Absorbent gel and method for disposing of a contaminant contained in an organic layer on a surface of a substrate

Description

TECHNICAL FIELD

[0001] The present invention relates to a gel for eliminating contamination, for example radioactive contamination, contained in an organic layer on the surface of a solid substrate.

[0002] More precisely, by organic layer we mean a layer made of an organic material, consisting of an organic material.

[0003] In this text, the terms contamination, for example radioactive contamination, contaminant, for example radioactive contaminant, or contaminating species, for example radioactive contaminating species, are used interchangeably.

[0004] The contaminating species that can be eliminated by the gel according to the invention can include radioactive and / or chemically toxic contaminating species, and / or toxic species due to their shape and / or size such as dust, microparticles, nanoparticles, or fibers.

[0005] In particular, the gel according to the invention can be used to remove asbestos contained in an organic layer on the surface of a solid substrate.

[0006] The present invention also relates to a method for eliminating contamination, for example radioactive contamination, contained in an organic layer on the surface of a solid substrate.

[0007] This organic layer can be a contaminated surface organic layer of a solid substrate made up of organic material.

[0008] More specifically, in this case, the contaminated surface organic layer is an integral part of the solid substrate, and the organic layer and the solid substrate are made of the same organic material.

[0009] This solid substrate made of an organic material can be a bulk substrate or a layer, such as a layer of paint or epoxy resin, for example a layer of paint or epoxy resin forming a coating on a surface of (another) solid substrate.

[0010] Alternatively, this organic layer may be a layer consisting of contaminated organic material, found on a surface of a solid substrate, this layer appearing in particular in the form of a spot or discrete spots of contaminated organic material soiling said surface, for example a contaminated oil or bitumen stain soiling said surface.

[0011] In this case, the contaminated surface layer and the solid substrate are not made of the same organic material and the solid substrate can be made of any material: metal, resin, paint etc.

[0012] The technical field of the invention can be defined, in general terms, as that of decontamination, for example radioactive decontamination of surfaces, with a view to eliminating from these surfaces contamination, for example radioactive decontamination, namely contaminating species, for example radioactive contaminating species.

[0013] The invention applies, in particular, to the decontamination of contaminated surfaces in the context of the dismantling and remediation of nuclear installations, or in the context of asbestos removal from buildings. PREVIOUS STATE OF THE ART

[0014] As part of the cleanup and dismantling operations of nuclear facilities, various decontamination steps are necessary.

[0015] The diversity of materials present in nuclear facilities, as well as the surface condition of these materials, makes decontamination operations difficult and requires adapting treatment processes to the materials and the targeted contamination.

[0016] In particular, one of the most important problems that arises is the decontamination of contaminated organic matrices composed of contaminated organic materials, such as paints or epoxy resins, or the decontamination of surfaces soiled by traces of contaminated organic matrices, such as contaminated bitumen or oil stains that are often present on nuclear installation sites.

[0017] Difficulties are encountered mainly when the contamination is embedded within the organic matrix.

[0018] The decontamination processes used today for the decontamination of organic matrices such as wall paints or epoxy resins rely in particular on classic surface cleaning techniques using wipes - used dry or impregnated with decontaminating and / or degreasing solutions - or wiping, which are carried out manually in often very sensitive nuclear environments.

[0019] Numerous rudimentary mechanical decontamination methods are also used. These methods employ techniques such as cutting, sanding, or stripping. These techniques are tedious and laborious to implement, generate dust, and are often ineffective on relatively thick organic layers.

[0020] These mechanical decontamination processes are being optimized and are now often coupled with thermal processes using, for example, lasers or thermal lances.

[0021] These optimized mechanical processes, however, remain relatively demanding in terms of the physical strain of the work. Furthermore, the addition of a thermal process can significantly increase the implementation cost.

[0022] Other decontamination processes use aqueous or organic chemical solvents. These processes can also decontaminate contaminated organic matrices by applying the solvents directly to the surfaces of these matrices.

[0023] These decontamination processes which use chemical solvents are however rarely used on decontamination sites, due to the significant production of contaminated effluents.

[0024] Regarding the removal of traces of contaminated organic matrices, such as oil or bitumen stains that soil the surfaces of nuclear facilities, there are still no adequate decontamination processes, especially since these traces of organic matrices are generally sticky and adhere to the surface on which they are found. This is particularly true of contaminated bitumen stains.

[0025] While vacuum systems exist that can collect loose dust from a surface, these systems are not suitable for sticky deposits. Furthermore, after these vacuum systems are installed, a floor scrubber is typically used, but this generates a significant amount of wastewater.

[0026] Finally, for heavily adherent stains, human intervention is necessary with tedious and time-consuming operations of washing using wipes or scraping.

[0027] Among the prior art documents that describe the use of an organic solvent, we can cite document FR-A1-2 957 929 [5].

[0028] This document concerns a process for treating a solid surface, specifically an anti-fouling treatment process suitable for the curative and / or preventive treatment of a solid surface. This process is intended, in particular, for the removal and / or prevention of graffiti and tags.

[0029] According to this process, a composition comprising at least one ester of a carboxylic acid, which is an ester of an odd acid, is applied to the surface. This composition may be in the form of a microemulsion.

[0030] There is no mention, nor any suggestion, that this composition could be in the form of a gel.

[0031] Among the prior art documents that describe the use of an organic solvent, in the form of a gel, we can cite document WO-A1-99 / 09134 [3].

[0032] This document relates to a cleaning composition for removing long-chain compounds such as bitumen, tar, wax and chewing gum which comprises an inert gel matrix within which is enclosed a non-aqueous liquid solvent in which the long-chain compound is soluble.

[0033] The gel matrix is ​​formed, for example, by silica or clay, but not by alumina.

[0034] The solvent can be chosen from saturated and unsaturated hydrocarbons, alcohols, glycols, aldehydes, ketones, ethers, terpenes, phthalates, esters, or halogenated hydrocarbons.

[0035] The freezing of this document is not a freeze that can be described as a vacuumable freeze.

[0036] Furthermore, this document contains no description of the process used to apply or implement the gel.

[0037] The only example given in this document concerns the removal of chewing gum, the composition of which is very different from that of contaminated surface layers, which are generally made up of epoxy resin or paint, and from that of stains of contaminated organic material, which are generally made up of contaminated oil or bitumen.

[0038] In addition, long-chain compounds, for example chewing gum, eliminated in this document are not contaminated by contaminating species, for example by radioactive contaminating species, and therefore do not contain such species.

[0039] Finally, there is no mention or suggestion in this document that the gel described therein can be used to solve the specific problem of removing contamination, such as radioactive contamination, contained in a layer of organic material.

[0040] Furthermore, in the context of nuclear decontamination, gel formulations which make it possible to overcome the problems related to the powdery nature of dry waste, and to increase the efficiency of the process using a gel, have been the subject of documents FR-A1-2 827 530 [1] and FR-A1-2 891470 [2].

[0041] These documents describe inorganic colloidal gels called "aspirable gels", specifically formulated to be sprayed, then to dry by fracturing, while trapping and confining radioactive contamination in the form of non-powdery, aspirable flakes, which can be directly packaged and stored.

[0042] Document [1] describes a gel consisting of a colloidal solution comprising an inorganic thickening agent, usually silica or alumina, an active processing agent which is for example an inorganic acid or base such as sodium hydroxide or potassium hydroxide, and possibly an oxidizing agent having a normal redox potential E 0 greater than 1.4 V in a strong acidic medium such as Ce(IV), Co(III), or Ag(II).

[0043] Document [2] describes a gel consisting of a colloidal solution comprising an inorganic thickening agent, usually silica or alumina, a surfactant, an inorganic acid or base, possibly an oxidizing agent having a normal redox potential E 0 greater than 1.4 V in a strong acidic medium such as Ce(IV), Co(III), or Ag(II).

[0044] These inorganic colloidal gels, due to the different constituents in their composition, have a rheology that allows them to be sprayed onto a contaminated surface, and then to adhere to that surface, even vertical, without running.

[0045] This allows prolonged contact between the contaminant and the active decontamination agent, without altering the mechanical properties of the substrate.

[0046] Following its spraying, the gel dries, fractures, and produces dry residues, called "flakes", which adhere to the substrate and are subsequently removed by brushing or vacuuming to be directly packaged.

[0047] Decontamination processes using these aspirable gels are therefore dry decontamination processes, generating no liquid effluent and very little dry solid residue. In fact, this dry solid residue represents on average only a quarter of the initial gel mass. Furthermore, these processes limit the operator's exposure time to radioactive contamination, due to their ease of implementation through spraying followed by aspiration of the dry residue, and because the operator's presence is not required during the gel drying process.

[0048] The gels described in documents [1] and [2] are, however, specifically intended for the removal of radioactive contamination located on the surface of a substrate, whether organic or otherwise. This radioactive contamination is not contained within a layer of organic material.

[0049] The gels in these documents are in no way specifically adapted for the removal of contamination, for example radioactive contamination, contained in a layer of organic material, or even likely to be adapted for the removal of contamination, for example radioactive contamination, contained in a layer of organic material.

[0050] There is no mention or suggestion in documents [1] and [2] that the gels in these documents could solve the extremely specific problem of removing contamination, for example radioactive contamination, contained in a layer of organic material, embedded in an organic matrix, which is a completely different problem from the problem of removing contamination, for example radioactive contamination, on the surface.

[0051] The inventors highlighted that the aspirable gels described in documents [1] and [2], although used for some years in the field of nuclear surface decontamination, on surfaces made of materials such as steels, such as stainless steel, aluminum or lead, were not at all effective when it came to eliminating contamination, for example radioactive contamination, contained in a layer of an organic material, integrated into an organic matrix, in other words when it came to decontaminating organic matrices such as wall paints or bitumen stains.

[0052] Documents FR-A1-2962046 and WO-A1-2012 / 001046 [6] relate to a "suctionable" biological decontamination gel and a biological decontamination process for surfaces using this gel.

[0053] This gel consists of a colloidal solution comprising at least one inorganic thickening agent, at least one biological decontamination agent, at least one super-absorbent polymer, at least one surfactant, and the remainder solvent.

