Iron oxide filter material for eliminating heavy metals in wastewater

Abstract

The present invention relates to a filter material for eliminating heavy metals in water, said material comprising an iron material made up of at least 50% of a mixture of iron oxides, said iron material having a particle size distribution of less than 300 μm. The invention further relates to a filter material comprising the previous filter material microencapsulated in one or more biodegradable polymers, wherein the one or more biodegradable polymers are selected from the group consisting of alginate, polyvinyl alcohol, carboxymethyl cellulose and chitosan.

Description

[0001] IRON OXIDE FILTER MATERIAL FOR THE REMOVAL OF HEAVY METALS IN WASTEWATER

[0002] TECHNICAL FIELD

[0003] The present invention relates to the field of environmental and chemical engineering, specifically to the use of iron materials and microencapsulation techniques for the filtration and removal of heavy metals in wastewater generated by industries such as mining, the removal of metalloids such as arsenic in natural waters containing high concentrations of this element, and the non-ferrous metal industry, among others. The invention addresses the problem of fluid contamination through the use of iron oxides and microencapsulated iron oxides in a biopolymeric matrix, and the microencapsulation method for obtaining them.

[0004] BACKGROUND OF THE INVENTION

[0005] The generation of wastewater with high heavy metal content in various industries, such as mining and the non-ferrous metal industry, represents a significant environmental problem. The presence of heavy metals in these wastewaters can have harmful effects on both aquatic ecosystems and human health. The physicochemical properties of iron compounds, such as the ability to form coordination complexes, high adsorption capacity, the ability to reduce metal ions by decreasing their solubility, or the formation of insoluble compounds with other metals, can cause the agglomeration of these substances, allowing their elimination. However, other characteristics of iron compounds, such as the formation of hydrogen bonds or magnetic attraction, hinder their application in filtration systems for the removal of heavy metals from contaminated water.Therefore, there is a need to develop technologies that improve the usefulness of iron materials in water filtration systems. Currently, various techniques are applied to treat water contaminated with heavy metals, such as the use of ion exchange resins, precipitation, reverse osmosis, and adsorption with various adsorbents. However, the costs and toxicity associated with the technologies and materials used in these processes, particularly the adsorbents, have generated the need to find new, low-cost, and less toxic materials that can be used as adsorbents.

[0006] Patent application CN107376829 provides a method for preparing an adsorbent from iron-containing fly ash for arsenic removal. The method involves sieving, chemically treating, and grinding fly ash to a level of iron oxides, which are then used to treat water streams and remove arsenic. This method uses iron as part of a non-encapsulated filter material for arsenic removal, which must be obtained through an energy-intensive chemical process that also uses expensive reagents. Consequently, this technology does not address the disadvantages associated with iron oxides in heavy metal filtration.

[0007] Currently, there are no iron-based filter materials that are easily obtained, low in value, low in toxicity, and highly effective in removing heavy metals.

[0008] The present invention is based on the use of a steelmaking residue, known as flake, derived from the hot-rolling process, in encapsulated or non-encapsulated form, for the removal of heavy metals from contaminated water bodies. This innovative solution takes advantage of the adsorption properties of iron oxides present in the flake, being economical and easy to obtain, and at the same time, its encapsulation in polymer matrices prevents its agglomeration.

[0009] SUMMARY OF THE INVENTION

[0010] The present invention relates to a filter material for removing heavy metals from water, comprising an iron material composed of at least 50% of a mixture of iron oxides. In a preferred embodiment, the iron material has a particle size of less than 500 µm, preferably less than 400 µm, more preferably less than 300 µm, more preferably less than 200 µm, more preferably less than 100 µm, and even more preferably less than 70 µm.

[0011] In another preferred embodiment, the iron material is microencapsulated in one or more biodegradable polymers, where the one or more biodegradable polymers are selected from the group consisting of alginate, polyvinyl alcohol, carboxymethyl cellulose and chitosan;

[0012] In another preferred embodiment of the invention, the iron material has a mass of 1 to 50% of the total biodegradable polymer mass.

[0013] In another preferred embodiment, the iron oxides are selected from the group consisting of: a-Fe2O3, [3-Fe2O3, FesC, ZnFe2O4 and FeMnOs.

