(IV) salts, and mixtures thereof; quaternary ammonium salts such as hexacetylpyridinium salts such as hexacetylpyridinium chloride; reducing agents; and mixtures thereof; the superabsorbent polymer is selected from sodium poly(meth)acrylates, starches grafted with a (meth)acrylic polymer, hydrolyzed starches grafted with a (meth)acrylic polymer; starch, gum, and cellulose derivative based polymers; and mixtures thereof; the nonionic surfactant is selected from block copolymers, sequenced as ethylene oxide and propylene oxide sequenced copolymers, and ethoxylated fatty acids; and mixtures thereof; and the solvent is selected from water, organic solvents, and mixtures thereof.

6. Method for decontaminating at least one surface of a part made of a solid material, said surface being contaminated by at least one contaminant species located on said surface and optionnaly under said surface in the depth of the part, wherein at least one cycle is carried out comprising the following successive steps: a) the part is immersed in a bath of the according to any one of claims 1 to 5, in the liquid state with a viscosity of less than 0.1 Pa.s; b) the part, coated with a film of the gel, is removed from the bath and immediately subjected to at least one stimulus that causes an increase in the viscosity of the gel in a time of less than 5 seconds and its transition to a gelled state with a viscosity greater than 100 Pa.s; c) the gel is maintained on the contaminated surface for at least a sufficient time for the gel to destroy and / or inactivate and / or absorb the contaminant species, and for the gel to dry and form a dry solid residue containing said contaminant species; d) the dry solid residue containing said contaminant species is removed.

7. Method according to claim 6, wherein said stimulus is selected from chemical stimuli such as a variation in the oxidation-reduction potential of the gel; thermal stimuli such as a variation in the temperature of the gel; physical stimuli such as exposure to an electromagnetic wave; and combinations of two or more of said stimuli; preferably said stimulus is a decrease in temperature, caused for example by the passage of the part from a heated bath, for example at a temperature of 30°C to 80°C, to the ambient atmosphere, for example at a temperature of 15°C to 25°C; or said stimulus is either the beginning of the exposure of the gel to a magnetic field or the stopping of the exposure of the gel to a magnetic field.

8. Method according to claim 6 or 7, wherein the increase in viscosity of the gel during step b) occurs in a time of less than 2 seconds, preferably less than or equal to 1 second, for example in a time of between 0.5 second and 1 second.

9. Method according to any one of claims 6 to 8, wherein the part is a part of small size and / or complex shape.

10. Method according to any one of claims 6 to 9, wherein the solid material is selected from metals and metal alloys such as stainless steel, aluminum and lead; polymers such as plastics or rubbers such as polyvinyl chloride or PVC, polypropylenes or PP, polyethylenes or PE especially high density polyethylenes or HDPE, polymethyl methacrylates or PMMA, poly(vinylidene fluoride) or PVDF, polycarbonates or PC; glasses; cements and cementitious materials; mortars and concretes; plaster; bricks; natural or artificial stone; ceramics.

11. Method according to any one of claims 6 to 10, wherein the contaminant species is selected from chemical, biological, nuclear or radioactive contaminant species, for example the contaminant species is a biological species chosen from bacteria, fungi, yeasts, viruses, toxins, spores and protozoa, in particular the biological species is selected from among biotoxic species such as pathogenic spores such as for example Bacillus anthracis spores, toxins such as for example botulinum toxin, and viruses.

12. Method according to any one of claims 6 to 11, wherein the gel is applied to the surface at a rate of 100 g to 2000 g of gel per m2 of surface, preferably from 500 g to 1500 g of gel per m2, preferably again from 600 g to 1000 g of gel per m2 of surface.

13. Method according to any one of claims 6 to 12, wherein, during step c), the drying is performed at a temperature of 1°C to 50°C, preferably from 15°C to 25°C, and at a relative humidity of 20% to 80%, preferably from 20% to 70%.

14. Method according to any one of claims 6 to 13, wherein the gel is held on the surface for a period of 2 to 72 hours, preferably 2 to 48 hours, preferably still 5 to 24 hours.

15. Method according to any one of claims 6 to 14, wherein the dry solid residue is in the form of particles, for example flakes, of a size from 1 to 10 mm, preferably from 2 to 5 mm.

16. Method according to any one of claims 6 to 15, wherein the dry solid residue is removed from the solid surface by brushing and / or vacuuming.

17. Method according to any one of claims 6 to 16, wherein the described cycle is repeated 1 to 10 times using the same gel during all cycles or using different gels during one or more cycle(s).

18. Method according to any one of claims 6 to 17, wherein, during step c), the gel, before complete drying, is soaked with a solution of a decontamination agent, preferably with a solution of the active decontamination agent of the gel of the bath of step a) in the solvent of this gel.