[0054] Documents FR-A1-3003763 and WO-A1-2014 / 154818 [7] relate to an aspirable oxidizing alkaline biological decontamination gel and a biological decontamination process for surfaces using this gel.

[0055] This gel consists of a colloidal solution comprising at least one inorganic thickening agent, a biological decontamination agent consisting of a combination of a specific mineral base, such as sodium hydroxide, and a specific oxidizing agent stable in a basic medium, such as sodium hypochlorite, optionally a surfactant, and the remainder solvent. Furthermore, this gel does not contain a superabsorbent polymer.

[0056] The gels described in documents [6] and [7] are specifically designed for the biological decontamination of surfaces, particularly for post-event surface decontamination. This biological contamination is found on the surface of a substrate, whether organic or otherwise. This biological contamination is not contained within a layer of organic material.

[0057] The gels in these documents are in no way specifically adapted for the removal of contamination, such as radioactive contamination, contained in a layer of organic material, or even likely to be adapted for the removal of contamination, such as radioactive contamination, contained in a layer of organic material.

[0058] There is no mention or suggestion in documents [6] and [7] that the gels in these documents could solve the extremely specific problem of removing contamination, such as radioactive contamination, contained in a layer of organic material, embedded in an organic matrix, which is a completely different problem from the problem of removing biological contamination on the surface.

[0059] Document FR-A1-3 027 310 [4] relates to a vacuumable gel for removing graffiti and a process for removing graffiti.

[0060] This gel consists of a colloidal solution comprising an organic thickening agent, one or more organic solvents chosen in particular from alkyl acetates, possibly a surfactant, and possibly at least one colorant and / or pigment.

[0061] The gel described in document [4] is, however, specifically intended for the removal of graffiti that does not contain any contamination, for example, no radioactive contamination.

[0062] Freezing this document is in no way suitable for the removal of contamination, for example radioactive contamination, contained in a layer of organic material, or even likely to be suitable for the removal of contamination, such as radioactive contamination, contained in a layer of organic material.

[0063] There is no mention or suggestion in document [4] that freezing this document could solve the extremely specific problem of removing contamination, such as radioactive contamination, contained in a layer of organic material embedded in an organic matrix, which is a completely different problem from the problem of removing graffiti.

[0064] Therefore, in view of the above, there is a need for aspirable gel and a process for removing contamination, for example radioactive contamination, contained in a surface layer of an organic material, integrated into an organic matrix.

[0065] In other words, there is a need for aspirable gel formulations that can decontaminate surfaces made of organic matter, for example surfaces made of paint or epoxy resin, or surfaces soiled by contaminated organic matter, such as bitumen or oil stains that can be found in particular, but not exclusively, nuclear facilities.

[0066] The aim of the present invention is to provide a suctionable gel that meets, among other things, these needs.

[0067] The object of the present invention is further to provide aspirable gel which does not have the drawbacks, defects and disadvantages of prior art gels and which solves the problems of prior art gels, such as document gels [1] and [2]. DESCRIPTION OF THE INVENTION

[0068] This goal, and others, are achieved, according to the invention, by a suctionable gel for removing a contaminant species, for example a radioactive contaminant species, contained in a layer made of an organic material, on the surface of a solid substrate, consisting of a colloidal solution comprising, preferably, of: 1% to 25% by mass, preferably 5% to 20% by mass, for example 10% by mass, relative to the total mass of the gel, of at least one inorganic thickening agent; 13% to 99% by mass, preferably 80% to 95% by mass, for example 90% by mass, relative to the total mass of the gel, of one or more organic solvent(s) selected from among the terpenes; optionally, 1% to 40% by mass, preferably 10% to 20% by mass relative to the total mass of the gel, of ethanol; optionally, 0.01% to 10% by mass, relative to the total mass of the gel, of at least one colorant and / or pigment; optionally, 0.1% to 2% by mass, relative to the total mass of the gel, of at least one surfactant; optionally, from 0.1% to 10% by mass, preferably from 1% to 5% by mass, relative to the total mass of the gel, of at least one extracting agent of the contaminating species, for example at least one extracting agent of radionuclides, preferably chosen from zeolites and clays.

[0069] The sum of the mass percentages of all the components, constituents of the gel, is obviously 100% by mass.

[0070] The gel according to the invention has never been described in the prior art.

[0071] The term "freeze" is perfectly clear to a person skilled in the art and has a widely accepted meaning.

[0072] However, generally, a gel can be considered to have a viscosity greater than or equal to 0.1 Pa.s.

[0073] The gel according to the invention is first of all fundamentally defined in that it is a so-called "aspirable gel".

[0074] The term "aspirable gel", as mentioned above, is a commonly used term in this field of technology; it has a widely accepted meaning.

[0075] An aspirable gel is inherently different from a gel that is not aspirable.

[0076] The gel according to the invention is further characterized by the fact that it contains one or more specific organic solvent(s) chosen from among terpenes and their mixtures.

[0077] These solvents, chosen from among the terpenes, constitute the active principle of the gel according to the invention. They allow the dissolution of organic materials from the contaminated surface layer.

[0078] Thanks to the intrinsic properties of the specific solvent(s) of the gel according to the invention, which are terpenes, the gel according to the invention makes it possible to: To completely dissolve a contaminated organic matrix, for example in the form of stains, which is then incorporated, along with the contamination, into the final solid waste, namely the gel after drying, which is in the form of vacuumable flakes. To dissolve a contaminated organic surface layer, for example a few microns thick, and allow the incorporation of the dissolved layer and the contaminants present within the gel and therefore into the final solid waste, namely the gel after drying.

[0079] This solvent(s) of the gel according to the invention, chosen from among the terpenes is (are) slightly (or not at all) toxic, harmful.

[0080] In other words, according to the invention, care has been taken to ensure that the solvent(s) of the gel is / are specifically chosen from among the least toxic, and least harmful, or even non-toxic and non-harmful solvents, in order to protect the operators who implement the gel according to the invention.

[0081] This is another characteristic that fundamentally differentiates the gel according to the invention from many prior art gels in which solvents, for example essences, which are toxic or harmful, are used.

[0082] The terpene solvent(s) of the gel according to the invention is (are) furthermore solvents which give off an odor which is not or only slightly nauseating, or unpleasant.

[0083] In other words, great care has been taken to ensure that the solvents for the gel according to the invention are chosen from among the solvents whose odor is the least nauseating, the least unpleasant, or even not at all nauseating or unpleasant.

[0084] In other words, the solvents of the gel according to the invention are chosen from solvents which have a limited or even zero "stench".

[0085] The solvent or mixture of terpene solvent(s) of the gel according to the invention also generally has a volatility compatible with a good drying time of the gel, that is to say a volatility which guarantees a not too high drying speed, and therefore a drying time sufficient to ensure at least partial dissolution of the organic material of the layer, absorption of the contamination, for example a drying time of about 20 hours.

[0086] The presence of ethanol in the gel allows, if desired, the drying time to be reduced, for example to about 5 hours.

[0087] Most of the terpenes mentioned above have low volatility, are not very volatile and therefore, when used alone in the gel according to the invention, allow for a sufficient drying time, for example a drying time of about 20 hours.

[0088] Again, the presence of ethanol in the gel, in combination with one or more terpenes with low volatility, makes it possible, if desired, to reduce the drying time to about 5 hours.

[0089] However, some of the terpenes mentioned above have high volatility, produce gels that dry too quickly, and when used alone in the gel according to the invention, do not allow for a sufficient drying time; this is the case, for example, with ocimene.

[0090] These terpene solvents which have high volatility such as ocimene are therefore generally used in combination, in mixture with another terpene solvent (such as limonene) which has low volatility in order to obtain a sufficient drying time.

[0091] It is precisely the combination of such a high-volatility terpene solvent with another lower-volatility terpene solvent that makes it possible to "slow down" the drying of the gel and achieve a good drying time, a sufficient drying time.

[0092] Similarly, care is generally taken to ensure that the volatility of the solvent or mixture of terpene solvents possibly in combination with ethanol is such that the gel does not dry too slowly and that its drying time is not too long and does not exceed, for example, 8 hours.

[0093] A person skilled in the art can easily identify, among the solvents of the gel according to the invention, chosen from the terpenes mentioned above, the solvents having low volatility, and the solvents having high volatility in order to define a formulation having a drying time that is not too long, and not exceeding, for example, 8 hours.

[0094] Furthermore, those skilled in the art know that ethanol is a solvent with high volatility.

[0095] A preferred gel according to the invention consists of a colloidal solution comprising, preferably consisting of, 35% to 98% by mass, preferably 60% to 85% by mass, for example 70% by mass, relative to the total mass of the gel, of one or more terpene(s) selected from, for example, d-limonene, l-limonene, alpha-pinene or beta-pinene, 1% to 25% by mass, preferably 5% to 20% by mass, for example 10% by mass, relative to the total mass of the gel, of an inorganic thickening agent, preferably selected from aluminas, and 1% to 40% by mass, preferably 10% to 20% by mass, for example 19% to 20% by mass, relative to the total mass of the gel, of ethanol.

[0096] Surprisingly, although the organic solvents of the gel according to the invention, which are terpenes, are chosen from solvents that are not very toxic (or even non-toxic), harmful, these solvents alone or in mixture nevertheless exhibit high efficiency in dissolving the material of the organic layer containing the contamination, for example radioactive contamination, whatever that material may be, for example resin paint or other.

[0097] In other words, the solvent of the gel according to the invention, which is chosen from among the terpenes, is relatively non-toxic and has strong dissolving properties towards organic materials but also degreasing properties.

[0098] Terpenes can be chosen from among terpenic hydrocarbons, oxygenated terpenic compounds, and isomers, including optical isomers, of these.

[0099] The terpene(s) in the gel is / are also chosen according to the nature of the organic material that constitutes the contaminated layer in order to allow the most efficient dissolution of this material.

[0100] Terpenes also include isomers, particularly optical isomers of these.