[0014] With a view to meeting the needs of the state of the art, the present invention provides a method for obtaining a filter material for removing heavy metals from water, comprising an iron material microencapsulated in one or more biodegradable polymers, comprising the steps of: a) mixing a solution comprising one or more biodegradable polymers selected from the group consisting of alginate, polyvinyl alcohol, carboxymethyl cellulose and chitosan; with an iron material with a particle size of less than 100 pm and composed of at least 50% of a mixture of iron oxides; b) subjecting the biodegradable polymer solution and the iron material to sonication; c) adding dropwise the solution comprising one or more biodegradable polymers and the iron material to a precipitation solution to obtain microcapsules (or microcapsules, to standardize terminology) in the precipitation solution;d) shaking the precipitation solution with the microcapsules for more than 3 hours to allow polymer crosslinking; and e) washing the microcapsules with water.

[0015] In a preferred embodiment, the total amount of the one or more biodegradable polymers is between 1 and 8% w / v.

[0016] In another preferred embodiment, the one or more biodegradable polymers are 5% w / v polyvinyl alcohol and 1.5% w / v sodium alginate.

[0017] In another preferred embodiment, the one or more biodegradable polymers are 2% w / v carboxymethyl cellulose and 2% w / v sodium alginate.

[0018] In another preferred embodiment, the one or more biodegradable polymers are 1% w / v chitosan and 2.5% w / v sodium alginate.

[0019] In another preferred embodiment, the iron material is added in an amount between 1 and 50% of the biodegradable polymer mass.

[0020] In an alternative embodiment, one or more of the one or more biodegradable polymers form part of the precipitation solution.

[0021] In another preferred embodiment, the precipitation solution comprises CaCh and an acid selected from the group consisting of HBO3 and acetic acid.

[0022] In another preferred embodiment, the CaCh is at a concentration between 2 and 4% w / v.

[0023] In another preferred embodiment, HBO3 is at a concentration between 1 and 3% w / v.

[0024] In another preferred embodiment, the acetic acid is at a concentration between 1 and 5% v / v.

[0025] In order to meet the needs of the prior art, the present invention also provides a method for removing heavy metals from water using the filter material described above, comprising the steps of: a) passing water contaminated with heavy metals through the filter material, allowing the heavy metals to be retained; b) recovering the water with a reduced concentration of heavy metals. In a preferred embodiment, the filter material is provided within a filter device.

[0026] BRIEF DESCRIPTION OF THE FIGURES

[0027] FIG. 1 shows the arsenic sorption kinetics of the different materials conditioned according to their particle size; (FIG. 1 A) samples conditioned with HCl and (FIG. 1 B) samples conditioned with NaOH.

[0028] FIG. 2 shows the percentage of copper removal over time at different flake concentrations.

[0029] FIG. 3 shows the percentage of cadmium removal over time at different flake concentrations.

[0030] FIG. 4 shows the percentage of zinc removal over time at different flake concentrations.

[0031] FIG. 5 shows the percentage of lead removal over time at different flake concentrations.

[0032] FIG. 6 shows the growth percentage of HepG2 (human hepatocytes) and Vero (kidney cells) cell lines exposed to different particle sizes of the film, with and without arsenic.

[0033] DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention is directed to a filter material, in particular to a microencapsulated iron material in one or more biodegradable polymers, the use of which makes it possible to remove heavy metals from water streams, ultimately avoiding environmental and human problems caused by this type of pollutants.

[0035] All technical and scientific terms used to describe this invention have the same meaning as understood by a person with basic knowledge in the technical field concerned. However, to more clearly define the scope of the invention, a list of the terminology used in this description is included below.

[0036] The term "flake" refers to the waste generated during the hot-rolling process of steel. More specifically, flake is the thin, flaky material that is removed from the surface of the steel during the hot-rolling process. This process involves heating the steel to a very high temperature, followed by deformation under pressure to form sheets of steel of varying thicknesses. During this process, the steel surface can oxidize due to exposure to air and extreme heat. This rust is removed in the form of thin flakes or "flakes" when the steel is subjected to pressure on the rolling rolls. Although flake is a waste product of the rolling process, it can be recycled and used in other industrial processes, such as cement manufacturing or other applications.

[0037] The term "heavy metals" refers to a category of metals and metalloids that are physically and chemically dense or have the potential for toxicity, even at low exposure levels. Although there is no accepted standard definition for the term "heavy metals," it generally refers to those elements with an atomic number greater than 20 and a density greater than 5 g / cm 3 Common examples of heavy metals include, but are not limited to: Lead (Pb), Mercury (Hg), Cadmium (Cd), Arsenic (As), Chromium (Cr), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Tin (Sn), Molybdenum (Mo), Vanadium (V), Barium (Ba), Manganese (Mn), among others.

[0038] The term "filter media" refers to any type of material, substance, or compound used in a filtration process to separate solid particles from a fluid, such as a gas or liquid. This material can be physical, chemical, or biological in nature, and its choice depends on the type of particles to be filtered, the particle size, the properties of the fluid, and the specific requirements of the filtration process. Filter media can be porous or nonporous and vary in size, shape, density, and material. Some common examples of filter media include filter paper, polymer membranes, activated carbon, sand, synthetic glass, ceramics, fabrics and fibers of various materials, microcapsules, among others.In use, the fluid is passed through the filter material, and solid particles are captured and retained in the material due to mechanisms such as physical interception, chemical adsorption or biological action, while the filtered fluid passes through said material.

[0039] The term "filter device" refers to a device or apparatus used to separate and remove particles, contaminants, or certain undesirable chemical components from a solution or mixture through a process known as filtration. Filtration is a physical or chemical process by which solids, liquids, or gases are separated by a filter material. This allows some elements or compounds to pass through while retaining others, depending on the physical and chemical properties and the structure of the filter material. In the case of water filtration, filter devices can range from devices such as ceramic or activated carbon filters to more advanced technologies such as membrane filtration, adsorption filtration, ion-exchange filtration, and reverse osmosis filtration.In particular, the removal of heavy metals from water, such as lead, mercury, cadmium, and arsenic, is of utmost importance due to their detrimental effects on human health.

[0040] The term "crosslinking" or "reticulation" refers to the formation of covalent bonds between the polymer molecules that make up the microcapsule wall. This process increases the microcapsule's strength and stability, allowing for controlled and targeted release of the encapsulated contents. Crosslinking is generally carried out using specific crosslinking agents that can react with the functional groups present in the polymer molecules. Examples of these crosslinking agents include, but are not limited to: Glutaraldehyde: This is one of the most common crosslinking agents. It is used in the crosslinking of proteins and polymers containing amino groups. Formaldehyde: It is used to crosslink polymers containing amino groups, such as proteins and certain polysaccharides.Ethylene glycol dimethasone (EGDMA) and Tetraethylene glycol dimethasone (TEGDMA): These are used to crosslink polymers containing vinyl groups such as polystyrene. Genipin: A natural crosslinking agent used to crosslink polymers containing amino groups such as chitosan and gelatin. 1- Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDO): Used in combination with N- Hydroxysuccinimide (NHS) to crosslink polymers containing carboxyl and amino groups. Divinyl sulfone (DVS): Used to crosslink polymers containing hydroxyl groups such as dextran and hydroxyethylcellulose. The degree of crosslinking can be adjusted to control the properties of the microcapsule, including its permeability and resistance to degradation.Furthermore, cross-linking can be used to modify the microcapsule's response to specific stimuli, such as changes in pH, temperature, or the presence of certain molecules, allowing for the controlled release of the encapsulated contents in response to these conditions. In a less strict sense, and for the purposes of the present invention, the term "cross-linking" should also be understood as the ionic interaction between certain compounds and polymers that allows the formation of gels or solid matrices. For example, calcium chloride is commonly used in the encapsulation technique known as ionic gelation. In this process, a negatively charged polymer, such as alginate, is mixed with a calcium chloride solution. The calcium ions interact with the charged groups of the polymer, forming a gel or solid matrix that encapsulates the material of interest.In this application, this process will be considered and referred to as a cross-linking process.

[0041] The present invention relates to a filter material for the removal of heavy metals from water, comprising an iron material composed of at least 30%, preferably 40%, and more preferably 50%, of a mixture of iron oxides.

[0042] In a preferred embodiment, the iron material has a granulometry of less than 500 pm, preferably less than 400 pm, more preferably less than 300 pm, more preferably less than 200 pm, more preferably less than 100 pm, and even more preferably less than 70 pm.

[0043] The iron material used in the present invention comes from the metallurgical residue known as flake. In a preferred embodiment, the flake is treated with one or more compounds selected from the group consisting of sodium hydroxide (NaOH), hydrogen chloride (HCl), sodium borohydride (NaBH), and hydrogen peroxide (H2O2).

[0044] In another preferred embodiment, the treatment of the slide comprises introducing the slide into a 2M hydrochloric acid solution; incubating for 30 minutes with shaking; orbitally shaking for 24 hours at 100 RPM; separating the slides from the solution by filtration, washing with distilled water, drying at 60°C for 6 hours, adding 30% v / v H2O2 and incubating for 4 hours.