[0101] Among the terpenes, we can mention in particular ocimene, α-pinene, β-pinene, limonene, menthol, menthone, terpineol, isoborneol, camphor, nerol, citronellal, citronellol, myrcene, myrcenol, linalool, geraniol, and the isomers, in particular the optical isomers of these.

[0102] The gel according to the invention comprises, as an organic solvent selected from among the terpenes, preferably as the only organic solvent selected from among the terpenes, d-limonene.

[0103] Indeed, d-limonene has, among all terpenes, the best solubilization power with respect to organic materials, especially with respect to bitumens.

[0104] A particularly preferred gel according to the invention comprises 35% to 94% by mass, preferably 65% ​​to 83% by mass, more preferably 70% to 80% by mass, for example 67% by mass, relative to the total mass of the gel, of d-limonene, and 1% to 40% by mass, preferably 10% to 20% by mass, for example 19% to 20% by mass, relative to the total mass of the gel, of ethanol which allows the drying time to be adjusted.

[0105] The gel according to the invention meets the needs listed above; in particular, while being aspirable, it allows the elimination of contamination, for example radioactive contamination, contained in a layer of organic material.

[0106] In particular, the gel according to the invention allows the effective decontamination of surfaces composed of organic materials, such as paint or epoxy resin, or of surfaces soiled by contaminated organic materials such as bitumen or oil stains.

[0107] Unlike prior art gels, the gel according to the invention, thanks to the specific solvents it contains, ensures decontamination, for example radiological decontamination, by complete or partial dissolution of the organic material containing the contaminants, for example radioactive contaminants, and the incorporation of the dissolved organic material containing the contaminants, for example radioactive contaminants, within the gel.

[0108] The gel according to the invention has the same effectiveness, whether the treated layer is a contaminated surface layer of a solid substrate made of contaminated organic material, or whether the treated layer is a layer made of contaminated organic material such as a layer forming a coating on a surface of a substrate, or whether the treated layer is a layer made of contaminated organic material, found on a surface of a substrate, this layer being in particular in the form of a stain of contaminated organic material soiling said surface, for example a stain of contaminated oil or bitumen or grease soiling said surface.

[0109] In the latter case, where the treated layer is in the form of a stain of contaminated organic material soiling a surface, the gel according to the invention exhibits excellent efficacy regardless of the material of that surface and regardless of its surface condition, whether smooth, rough, dense, or porous. The examples provided later demonstrate that the gel according to the invention is equally effective at decontaminating a dense epoxy resin surface as it is a porous concrete surface, removing a contaminated bitumen stain from the latter.

[0110] The gel according to the invention allows the migration of contaminants, of the contamination, for example of radioactive contamination, present in the contaminated organic layer into the gel and, consequently, into the final solid waste constituted by the dry gel, in order to decontaminate said organic layer.

[0111] The gel according to the invention, as already indicated above, is a suctionable gel which has all the advantageous properties - mentioned above - inherent in so-called suctionable gels such as the gels of documents [1], [2], [6], [7] and [4] with the fundamental difference however that, with the gel according to the invention, a contamination, such as a radioactive contamination, contained in a surface layer of an organic material is eliminated and the composition of the gel is therefore adapted accordingly.

[0112] As indicated above, the gels of these documents [1], [2], [6], [7], are aqueous gels specifically designed for the removal of radioactive or biological contamination found on the surface of a substrate, and whose solvents and active decontamination agent are totally different from those of the gel according to the invention.

[0113] There is no indication in documents [1], [2], [6], and [7] that would lead a person skilled in the art to modify the gels in these documents in such a substantial way in order to use them to remove contamination, for example radioactive contamination, contained in a surface layer in an organic material.

[0114] Similarly, the gel in document [4] is a gel specifically designed for the removal of graffiti that does not contain contamination, including radioactive contamination, on the surface of a substrate.

[0115] The freezing of the document [4] simply has an action of dissolving the graffiti and not an action of transferring, migrating in the gel, a contamination, for example a radioactive contamination, contained in the gel.

[0116] There is no indication in document [4] which would lead a person skilled in the art to modify the gel of this document in order to use it for contamination, for example radioactive contamination, contained in a surface layer in an organic material.

[0117] The gel according to the invention is a colloidal gel whose active principle allows the total or partial dissolution of the organic material, and whose rheology is adapted to the application, preferably by spraying on the surfaces to be treated.

[0118] One of the advantages of the gel according to the invention is that it can be applied very easily, by spraying.

[0119] The gel according to the invention dries gradually, prolonging the contact time between the stripping / dissolving agent, namely the solvent, and the organic material, for example, paint. It forms flakes that are easily detached from the surface by brushing or vacuuming—hence the name "vacuumable gel"—thus carrying away the contamination, for example, radioactive contamination, and the dissolved organic material. In cases where the layer of organic material is in the form of a stain or discrete stains of contaminated organic material soiling the surface of a solid substrate, for example, in the form of contaminated oil or bitumen stains, this is achieved without altering the solid substrate material.

[0120] The cleaning operator can thus leave the gel to act on the surfaces to be treated while going to treat other surfaces, without having to be physically present during drying, or to laboriously scrub the surface with a solvent.

[0121] In summary, the gels according to the invention therefore meet all the needs mentioned above, and they exhibit all the advantageous properties known of so-called "aspirable" gels.

[0122] In other words, the combination - which can be described as synergistic - of one or more inorganic thickening agent(s) with the specific solvent of the gel according to the invention chosen from among terpenes and their mixtures, makes it possible to obtain a gel possessing excellent rheological properties, as well as excellent properties of dissolution of organic material, absorption, migration of contamination, for example radioactive contamination, in the gel, and drying, the dry gel being in addition easily aspirated.

[0123] The gel according to the invention, although it contains a viscosifying agent generally exclusively inorganic, mineral, without viscosifying agent, organic, can be described as an organic gel.

[0124] Indeed, the organic matter content of the gel according to the invention is high, at least equal to 70% by mass, for example equal to 90% by mass, because it contains at least 70% by mass, for example 90% by mass of organic solvents.

[0125] The gel according to the invention is a colloidal solution, meaning that the gel according to the invention contains inorganic, mineral, solid particles of a viscosifying agent, the primary elementary particles of which generally have a size of 2 to 200 nm. These inorganic, mineral, solid particles act as a viscosifier, enabling the solution to gel and thus adhere to the surface to be treated, regardless of its geometry, shape, size, and the location of the layers to be treated. The gel according to the invention comprises at least one inorganic viscosifying agent consisting of one or more aluminas, selected from among the fumed aluminas.

[0126] Advantageously, the inorganic thickening agent can be chosen from metal oxides such as aluminas, metalloid oxides such as silicas, metal hydroxides, metalloid hydroxides, metal oxyhydroxides, metalloid oxyhydroxides, aluminosilicates, clays such as smectite, and mixtures thereof.

[0127] In particular, the inorganic thickening agent can be chosen from aluminas (Al2O3) and silicas (SiO2).

[0128] The inorganic thickening agent may comprise only one silica or alumina or a mixture of these, namely a mixture of two or more different silicas (SiO2 / SiO2 mixture), a mixture of two or more different aluminas (Al2O3 / Al2O3 mixture), or a mixture of one or more silicas with one or more aluminas (SiO2 / Al2O3 mixture).

[0129] Advantageously, the inorganic thickening agent can be chosen from among pyrogenated silicas, precipitated silicas, hydrophilic silicas, hydrophobic silicas, acidic silicas, basic silicas such as Tixosil ®< 73 silica, marketed by the company Rhodia, and mixtures thereof.

[0130] Among the acidic silicas, we can notably mention the fumed silicas or silica fumes "Cab-O-Sil" ®< M5, H5 or EH5, marketed by the company CABOT, and the fumed silicas marketed by the company EVONIK INDUSTRIES under the name AEROSIL ®< .

[0131] Among these pyrogenated silicas, AEROSIL ®< 380 silica with a specific surface area of ​​380 m 2< / g is preferred, offering maximum viscosifying properties for a minimum mineral charge.

[0132] The silica used can also be precipitated silica, obtained, for example, by wet preparation by mixing a sodium silicate solution with an acid. Preferred precipitated silicas are marketed by EVONIK INDUSTRIES under the names SIPERNAT® 22 LS and FK 310, or by RHODIA under the name TIXOSIL® 331; the latter is a precipitated silica with an average specific surface area between 170 and 200 m² / g.

[0133] A particularly preferred thickening agent is chosen from among the fumed aluminas. Indeed, it has been found that the combination of one or more aluminas with the specific solvent of the gel according to the invention chosen from among terpenes and their mixtures makes it possible to obtain a gel possessing rheological properties, as well as properties of dissolution of the organic material, absorption, migration of contamination, for example radioactive contamination, into the gel, and even better drying, the dry gel being in addition easily aspirated.

[0134] In particular, the rheological properties of the gel are better when the gel includes one or more pyrogenated aluminas as an inorganic thickening agent, rather than silica or clay, as in the gel in document [3].

[0135] Aluminas can be chosen from calcined aluminas, ground calcined aluminas, pyrogenated aluminas, and mixtures thereof.

[0136] Pyrogenized aluminas are particularly preferred because the gel properties mentioned above, and especially the rheological properties, are even better with these pyrogenated aluminas, especially when these pyrogenated aluminas have a fine particle size, namely generally from 10 nm to 100 nm.

[0137] As an example, we can cite the product sold by the company EVONIK INDUSTRIES under the trade name "Aeroxide ®< Alu C" which is fine pyrogenated alumina.

[0138] Advantageously, according to the invention, the inorganic thickening agent consists of one or more alumina(s), generally representing 1% to 25% by mass, and preferably 5% to 25% by mass relative to the total mass of the gel.

[0139] In this case, the alumina(s) is / are preferably still at a concentration of 5% to 20% by mass, better 7% to 15% by mass, for example 10% to 14% 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 24 hours.

[0140] The nature of the mineral viscosifying agent, particularly when it consists 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.

[0141] Indeed, the dry gel is in the form of particles of controlled size, more precisely of millimeter-sized solid 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, especially when the viscosifying agent is made up of one or more alumina(s).

[0142] It should be noted that the size of the particles generally corresponds to their largest dimension.

[0143] 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 a viscosifier, 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.

[0144] A particularly preferred gel according to the invention consists of a colloidal solution comprising, preferably, of: 1% to 25% by mass, preferably 5% to 25% by mass, preferably still 5% to 20% by mass, better 7% to 15% by mass, for example 10% to 14% by mass, relative to the total mass of the gel, of at least one alumina, preferably at least one pyrogenated alumina, preferably still at least one pyrogenated alumina having a fine particle size; 35% to 94% by mass, preferably 65% ​​to 83% by mass, preferably still 70% to 80% by mass, for example 67% by mass relative to the total mass of the gel, of d-limonene; 1% to 40% by mass, preferably 10% to 20% by mass, for example 19% to 20% by mass, relative to the total mass of the gel, of ethanol.

[0145] Again, obviously, the sum of the mass percentages of all the components, constituents of the gel, is 100% by mass.

[0146] Such a gel unexpectedly possesses a particularly advantageous combination of properties, namely excellent efficiency, including excellent solubilization of organic materials, due essentially to d-limonene, and excellent rheological, drying, and dry residue shape properties due to alumina, particularly pyrogenated alumina.

[0147] The addition of ethanol also allows the drying time to be adjusted as desired.

[0148] The gel according to the invention may also optionally contain at least one colorant and / or at least one pigment.

[0149] Advantageously, the pigment is a mineral pigment. See document WO-A1-2014 / 154817 for further details.

[0150] There are no limitations as to the mineral pigment that is incorporated into the decontamination gel according to the invention.

[0151] Generally, the mineral pigment is chosen from among those that are stable in gel.

[0152] By stable pigment, we generally mean that the pigment does not exhibit a stable change in its color over time, when the gel is stored for a minimum period of 6 months.

[0153] There are no limitations on the color of this pigment, which is generally the color it will impart to the gel. This pigment can be black, red, blue, green, yellow, orange, purple, brown, etc., and even white.

[0154] Generally, the gel has the same color as the pigment it contains. However, it is possible for the gel to have a color that differs from the color of the pigment it contains, but this is not desirable.

[0155] The pigment, especially when it is white, is generally different from the inorganic thickening agent.

[0156] Advantageously, the mineral pigment is chosen in such a way that it gives the gel (i.e. the gel in its wet state, before drying) a different color from the color of a surface to be decontaminated on which the gel is applied.

[0157] Advantageously, the mineral pigment is a micronized pigment, and the average particle size of the mineral pigment can be from 0.05 to 5 µm, preferably from 0.1 to 1 µm.

[0158] The fact that the pigment is micronized prevents it from altering the rheology and sprayability of the gel ("sprayability") because the pigment then has the same micrometric size which is generally that of the inorganic viscosifying agent, such as alumina aggregates.

[0159] Advantageously, the mineral pigment is chosen from among metal oxides (metals) and / or metalloid(s), metal hydroxides (metals) and / or metalloid(s), metal oxyhydroxides (metals) and / or metalloid(s), metal ferrocyanides and ferricyanides (metals), metal aluminates (metals), and mixtures thereof.

[0160] Preferably, the mineral pigment is chosen from iron oxides, preferably micronized, and their mixtures.

[0161] Iron oxides can have different colours, for example they can be yellow, red, purple, orange, brown, or black.

[0162] Indeed, iron oxide pigments are known for having good covering power and high resistance to acids and bases.

[0163] For incorporation into a decontamination gel, iron oxides offer the best performance in terms of stability and coloring power. Thus, an iron oxide content of 0.1%, or even 0.01% by mass, is sufficient to strongly color the gel without altering its properties.

[0164] As already mentioned above, the fact that the iron oxide pigment is preferably micronized helps to prevent it from altering the rheology and sprayability of the gel ("sprayability") because the pigment then has a micrometric size, namely a size which is generally that of the inorganic viscosifying agent, such as alumina aggregates.

[0165] Micronized iron oxides are available from Rockwood ®< under the trade name Ferroxide ®<.

[0166] Examples include Ferroxide ®< 212 M, which is a micronized red iron oxide with an average particle size of 0.1 µm, and Ferroxide ®< 228 M, which is a micronized red iron oxide with an average particle size of 0.5 µm.

[0167] In addition to and / or instead of iron oxides, other colored oxides or hydroxides of metals or metalloids may be incorporated into the gel according to the invention, depending on the pH of the gel. Examples include vanadium oxide (V₂O₅), which is orange; manganese oxide (MnO₂), which is black; cobalt oxide, which is blue or green; and rare earth oxides. However, iron oxides are preferred for the reasons stated above.

[0168] Among the oxyhydroxides, we can mention goethite, that is to say iron oxyhydroxide FeOOH, which is very colored.

[0169] As an example of a metal ferrocyanide, we can cite Prussian blue, that is to say ferric ferrocyanide, and as an example of aluminate, we can cite cobalt blue, that is to say cobalt aluminate.

[0170] The incorporation of a mineral pigment into the gel according to the invention allows for better visualization of the wet gel and then the dry residues regardless of the substrate on which the gel is applied.

[0171] The gel may optionally also contain at least one surfactant (namely a single surfactant or a mixture of surfactants), preferably this or these surfactant(s) is / are selected from non-ionic surfactants such as block copolymers, sequenced such as sequenced copolymers of ethylene oxide and propylene oxide, and ethoxylated fatty acids; and mixtures thereof.

[0172] For this type of gel, the surfactants are preferably block copolymers marketed by BASF under the name PLURONIC ®< .

[0173] Pluronics ®< are sequenced copolymers of ethylene oxide and propylene oxide.

[0174] These surfactants influence the rheological properties of the gel, including the thixotropic nature of the product and its recovery time, and prevent the appearance of dripping.

[0175] Surfactants also allow control of the adhesion of the dry waste, and control of the size of the flakes of dry residue to ensure that the waste does not become pulverized.

[0176] The gel may also contain, in addition, from 0.1% to 10% by mass, preferably 1% to 5% by mass, relative to the total mass of the gel, at least one extracting agent of the contaminating species, for example at least one extracting agent of radionuclides, preferably chosen from zeolites and clays.

[0177] This potential extraction agent, such as a zeolite or clay, can be used in cases where the contaminating species is a radionuclide, but this potential extraction agent can also be used in the case of contaminating species other than radionuclides, such as metals, such as toxic metals or heavy metals.

[0178] The invention further relates to a method for removing a contaminating species, for example a radioactive contaminating species, contained in a layer made of an organic material on the surface of a solid substrate, in which at least one cycle is carried out comprising the following successive steps: a) The gel according to the invention, as described above, is applied to said layer made of an organic material; b) The gel is maintained on the layer made of an organic material for at least a sufficient time for the gel to partially or totally dissolve the organic material of the layer made of an organic material, absorb the contaminant species, for example the radioactive contaminant species (so that the contaminant species migrates into the gel), and for the gel to dry and form a dry, solid, non-powdery residue containing the organic material of the layer made of an organic material that has been dissolved, and the contaminant species, for example the radioactive contaminant species; c) The dry, solid residue containing the organic material of the organic layer that has been dissolved, and the contaminant species, for example the radioactive contaminant species, is removed.

[0179] There are no limitations as to the contaminant species that can be eliminated by the process according to the invention, particularly with regard to its form and chemical composition. Thus, the contaminant species that can be eliminated by the process according to the invention can be an organic or inorganic (mineral) species.

[0180] The contaminating species that can be eliminated by the process according to the invention can be a solid or liquid contaminating species.

[0181] The contaminating species that can be eliminated by the process according to the invention may be, in particular, a radioactive contaminating species, and / or a chemically toxic contaminant, and / or a toxic contaminant due to its shape and / or size.

[0182] The toxic contaminant species, due to its shape and / or size, may be a contaminant species in the form of solid particles such as microparticles, or nanoparticles, for example in the form of fibers such as microfibers or nanofibers, in the form of nanotubes, or in the form of crystals such as nanocrystals.

[0183] These fibers can form a type of wool, such as glass wool or rock wool.

[0184] The toxic contaminant species can notably be in the form of dust.

[0185] It should be noted that some dusts of chemically non-toxic compounds, such as cereal or wood dust, are toxic simply because they are in that form of dust.

[0186] The contaminating species can be chosen from among metals and metalloids in metallic, metalloid, or ionic form, preferably from among the so-called "heavy metals", and toxic metals and metalloids in metallic, metalloid, or ionic form; compounds of these metals and metalloids such as organometallic compounds, metal salts, metal oxides, metal carbides, etc.; ceramics; and glasses, for example in the form of glass wool.

[0187] For the purposes of the invention, the term "heavy metals" means all the elements traditionally designated by this name as well as the elements designated by the name trace metals, or TMMs.

[0188] The so-called "heavy metals", and toxic metals and metalloids include antimony, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tellurium, thallium and tin.

[0189] The contaminating species may include asbestos.

[0190] The radioactive contaminating species can be any chemical compound containing a radionuclide, whether in ionic, molecular or particulate form.

[0191] According to a first variant, the layer made up of an organic material containing a contaminating species, for example a radioactive contaminating species, can be a surface layer of a solid substrate made up of said (the same) organic material (as the layer).

[0192] In other words, according to this first variant, the surface layer is an integral part of the substrate.

[0193] This surface layer is usually 1 to 10 µm thick.

[0194] This organic material can be chosen from paints, lacquers, organic polymers, and organic resins such as epoxy resins.

[0195] This solid substrate made of an organic material can be a solid bulk substrate or a layer, such as a layer of paint or epoxy resin, for example a layer of paint or epoxy resin forming a coating on a surface of a substrate.

[0196] Or, according to a second variant, this layer consisting of an organic material containing a contaminating species, for example a radioactive contaminating species, can be a layer consisting of an organic material containing a contaminating species, for example a radioactive contaminating species, located on a surface of a solid substrate, this layer being able to be in the form of a continuous layer, or being able to be in the form of a spot or discrete spots of the organic material containing a contaminating species, for example a radioactive contaminating species.