[0045] In another preferred embodiment, the iron material is microencapsulated in one or more biodegradable polymers, where the one or more biodegradable polymers are selected from the group consisting of alginate, polyvinyl alcohol, carboxymethyl cellulose and chitosan;

[0046] Regarding the one or more biodegradable polymers, alginate is a linear polysaccharide extracted primarily from brown seaweed. It consists of 3-D-mannuronic acid (M) and α-L-guluronic acid (G) monomers, linked by glycosidic bonds. The sequence and length of the M and G blocks can vary, giving rise to a variety of physical and chemical properties. Alginate has the ability to form gels in the presence of divalent cations, such as calcium. This property makes it an excellent material for microencapsulation due to its ability to form a gel matrix that can protect the encapsulated cells or compounds.

[0047] Polyvinyl alcohol, or polyvinyl alcohol, is a polymer derived from the polymerization of vinyl monomers. Polyvinyl alcohol is useful in microencapsulation due to its chemical resistance and stability. Furthermore, it can be easily modified to improve specific properties.

[0048] Carboxymethylcellulose (CMC) is a modified polysaccharide derived from cellulose, an abundant natural polysaccharide. Cellulose consists of glucose units linked by (3-1,4-O-glucosidic bonds. In CMC, some of the hydroxyl (OH) groups of glucose have been replaced by carboxymethyl (-CH2-COOH) groups, giving CMC water-retaining and swelling properties. Chitosan is a linear polysaccharide composed of repeating units of D-glucosamine and N-acetyl-D-glucosamine, linked by (3-1,4-glucosidic bonds. The chemical structure of chitosan gives it unique properties such as the ability to form films and gels, making it an excellent material for microencapsulation.

[0049] The polymers described above allow the iron material to be microencapsulated to prevent agglomeration, thus improving its usefulness in water filtration systems.

[0050] On the other hand, the fact that the iron material is composed of a mixture of iron oxides allows the capture of heavy metal particles due to the physicochemical properties of these iron oxides.

[0051] The particle size of the iron material allows for the generation of an ideal area of ​​action for the retention of heavy metal particles, thus efficiently removing these contaminants by passing water masses through the filter material previously described.

[0052] In a preferred embodiment of the invention, the iron material has a mass of 1 to 50% of the total biodegradable polymer mass. This allows for a sufficient proportion of biodegradable polymer to iron material, such that the filter material microcapsules are stable and functional over time.

[0053] In another preferred embodiment, the iron oxides are selected from the group consisting of: a-Fe2C>3, [3-Fe2O3, FesCM, ZnFe2C>4 and FeMnOs. These iron oxides are easily obtained since they are part of the waste from the steel industry (flake), and they have the previously described physicochemical properties that allow the retention of heavy metals present in the water.

[0054] In order to meet the needs of the state of the art, the present invention provides a method for obtaining a filter material for removing heavy metals from water, comprising an iron material microencapsulated in one or more biodegradable polymers, comprising the steps of: a) mixing a solution comprising one or more biodegradable polymers selected from the group consisting of alginate, polyvinyl alcohol, carboxymethyl cellulose and chitosan; with an iron material as described above; b) subjecting the solution of biodegradable polymer and iron material to sonication; c) adding dropwise the solution comprising one or more biodegradable polymers and iron material to a precipitation solution to obtain microcapsules in the precipitation solution; d) stirring the precipitation solution with the microcapsules for a time greater than 3 hours so that polymer crosslinking occurs;and e) wash the microcapsules with water.;

[0055] These steps produce microcapsules of microencapsulated iron filter material that are effective and environmentally friendly for removing heavy metals from water, which is of vital importance for environmental protection and public health.

[0056] Specifically, sonication involves using sound waves to agitate the mixture, ensuring uniform dispersion of the iron material within the polymers. Cross-linking strengthens the structure of the filter material and improves its stability.

[0057] In a preferred embodiment, the total amount of the one or more biodegradable polymers is between 1 and 8% w / v;

[0058] In another preferred embodiment, the one or more biodegradable polymers are polyvinyl alcohol at 2% to 8% w / v and sodium alginate at 1% to 2% w / v. In another more preferred embodiment, the one or more biodegradable polymers are polyvinyl alcohol at 5% w / v and sodium alginate at 1.5% w / v.