[0197] In this second variant, the layer, for example the spot or discrete spots, of the organic material containing a contaminating species, for example a radioactive contaminating species is (are) totally dissolved by the gel.

[0198] In this second variant, the organic material (of the layer) can be chosen from among sticky organic materials.

[0199] Sticky organic materials are well known to the person skilled in the art, who has no difficulty in determining among organic materials those that are sticky, that adhere to a surface on which they are found.

[0200] In this context, sticky organic materials are generally defined as materials that cannot be removed from a surface on which they are located by simple suction.

[0201] The organic material can be chosen from among oils such as hydrocarbon oils, bitumens, tars and greases.

[0202] In this second variant, the solid substrate can be a porous substrate, preferably a porous mineral substrate, or a non-porous substrate.

[0203] The effectiveness of the gel and the process according to the invention is equally good in the presence of a non-porous and / or non-mineral surface as in the presence of a porous and / or mineral surface. Regardless of the solid substrate (porous, mineral, or non-mineral), the discrete stain or stains of the organic material containing a contaminant, for example, a radioactive contaminant, are completely dissolved by the gel (see examples).

[0204] Advantageously, in this second variant, the substrate is made of at least one material chosen from among metals and alloys such as stainless steel, galvanized steel, or zinc; painted steels; organic polymers such as plastics or rubbers like 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; cementitious materials such as pastes, cements, mortars and concretes; plasters; bricks; tiles; raw or fired earth; natural or artificial stones; coatings; fiberglass, fiber cements; asphalt; tar; slate; cellulose-based materials such as wood; and ceramics.

[0205] The substrate may or may not be painted.

[0206] Advantageously, the gel is applied to the surface layer at a rate of 100 g to 10000 g, preferably 500 g to 5000 g, preferably still 500 to 1500 g of gel per m² of surface, better 600 to 1000 g of gel per m² of surface, which generally corresponds to a thickness of gel deposited on the surface of 0.1 mm to 1 cm, preferably 0.5 mm to 5 mm.

[0207] Advantageously, the gel is applied to the surface layer by spraying, brushing or using a trowel.

[0208] Advantageously (during step b)), drying is carried out at a temperature of 1°C to 50°C, preferably from 1°C to 40°C, preferably still from 15°C to 25°C, and under a relative humidity of 20% to 80%, preferably from 20% to 70%.

[0209] Advantageously, the gel is maintained on the surface layer for a period of 2 to 72 hours, preferably 4 to 48 hours, preferably still 6 to 24 hours.

[0210] Advantageously, the dry, solid residue is in the form of particles, for example flakes, with a size of 1 to 10 mm, preferably 2 to 5 mm.

[0211] Advantageously, the dry, solid residue is removed from the surface of the solid substrate by brushing and / or vacuuming.

[0212] 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 cycles.

[0213] Advantageously, in step b), before the gel is completely dry, it is re-wetted with a solvent, preferably the same solvent used in the gel applied in step a). This generally avoids having to reapply the gel to the surface, resulting in reagent savings and a limited amount of waste. This re-wetted operation can be repeated, for example, 1 to 10 times.

[0214] The process according to the invention possesses all the advantageous properties inherent in the decontamination gel which it employs and which have already been extensively described above.

[0215] The process according to the invention makes it possible to eliminate contaminating species, for example radioactive contaminating species, contained in a surface layer of an organic material, while being much less arduous and much less costly than the conventional processes previously used for this purpose, namely: processes using high-pressure methods, which are expensive and "technical" (complex), processes using wipes soaked in harmful solvents, the use of which is long and laborious.

[0216] Thus, the gel according to the invention can be sprayed using a simple, commercially available paint gun, whereas sandblasting equipment, for example, requires specific adjustments and training. These sandblasting devices are complex and their maintenance is costly.

[0217] Furthermore, the process according to the invention is a dry process that avoids spills of solvent or stripper while optimizing the cleaning operator's working time. Indeed, the operator is able to treat several areas simultaneously and quickly, thanks to the gel's drying time and its advantageous application by spraying.

[0218] In summary, the process and the gel according to the invention exhibit, among other things, in addition to the advantageous properties specifically due to the specific solvent contained in the gel, the following other advantageous properties: The gel is preferably applied by spraying. Spraying allows for quick and easy treatment of large areas and requires fewer operators, adheres to walls, and achieves maximum efficiency in eliminating contamination after the gel's drying phase, including in the case of contaminated stains penetrating the substrate, particularly in the case of porous surfaces.

[0219] Generally, the drying time is ensured to be greater than or equal to the time required to remove the surface layer or stains. In the case of deep contamination, rewetting is sometimes necessary. the processing of a very wide range of materials (see examples), the absence of mechanical or physical alteration of the materials of the solid substrate at the end of the treatment, the implementation of the process in variable climatic conditions (see examples), the reduction of the volume of waste, the ease of recovery of the dry waste.

[0220] The examples provided later show in particular that the gel according to the invention, due to its specific formulation and its simple, reliable and easy implementation, is effective in particular for the removal of a wide variety of contaminated stains on a wide variety of materials.

[0221] Other features and advantages of the invention will become more apparent from the detailed description that follows, this description being given for illustrative purposes only and not as a limitation, in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0222] There Figure 1(A, B, C, D, E) presents photographs showing the removal of a bitumen stain from a dense, smooth surface, as demonstrated in Example 2, using the gel according to the invention, referred to as gel "Limo-1 » prepared in example 1. The Figure 2 (A, B, C, D, E, F, G) presents photographs showing the removal of a bitumen stain from a porous surface, as demonstrated in Example 2, using the gel according to the invention, referred to as gel "Limo-1 ", prepared in example 1. The Figure 3 (A, B, C) presents photographs showing the removal of a bitumen stain contaminated with 137Cs adhering to a dense, smooth surface, as demonstrated in Example 4, using the gel according to the invention, referred to as gel "Limo-1" prepared in example 1. The Figure 4A Figure 6 illustrates this and presents a photograph of the surface of an epoxy resin before the deposition of a layer of gel according to the invention, referred to as gel. "Limo-1" Prepared in Example 1, on the surface of an epoxy resin (left) and after the application of a gel layer, the drying of this layer, and the removal of the dried gel flakes (right). Figure 4B , illustrates example 6, and shows the surface profiles corresponding to the surfaces photographed on the figure 4A Before applying a layer of epoxy resin to the surface (left) and after applying a layer of gel, allowing this layer to dry and removing the dried gel flakes (right). Figure 5 is a graph that shows the evolution of viscosity (in Pa.s) as a function of shear rate (1 / s), for the gel according to the invention, referred to as gel "Limo-1" prepared in example 1 (see example 7). The Figure 6 is a graph that shows the evolution of the shear stress (in Pa) as a function of the strain (in Pa) for the gel according to the invention, referred to as gel "Limo-1 » prepared in example 1 (see example 7). The Figure 7 is a graph that shows the evolution of the mass loss (in %) as a function of time (in min.) of the gel according to the invention, called gel "Limo-1 Prepared in example 1, deposited with a thickness of 2 mm (see example 8). The Figure 8 is a photograph of the glitter obtained after drying of the gel according to the invention, called gel " Limo-1 » prepared in example 1 (see example 8). The Figure 9 (A, B, C) presents photographs which show the removal of a bitumen stain on a dense, smooth surface, as carried out in Example 9, using the gel according to the invention, called " Limo-2 » prepared in example 9. DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0223] The gel according to the invention can be easily prepared at room temperature.

[0224] For example, the gel according to the invention can be prepared by adding preferably gradually, the inorganic thickening agent(s), for example alumina(s) and / or silica(s), to the terpene solvent(s) possibly mixed with ethanol, or to the mixture of the organic solvent(s) (possibly with ethanol) and the possible adjuvant(s).

[0225] Possible adjuvants are generally the surfactant(s), the colorant(s) and / or pigment(s), and the extracting agent(s) of the contaminating species, for example the extracting agent of radionuclides.

[0226] This mixing of the solvent(s) and any additive(s) can be carried out by mechanical stirring, for example using a mechanical stirrer equipped with a three-bladed propeller. The rotation speed is, for example, 200 rpm, and the stirring time is, for example, 3 to 5 minutes.

[0227] The addition of the inorganic thickening agent(s) to the solvent or solvent(s), or to the mixture of the solvent(s) and any adjuvant(s), can be carried out by simply pouring the thickening agent(s) into said solvent(s) or mixture.

[0228] When adding the inorganic thickening agent(s) to the solvent(s), or to the mixture of the solvent(s) and any adjuvant(s), this solvent(s) or mixture is generally kept under mechanical agitation.

[0229] This agitation can, for example, be achieved by means of a mechanical agitator equipped with a three-bladed propeller.

[0230] The stirring speed is generally increased gradually as the viscosity of the solution increases, eventually reaching a stirring speed of, for example, between 400 and 600 revolutions per minute, without any splashing.

[0231] After the addition of the mineral thickener(s), agitation is continued, for example for 2 to 5 minutes, in order to obtain a perfectly homogeneous gel.

[0232] It is quite clear that other protocols for preparing the gels used according to the invention can be implemented with the addition of the gel components in a different order than that mentioned above.

[0233] Generally, the gel used according to the invention must have a viscosity of less than 200 mPa·s under a shear stress of 1000 s⁻¹ to allow spraying onto the surface to be decontaminated, either from a distance (e.g., 1 to 5 m) or at close range (e.g., less than 1 m, preferably 50 to 80 cm). The viscosity recovery time must generally be less than one second, and the viscosity under low shear must be greater than 10 Pa·s to prevent it from running down a surface.

[0234] It should be noted that the optional surfactant in the gel according to the invention favorably and significantly influences the rheological properties of the gel used according to the invention. In particular, this surfactant allows the gel used according to the invention to be applied by spraying and avoids the risks of spreading or dripping when treating vertical surfaces and ceilings. This surfactant also helps to limit the bleeding phenomenon observed during the gel's storage.

[0235] The gel thus prepared is then applied to the surface layer containing a contaminant species, for example a radioactive contaminant species, to be treated.

[0236] According to the second variant of the method according to the invention, this surface layer containing a contaminating species, for example a radioactive contaminating species, is a layer located on a surface of a solid substrate, this layer being in the form of a spot or discrete spots of the organic material containing a contaminating species, for example a radioactive contaminating species.

[0237] In this second variant, there is virtually no limitation as to the material which constitutes the substrate; indeed, the gel according to the invention allows all kinds of materials, even fragile ones, to be treated without any damage.

[0238] The gel according to the invention does not cause any alteration, erosion, or chemical, mechanical, or physical attack on the treated substrate material. Therefore, the gel according to the invention is in no way detrimental to the integrity of the treated materials and even allows for their reuse. This substrate material can thus be chosen from among the materials already listed above, for example, from metals or alloys such as stainless steel, polymers such as plastics or rubbers, including PVC, PP, PE (particularly HDPE), PMMA, PVDF, and PC, as well as glass, cement, mortar and concrete, plaster, brick, natural or artificial stone, coatings, and ceramics.

[0239] In all cases, regardless of the material that constitutes the substrate, for example stainless steel, painted steel, lacquered steel, glass, ceramic, concrete, PVC, in this second variant, the discrete stain or stains of the organic material containing a contaminant species, for example a radioactive contaminant species, is (are) totally dissolved by the freeze.

[0240] There is also no limitation as to the shape, geometry and size of the layer to be treated and of the solid substrates of the first and second variants, the gel according to the invention allows the treatment of large surfaces, of complex geometries, presenting for example hollows, angles, corners.

[0241] The gel according to the invention ensures the effective treatment not only of horizontal surfaces, but also of vertical surfaces such as walls, facades, bridge piers, doors, or inclined or overhanging surfaces such as ceilings.

[0242] The gel according to the invention also guarantees complete and effective elimination of contamination regardless of the organic material of the contaminated layer and the nature of the contamination.

[0243] Compared to existing techniques that use liquids such as solutions, the invention uses a gel, which is particularly advantageous for treating large, non-transportable materials located outdoors. Indeed, the process according to the invention, due to the use of a gel, allows for cleaning in situ by avoiding the spreading of chemical solutions in the environment and the dispersal of contaminating species.

[0244] The gel according to the invention can be applied to the surface to be treated by all application methods known to a person skilled in the art.

[0245] Conventional methods include spraying, for example with a gun, or application using a brush or a trowel.

[0246] For the application by spraying the gel onto the surface to be treated, the colloidal solution can for example be conveyed by means of a low pressure pump, for example a pump which implements a pressure less than or equal to 7 bars, or about 7.10 5< Pascals.

[0247] The bursting of the gel jet on the surface can be achieved, for example, by means of a flat jet or round jet nozzle.

[0248] The distance between the pump and the nozzle can be any distance, for example it can be from 1 to 50 m, in particular from 1 to 25 m.

[0249] The sufficiently short viscosity recovery time of the gels used according to the invention allows the sprayed gels to adhere to all surfaces, for example to walls.

[0250] The amount of gel deposited on the surface to be treated is as indicated above.

[0251] The amount of gel deposited per unit area and, consequently, the thickness of the gel deposited influences the drying rate.

[0252] Thus, when a film, a layer of gel with a thickness of 0.5 mm to 1 cm is sprayed onto the layer to be treated, the drying time, which is then generally the effective contact time, is sufficient for a good treatment of the layer, leading to a dissolution of the layer and an absorption of the contaminating species.

[0253] The effective contact time is the period during which the active ingredient contained in the gel, which is none other than the solvent(s), will interact with the layer.

[0254] Drying time is not only related to the thickness of the gel layer applied, but also to climatic conditions, namely relative humidity and temperature.

[0255] A person skilled in the art will be able to easily determine, based on climatic conditions and within the thickness range mentioned above, the thickness of the gel layer to be applied to the surface layer so that the gel is effective, the layer is dissolved and the contaminating species are absorbed by the gel.

[0256] Thus, at 20% relative humidity (RH) and 40°C, a 0.5 mm thick layer of gel applied to a surface may dry too quickly to allow for the dissolution of this layer and the absorption of contaminants into the gel. Conversely, at 15°C and 50% RH, the drying of a layer of the same thickness of the same gel allows for the dissolution of this layer and the absorption of contaminants into the gel.

[0257] In addition, it has been shown surprisingly that the amount of gel deposited when it is in the ranges mentioned above and, in particular, when it is greater than 500 g / m 2< and especially in the range of 500 to 5000 g / m 2<, which corresponds to a minimum thickness of gel deposited, for example greater than 500 µm for an amount 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 millimeter flakes, for example of a size of 1 to 10 mm, preferably of 2 to 5 mm aspirable.

[0258] The quantity of gel deposited and therefore the thickness of gel deposited, preferably greater than 500 g / m² or 500 µm, is the fundamental parameter which influences the size of the dry residues formed after drying of the gel and which ensures that dry residues of millimeter size and not powdery residues are formed, such residues being easily removed by a mechanical process and preferably by aspiration.

[0259] However, it should also be noted that when the gel contains a surfactant at a low concentration, the drying of the gel is improved and leads to a homogeneous fracturing phenomenon with a mono-dispersed dry residue size and an increased ability of the dry residue to detach from the support.

[0260] The gel is then kept on the surface to be treated for the entire duration necessary for it to dry.

[0261] During this drying stage, which can be considered the active phase of the process according to the invention, the solvent(s) contained in the gel evaporate(s) until a dry and solid residue is obtained.

[0262] The drying time depends on the composition of the gel within the concentration ranges of its constituents given above, but also, as already mentioned, on the quantity of gel deposited per unit area, i.e., the thickness of gel deposited.

[0263] The drying time also depends on climatic conditions, namely temperature, ventilation and relative humidity of the atmosphere in which the solid surface is located.

[0264] The process according to the invention can be implemented under extremely wide climatic conditions, namely at a temperature T from 1°C to 50°C and at a relative humidity RH from 20% to 80%.

[0265] The drying time of the gel according to the invention is therefore generally from 15 minutes to 24 hours, preferably 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%.

[0266] It should be noted that the formulation of the gel used according to the invention, particularly when it contains surfactants such as "Pluronics ®<", generally ensures (that is to say, generally in reasonable climatic conditions, as indicated above) a drying time which is substantially equivalent to the contact time between the gel and the surface layer which is necessary, required to dissolve the organic material.

[0267] In other words, the gel formulation ensures a drying time that is precisely the time required to dissolve the organic material and absorb the contaminants. Once the gel has dried, it fractures homogeneously, leaving solid, dry residues measuring, for example, 1 to 10 mm, preferably 2 to 5 mm, that are not powdery and generally in the form of solid flakes. These dry, solid residues contain the contaminants, such as radioactive contaminants, and the organic material that has dissolved from the surface layer.

[0268] The dry residue, such as glitter, obtained after drying has low adhesion to the surface of the cleaned material. Therefore, the dry residue left after the gel has dried can be easily removed by simple brushing and / or vacuuming. However, the dry residue can also be removed by a gas jet, for example, a jet of compressed air.

[0269] No rinsing is generally required and the process according to the invention does not generate any secondary effluent.

[0270] However, a light rinse, for example with water, of the treated surfaces, without mechanical action such as brushing, may exceptionally be necessary to remove any residual paint traces and slight gel residues.

[0271] According to the invention, this process first results in significant savings of chemical reagents compared to a decontamination process involving washing with a solution. Secondly, because the waste obtained is in the form of a dry residue that can be directly vacuumed, a rinsing operation with water or another liquid is generally avoided. This obviously leads to a reduction in the quantity of effluent produced, as well as a considerable simplification in terms of the treatment process and disposal. In particular, according to the invention, the waste obtained at the end of the treatment is not discharged into stormwater drainage systems in violation of regulations.

[0272] Due to the composition of the gel used according to the invention, the waste produced, once dry, represents only a small volume and is essentially mineral. It can therefore be stored or directed to a disposal channel without prior treatment.

[0273] As an 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 300 grams per m².

[0274] The invention will now be described with reference to the following examples, given by way of illustration and not limitation. Examples. Example 1.

[0275] This example describes the formulation of a gel according to the invention, called gel "Limo- 1”, used in examples 2 to 7.

[0276] The gel according to the invention, called "Limo-1" gel, is a gel whose composition is as follows: 10% by mass of fumed alumina, 90% by mass of an active agent which is d-limonene.

[0277] The alumina is Aeroxide ®< Alu C alumina marketed by EVONIK INDUSTRIES ®< which is a pyrogenated alumina with a specific surface area of ​​100 m 2< / g (BET), and the d-limonene is the d-limonene marketed by the company MERCK ®< .

[0278] This gel is prepared according to the following protocol: The d-limonene is first weighed in a suitable container.

[0279] d-Limonene is stirred using a mechanical stirrer, equipped with a three-bladed agitator, at a speed of 200 rotations / min., for 3 to 5 minutes.

[0280] Alumina, in a proportion of 10% by mass, is then gradually added to the d-limonene, which is stirred using a mechanical stirrer. As alumina is added, the viscosity of the stirred medium increases.

[0281] The rotation speed is therefore also gradually increased as the viscosity of the agitated medium increases, reaching approximately 400 to 600 revolutions per minute when all the alumina has been added, taking care to ensure that there are no projections.

[0282] The gel thus prepared is finally kept under agitation for 5 minutes, and left to rest for a period of at least one hour before use. Example 2.

[0283] In this example, the capacity of the gel according to the invention, called gel, is shown. “Limo-1”,Prepared in Example 1, this method is designed to remove bitumen stains from both dense, smooth surfaces and porous surfaces. The bitumen stains are created by depositing a small, slightly heated bead of bitumen onto the dense, smooth surface and the porous surface under a heavy load. The load is left for 24 hours to allow the bitumen to adhere properly to both the dense, smooth surface and the porous surface.