[0059] In another preferred embodiment, the one or more biodegradable polymers are carboxymethyl cellulose between 1% and 3% w / v and sodium alginate between 1% and 3% w / v. In another more preferred embodiment, the one or more biodegradable polymers are carboxymethyl cellulose at 2% w / v and sodium alginate at 2% w / v. In another preferred embodiment, the one or more biodegradable polymers are chitosan between 0.5% and 1.5% w / v and sodium alginate between 1% and 4% w / v. In another more preferred embodiment, the one or more biodegradable polymers are chitosan at 1% w / v and sodium alginate at 2.5% w / v.

[0060] In another preferred embodiment, the iron material is added in an amount between 1 and 50% of the biodegradable polymer mass.

[0061] In an alternative embodiment, one or more of the biodegradable polymers are part of the precipitation solution. In this embodiment, the biodegradable polymer(s) that are part of the precipitation solution become part of the microcapsules when the solution comprising the iron material is added to the precipitation solution.

[0062] In another preferred embodiment, the precipitation solution comprises CaCl and an acid selected from the group consisting of HCl and acetic acid. In this case, CaCl acts as a cross-linking agent, while boric acid can form stable bonds with hydroxyl groups in certain polymers, such as polysaccharides, forming a three-dimensional structure. This is used to stabilize polysaccharide gels and films. Both acetic acid and boric acid then modify the solubility conditions of the different polymers, optimizing the encapsulation conditions.

[0063] In another preferred embodiment, the CaCh is at a concentration between 1 and 5% w / v, more preferably between 2 and 4% w / v.

[0064] In another preferred embodiment, HBO3 is at a concentration between 0.1 and 4% w / v, more preferably between 1 and 3% w / v.

[0065] In another preferred embodiment, the acetic acid is at a concentration between 0.1 and 6% v / v, more preferably between 1 and 5% v / v.

[0066] Another object of the invention relates to a filter material for removing heavy metals from water, comprising an iron material composed of at least 30%, preferably 40%, and more preferably 50%, of a mixture of iron oxides; and the iron material has a particle size of less than 500 pm, preferably less than 400 pm, more preferably less than 300 pm, more preferably less than 200 pm, more preferably less than 100 pm, and even more preferably less than 70 pm.

[0067] The iron material used comes from the metallurgical residue known as flake. In a preferred embodiment, the flake is treated with one or more compounds selected from the group consisting of sodium hydroxide (NaOH), hydrogen chloride (HCl), sodium borohydride (NaBH), and hydrogen peroxide (H2O2).

[0068] In a preferred embodiment, the treatment of the slide comprises introducing the slide into a 2M hydrochloric acid solution; incubating for 30 minutes with shaking; orbitally shaking for 24 hours at 100 RPM; separating the slides from the solution by filtration, washing with distilled water, drying at 60°C for 6 hours, adding 30% v / v H2O2 and incubating for 4 hours.

[0069] In a preferred embodiment, the iron oxides are selected from the group consisting of: a-Fe2C>3, [3-Fe2O3, FesCM, ZnFe2C>4 and FeMnOs. These iron oxides are easily obtained since they are part of the waste from the steel industry (flake), and they have the previously described physicochemical properties that allow the retention of heavy metals present in the water.

[0070] In order to meet the needs of the state of the art, the present invention provides a method for removing heavy metals from water using the filter material previously described, comprising the steps of: a) passing the water contaminated with heavy metals through the filter material, allowing the heavy metals to be retained; b) recovering the water with a reduced concentration of heavy metals.

[0071] In a preferred embodiment, the filter material is provided within a filter device. Preferably, the filter device is selected from the group consisting of: sand filter, cartridge filter, deep bed filter, mesh filter, ceramic filter, among others. EXAMPLES OF EMBODIMENT

[0072] The following examples are intended to illustrate the invention and its preferred embodiments, but under no circumstances should they be considered to restrict the scope of the invention, which will be defined by the tenor of the claims appended hereto.

[0073] Example 1. Sorption tests

[0074] Arsenate removal studies were conducted in batch systems, evaluating kinetic and thermodynamic parameters of the lamellae in different sizes. These sorption tests determined the removal capacities of the different materials as a function of pH, time, and arsenate concentration. A total of 1,260 samples were evaluated, divided into 210 for the sorption-pH axis, 720 for kinetics, and 330 for isotherms.