[0284] The gel according to the invention, called gel “Limo-1”, It is then applied, here with a spatula, in sufficient quantity to each of the bitumen stains and left to dry for 48 hours. Finally, the solid waste obtained after drying is collected by brushing.

[0285] There Figure 1 presents the results obtained on a dense, smooth epoxy resin surface.

[0286] We observe that, in one pass of the gel " Limo-1,The entire bitumen stain was successfully removed. One pass consists of applying the gel to the bitumen stain, allowing the applied gel to dry, and then brushing away the solid residue obtained after drying.

[0287] There Figure 2 presents the results obtained on a porous surface (concrete).

[0288] We observe that two successive passes of the frost "Limo-1 were necessary in order to remove the bitumen stain.

[0289] It is indeed necessary to optimize the ratio of quantity of gel to size of the bitumen stain in order to minimize the number of gel passes to be carried out.

[0290] These results thus demonstrate the ability of a gel according to the invention to completely or almost completely eliminate an organic matrix from a dense or porous surface. Example 3.

[0291] In this example, we describe the protocol for artificially contaminating bitumen with 137< Cs, which has been developed, and then we describe the preparation of a dense, smooth, epoxy resin support or surface contaminated by an adherent stain of this bitumen artificially contaminated with 137< Cs.

[0292] The contamination of the bitumen was set at 40,000 Bq / g in order to best simulate the bitumen stains present on the ground in nuclear facilities.

[0293] This protocol includes the following successive steps: 2 mL of an aqueous solution of 137< Cs at approximately 40,000 Bq / mL are deposited at the bottom of a dish (of the Petri dish type) with a fairly high rim.

[0294] This solution is then allowed to evaporate. The 137< Cs contamination is thus deposited labially at the bottom of the dish. Next, two grams of uncontaminated bitumen are placed in the small dish, which is then placed on a hot plate heated to 100°C for approximately one minute. The bitumen becomes much less viscous, almost liquid, and spreads to the bottom of the dish. The bitumen can then be slowly stirred in the dish with a spatula to evenly incorporate the ¹³⁷Cs contamination deposited at the bottom of the dish, as described above. The dish is held with insulated tongs to prevent any contact between the user and the hot plate and dish. Small beads of the contaminated bitumen, prepared in this way and still warm, are then placed on the surfaces to be contaminated. A sheet of parchment paper (which does not stick to the bitumen) is placed on top of the beads, and a light weight is applied to flatten them as much as possible.Finally, let it cool and rest for 24 hours.

[0295] Radiological activity measurements, namely a count, are carried out on each system consisting of a support, surface, and a contaminated bitumen stain, before carrying out the decontamination operation. Example 4.

[0296] In this example, the removal of a bitumen stain contaminated with 137Cs stuck to a dense surface is achieved, thus demonstrating the decontamination power of the gel according to the invention, called the " Limo-1, described in example 1, on a support, dense surface contaminated by an adherent stain of bitumen artificially contaminated by 137< Cs.

[0297] Bitumen artificially contaminated with 137< Cs is prepared according to the protocol described in Example 3, then a dense epoxy resin support or surface contaminated with an adherent stain of bitumen artificially contaminated with 137< Cs is prepared in accordance with Example 3 ( FIG. 3A After an initial measurement of the radiological activity, gel is applied with a spatula. "Limo-1" on the contaminated bitumen stain and then let it dry for 48 hours.

[0298] This produces glitter that can be easily brushed on ( FIG. 3B ).

[0299] A second count of radiological activity is then carried out and a first Decontamination Factor (DF) can be calculated.

[0300] We then obtain an FD of 23 for an initial contamination of 4600 Bq.

[0301] Applying a second layer of gel increases this FD to 156. Therefore, only very low contamination remains on the dense, smooth substrate ( FIG. 3C ).

[0302] The values ​​of radiological activities measured during the radiological decontamination operation carried out in example 4 are grouped in Table I below. Table I: Values ​​of radiological activities measured during the decontamination operation of a dense, smooth surface. Freeze Limo-1 Initial contamination (substrate + bitumen) (± 15%) 4600 Bq Contamination after 1 gel pass (± 5%) 199 Bq FD_1 23 Contamination after 2 gel passes (± 5%) 29 Bq FD_2 156

[0303] These results clearly demonstrate the effectiveness of the gel according to the invention, known as "gel". Limo-1 "for the decontamination of a substrate with a dense, smooth surface, such as an epoxy resin substrate contaminated by a contaminated bitumen stain. Example 5.

[0304] In this example, a bitumen stain contaminated with 137Cs and adhering to a porous surface is removed, thus demonstrating the decontamination power of the gel according to the invention, referred to as the gel. "Limo-1", described in example 1, on a support, a porous surface contaminated by an adherent bitumen stain artificially contaminated by 137Cs,

[0305] Bitumen artificially contaminated with 137< Cs is prepared according to the protocol described in example 3, then a support or porous concrete surface contaminated by an adherent stain of this bitumen artificially contaminated with 137< Cs is prepared in accordance with example 3.

[0306] After an initial count of the radiological activity, gel is applied with a spatula "Limo-1" on the contaminated bitumen stain and then let it dry for 48 hours.

[0307] This produces glitter that can be easily brushed off.

[0308] A second count of radiological activity is then carried out and a first Decontamination Factor (DF) can be calculated.

[0309] We then obtain an FD of 2 for an initial contamination of 5500 Bq.

[0310] Applying a second layer of gel allows an FD of 27 to be achieved.

[0311] Applying a third layer of gel allows an FD of 85 to be achieved.

[0312] Therefore, only very slight contamination remains on the porous surface.

[0313] The values ​​of radiological activities measured during the radiological decontamination operation carried out in Example 5 are grouped in Table II below. Table II: Values ​​of radiological activities measured during the decontamination operation of a porous surface. Freeze Limo-1 Initial contamination (frost + bitumen) (± 15%) 5500 Bq Contamination after 1 gel pass (± 15%) 2300 Bq FD_1 2 Contamination after 2 gel passes (± 5%) 205 Bq FD_2 27 Contamination after 3 gel passes (± 15%) 65 Bq FD_3 85

[0314] These results clearly demonstrate the effectiveness of the gel according to the invention, known as "gel". Limo-1 "for the decontamination of a support with a porous surface such as a concrete support contaminated by a contaminated bitumen stain. Example 6.

[0315] This example demonstrates the capacity of the gel according to the invention, called gel. "Limo-1 "to chemically attack an organic matrix such as an epoxy resin matrix."

[0316] For this, an optical profilometer is used which will allow the surface condition of an epoxy resin to be characterized before and after application of the gel.

[0317] There Figure 4A This presents a photograph of the surface of an epoxy resin before the application of a layer on the surface of the epoxy resin (left) and after the application of a layer of gel, the drying of this layer and the removal of the dried gel flakes (right).

[0318] There Figure 4B, shows the surface profiles corresponding to the surfaces photographed on the figure 4A , before the application of a layer on the surface of the epoxy resin (left) and after the application of a layer of gel, the drying of this layer and the removal of the dried gel flakes (right).

[0319] We observe that the epoxy resin is clearly degraded on the right side of the Figure 4A which shows the surface obtained after the deposition, drying and removal of the gel glitter "Limo-1".

[0320] This degradation occurs over a thickness of a few micrometers ( Figure 4B ).

[0321] These results thus demonstrate that the frost "Limo-1 "According to the invention, it attacks the epoxy resin to a thickness of a few microns.

[0322] This property will thus allow the gel according to the invention to release and then capture contaminants embedded under the surface (in subsurface) of this type of organic matrix. Example 7.

[0323] In this example, it is shown that the gel according to the invention, called gel "Limo-1 » prepared in example 1 can be implemented by spraying.

[0324] A rheological study of the gel « Limo-1» according to the invention, prepared in example 1 has been carried out and shows that this process is suitable for implementation by spraying.

[0325] For this type of gel to be applied by a spraying process, it must have the properties of a shear-thinning, thixotropic fluid, with a very short recovery time (less than one second), and it must have a yield stress (typically greater than 10-15 Pa).

[0326] Various rheological measurements were carried out using a TA Instruments ®< AR-IOOO rheometer in "Vane" geometry and are presented in this example.

[0327] Initially, the viscosity of the gel was measured as a function of the shear rate.

[0328] After a pre-shear of 5 minutes at a shear rate of 20 s -1<, then of 1 minute at 0.015 s -1<, several shear rate steps ranging from 0.015 s -1< to 100 s -1< are carried out with a viscosity measurement every 30 seconds.

[0329] There Figure 5 gives the evolution of the viscosity (Pa.s) of the gel « Limo-1» according to the invention as a function of the shear rate (s⁻¹) for shear rates between 0.015 and 100 s⁻¹. A linear (logarithmic) decrease in viscosity with the shear rate is observed, characteristic of the behavior of a shear-thinning fluid with yield stress.

[0330] There Figure 6 represents the shear stress value as a function of the deformation obtained at a given shear rate for the gel according to the invention, referred to as the "Limo-1" gel described in Example 1. A low shear rate (0.015 s⁻¹) is applied constantly to deform the gel from rest and thus determine the yield stress. A nearly steady flow is observed with shear stress values ​​exceeding 60 Pa. The yield stress of the material under very high deformation will therefore be well above 20 Pa, allowing the gel to adhere to a wall for thicknesses ranging from 0 to at least 2 mm.

[0331] In conclusion, this example shows that freezing « Limo-1 " according to the invention, it has the appropriate rheological properties allowing it to be very easily sprayed on horizontal or non-horizontal surfaces. Exemple 8.

[0332] In this example, it is shown that the gel according to the invention, called gel « Limo-1 » prepared in example 1 is aspirable after application and drying.

[0333] In other words, this example aims to show that the gel according to the invention, called gel « Limo-1 » prepared in example 1 fractures well, producing non-powdery flakes of millimeter size that can be easily aspirated.

[0334] To carry out this study, the Limo-1 gel is dried in a Binder® climate chamber where the temperature and relative humidity are set at 25°C and 50% respectively.

[0335] The gel is spread onto a machined stainless steel tray to achieve a controlled thickness of 2 mm of gel in the tray.

[0336] In the climate chamber, a Sartorius ®< precision balance is installed, as well as a Moticam ®< camera surrounded by a circular LED lamp (VWR) which is placed on top of the balance.

[0337] The balance and the Moticam ®< camera are connected to a computer located outside the climate chamber, thus enabling the simultaneous acquisition, during drying in a controlled atmosphere, of the mass and images of the gel-filled gondola.

[0338] It should be noted that the container holding the gel is placed inside the precision balance and that all the balance doors are closed, except for the door opposite the air supply fan for the climate chamber, which is opened by 3 cm to maintain the controlled atmosphere inside the balance chamber while limiting the airflow related to the operation of the climate chamber. Recording the mass during drying then allows for the plotting of a curve that shows the mass loss as a function of time and thus represents the drying kinetics.

[0339] The evolution of mass loss over time is presented on the Figure 7 , and a photograph showing the final size of the gel glitter is shown on the Figure 8 .

[0340] We thus observe a thickness of 2 mm of the gel « Limo-1 "It dries in a few hours, more precisely in about 1200 minutes, or 20 hours. It also appears that the number of flakes formed and especially their size is consistent with the fact that these flakes are millimeter-sized and not powdery. Exemple 9.

[0341] In this example, a bitumen stain is removed using a gel called « Limo-2 whose composition is as follows: 14% by mass of fumed alumina, 19% by mass of ethanol, 67% by mass of d-limonene

[0342] The alumina is Aeroxide®< Alu C, marketed by EVONIK INDUSTRIES®<, which is a fumed alumina with a specific surface area of ​​100 m² / g (BET), and the d-limonene is the d-limonene marketed by MERCK®<. The ethanol is marketed by MERCK®<.

[0343] This gel was prepared according to the protocol described in example 1.

[0344] A bitumen stain is created by depositing a small, slightly heated bead of bitumen onto a dense, smooth surface under a heavy load. The load is left on the stain for 24 hours to allow it to adhere properly to the surface.

[0345] The frost Limo-2 The product is then applied, here using a spatula, in sufficient quantity to the bitumen stain and left to dry for 48 hours. Finally, the solid waste obtained after drying is collected by brushing.

[0346] There Figure 9 presents the result obtained on a dense, smooth surface.

[0347] We observe that, in one pass of the gel " Limo-2», The entire bitumen stain was able to be removed.

[0348] One pass consists of applying the gel to the bitumen stain, allowing the applied gel to dry, and then brushing off the solid waste obtained after drying. REFERENCES

[0349] [1] FR-A1-2 827 530. [2] FR-A1-2 891470. [3] WO-A1-99 / 09134. [4] FR-A1-3 027 310. [5] FR-A1-2 957 929. [6] FR-A1-2962046 and WO-A1-2012 / 00104. [7] FR-A1-3003763 and WO-A1-2014 / 154818.

Claims

1. Suctionable gel for eliminating a contaminant species contained in a layer consisting of an organic material, on the surface of a solid substrate, consisting of a colloidal solution comprising, preferably consisting of: - 1% to 25% by weight, preferably 5% to 25% by weight, preferably 5% to 20% by weight, better yet 7% to 15% by weight, for example 10% to 14% by weight, based on the total weight of the gel, of at least one inorganic viscosifying agent consisting of one or more alumina(s) selected from among pyrogenic aluminas; - 13% to 99% by weight, preferably 80% to 95% by weight, for example 90% by weight, based on the total weight of the gel, of one or more organic solvent(s) selected from among the terpenes; - optionally from 1% to 40% by weight, preferably from 10% to 20% by weight, based on to the total weight of the gel, of ethanol; - optionally from 0.01% to 10% by weight, based on the total weight of the gel, of at least one dye and / or pigment; - optionally from 0.1% to 2% by weight, based on the total weight of the gel, of at least one surfactant; - optionally, from 0.1% to 10% by weight, preferably from 1% to 5% by weight, based on the total weight of the gel, of at least one agent extracting the contaminant species, for example of at least one agent extracting radionuclides, preferably selected from zeolites and clays.

2. Gel according to claim 1, wherein the terpenes are selected from among terpene hydrocarbons, oxygenated terpene compounds, and isomers, in particular optical isomers thereof; preferably the terpenes are selected from among ocimene, α-pinene, β-pinene, limonene, menthol, menthone, terpineol, isoborneol, camphor, nerol, citronellal, citronellol, myrcene, myrcenol, linalool, geraniol, and isomers in particular optical isomers thereof; preferably still, the gel comprises, as organic solvent selected from among terpenes, preferably as the only organic solvent selected from among terpenes, d-limonene.

3. Gel according to claim 2, comprising from 35% to 94% by weight, preferably from 65% to 83% by weight, preferably still from 70% to 80% by weight, for example 67% by weight, based on the total weight of the gel, of d-limonene, and from 1% to 40% by weight, preferably from 10% to 20% by weight, for example from 19% to 20% by weight, based on the total weight of the gel, of ethanol.

4. Gel according to any one of claims 1 to 3, wherein the alumina(s) represent(s) from 5% to 25% by weight, preferably from 7% to 15% by weight based on the total weight of the gel.

5. Gel according to any one of the preceding claims, wherein the surfactant is selected from among non-ionic surfactants such as block copolymers, like block copolymers of ethylene oxide and propylene oxide, and ethoxylated fatty acids; and the mixtures thereof.

6. Gel according to any one of the preceding claims, consisting of a colloidal solution comprising, preferably consisting of: - 1% to 25% by weight, preferably 5% to 25% by weight, preferably still 5% to 20% by weight, better yet 7% to 15% by weight, for example 10% to 14% by weight, based on the total weight of the gel, of at least one pyrogenic alumina; - 35% to 94% by weight, preferably 65% to 83% by weight, more preferably 70% to 80% by weight, for example 67% by weight, based on the total weight of the gel, of d-limonene ; - from 1% to 40% by weight, preferably from 10 to 20% by weight, for example 19% to 20% by weight, based on the total weight of the gel, of ethanol.

7. Method for eliminating a contaminant species contained in a layer consisting of an organic material on the surface of a solid substrate, wherein at least one cycle is carried out comprising the following successive steps: a) applying the suctionable gel according to any one of claims 1 to 6, onto said layer consisting of an organic material; preferably, the gel is applied by means of spraying, with a brush or with a trowel; b) maintaining the gel on the layer consisting of an organic material at least for a period of time that is sufficient in order for the gel to dissolve partly or totally, the organic material of the layer consisting of an organic material; to absorb the contaminant species (in order for the contaminant species to migrate into the gel); and in order for the gel to dry and form a dry, solid, and non-pulverulent residue containing the organic material of the layer consisting of an organic material that has been dissolved, and the contaminant species; c) eliminating the dry and solid residue containing the organic material of the organic layer that has been dissolved, and the contaminant species; preferably the dry and solid residue is eliminated from the surface of the solid substrate by means of brushing and / or suctioning.

8. Method according to claim 7, wherein the contaminant species is a contaminant species that is radioactive, and / or chemically toxic, and / or toxic on account of its shape and / or of its size; preferably, the contaminant species which is toxic on account of its shape and / or of its size is a contaminant species that is in the form of solid particles such as microparticles, or nanoparticles, for example in the form of fibres such as microfibres or nanofibres, in the form of nanotubes, or in the form of crystals such as nanocrystals.

9. Method according to according to any one of claims 7 to 8, wherein the contaminant species is selected from among metals and metalloids in the form of a metal, a metalloid, or in ionic form, preferably from among metals referred to as "heavy metals", and toxic metals and metalloids in the form of a metal, a metalloid, or in ionic form; the compounds of these metals and metalloids such as organometallic compounds, metal salts, metal oxides, metal carbides, etc; ceramics; and glasses for example in the form of glass wool; preferably the metals referred to as "heavy metals", and the toxic metals and metalloids are antimony, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tellurium, thallium, and tin.

10. Method according to claim 9, wherein the contaminant species is asbestos.

11. Method according to any one of claims 7 to 10, wherein the layer constituted of an organic material containing a contaminant species is a surface layer of a solid substrate consisting of the said (the same) organic material, preferably this organic material is selected from among paints, lacquers, organic polymers, and organic resins such as epoxy resins; preferably the solid substrate consisting of an organic material is a bulk solid substrate or a layer, such as a layer of paint or of epoxy resin, for example a layer of paint or of epoxy resin forming a coating on a surface of a substrate.

12. Method according to any one of claims 7 to 11, wherein the layer consisting of an organic material containing a contaminant species, is a layer that is found on a surface of a solid substrate, this layer being present in the form of a continuous layer, or in the form of a spot, or discrete spots of the organic material containing a contaminant species; preferably, the organic material is selected from sticky organic materials.

13. Method according to claim 12, wherein the organic material is selected from oils, such as hydrocarbon oils, bitumens, tars and greases.

14. Method according to any one of claims 7 to 13, wherein the gel is applied on to the surface layer in a proportion of 100 g to 10000 g, preferably from 500 g to 5000 g of gel per m2 of surface area, more preferably from 500 to 1500 g of gel per m2 of surface area, better still from 600 to 1000 g of gel per m2 of surface area, which generally corresponds to a thickness of gel deposited on the surface from 0.1 mm to 1 cm, preferably from 0.5 mm to 5 mm.

15. Method according to any one of claims 7 to 14, wherein the gel is maintained on the surface for a period of 2 hours to 72 hours, preferably from 4 to 48 hours, more preferably from 6 to 24 hours.

16. Method according to any one of claims 7 to 15, wherein the dry and solid residue is in the form of particles, for example flakes, of a size of 1 to 10 mm, preferably from 2 to 5 mm.

17. Method according to any one of claims 7 to 16, wherein the cycle is repeated from 1 to 10 times by using the same gel during all the cycles or by using different gels during one or more cycle(s).

18. Method according to any one of claims 7 to 17, wherein during step b), the gel, before total drying, is rewetted with a solvent, preferably with the solvent of the gel applied during step a).