[0075] In this context, the effect of pH on arsenate removal was evaluated for different material sizes, compared to the two strongest market competitors, commercially known as Ferrolox and Bayoxide. The study was carried out over a pH range of 3 to 9, considering an arsenate concentration of 200 ppm. An important parameter in removal studies is the equilibrium time, which was obtained through sorption kinetic studies. 20 mL of a solution of 10 and 50 mg L-1 of As(V) with 0.01 M NaCl, adjusted to the optimal pH for As removal, determined by the previous test, were considered. The times considered were from 5 to 1440 minutes, and the quantification of total As was determined by means of flame atomizing atomic absorption spectroscopy.

[0076] The results obtained for As(V) removal as a function of pH showed that the samples were favored within a pH range between 5.5 and 7.5, achieving a 30% removal for the largest granulometry materials (200-315 pm), offering an As(V) concentration of 50 ppm. This value is above the standard established for domestic water. Once the pH for highest removal was established, tests were performed to evaluate the effect of contact time. Equilibrium time was reached at approximately 200 minutes for most materials. Differentiated kinetic behavior was observed in the samples when different concentrations of As(V) were applied. When the concentration of this analyte offered was 10 ppm, the highest removal capacity was obtained for samples with a size between 150-63 pm and > 3.15 mm, while the samples treated with 50 ppm the maximum sorption capacity was for the Lamella <63 pm.

[0077] The above results can be seen in FIG. 1 . The differences can be attributed to the high heterogeneity of the samples and the fact that they offer high concentrations of As(V), would favor the formation of multilayers, in addition to possible transformations on the surface of these substrates. The data obtained from the sorption kinetics were interpreted by applying two kinetic models (pseudo-first and second order). The pseudo-first order model showed the best fit, however, given the working pH conditions (pH=6.5) the As(V) is dissociated.

[0078] Sorption experiments were also performed at different flake concentrations to remove copper, cadmium, zinc, and lead. High removal rates were observed for all of these, as can be seen in FIGS. 2, 3, 4, and 5.

[0079] Example 2. Toxicity tests

[0080] Cytotoxicity assays were performed on the original material in its various sizes. The objective was to determine the effect on hepatocyte and kidney cell lines over periods of 24, 48, and 72 hours. The tests were performed on the HepG2 (human hepatocytes) and Vero (kidney) cell lines. Each assay was performed in triplicate, with three sub-replicates for each sample. Each of these assays was repeated three times for each cell line, resulting in a total of 1,350 samples analyzed.

[0081] The results obtained showed that the materials under study did not affect the growth of cell lines in all the size ranges analyzed. Therefore, it was concluded that they did not exhibit any degree of cytotoxicity. These results can be seen in FIG. 6.

[0082] Example 3. Preparation of microcapsules with 2.5% w / v sodium alginate

[0083] A 100 mL solution of 2.5% w / v sodium alginate (AlgNa) was prepared. To do this, 100 mL of milliQ water was measured using a volumetric flask and transferred to a 250 mL Schott flask. A 2.5 g mass of AlgNa was then slowly added until completely dissolved. The solution was heated on a hot plate at 60°C with constant stirring, generating a viscous solution that was left to cool for 24 hours. For capsule precipitation, the AlgNa solution was sonicated for 2 hours to eliminate bubbles. Equipment was assembled with a medium-sized outlet stopcock and medium-sized hose. 50 mL of milliQ water was passed through at 10 rpm, the hose was priming with the AlgNa solution at the same speed, and then the pump speed was reduced to 4 rpm. The AlgNa capsules were received on 300 mL of calcium chloride (CaCI2) at 3% W / V, with plate shaking.This mixture was transferred to a 500 mL Schott flask and allowed to crosslink overnight under constant refrigeration. The capsules were washed with abundant milli-Q water, approximately 600 mL, in a one-liter beaker. They were separated from the liquid using a strainer, and this procedure was continued until translucent capsules were obtained. Finally, the capsules were stored in 500 mL Schott flasks and refrigerated for 24 hours. Additionally, 1 liter of 3% w / v (0.05 M) CaCl2 was prepared. 30 g of calcium chloride were weighed, dissolved in a volume of less than 1 liter (approximately 400 mL) of milli-Q water, and transferred to a 1-liter volumetric flask. The prepared solution was shaken and calibrated.

[0084] Example 4. Preparation of microcapsules with 5% w / v polyvinyl alcohol and 1.5% w / v sodium alginate

[0085] A solution of 5% w / v polyvinyl alcohol (PVA) and 1.5% w / v sodium alginate (AlgNa) was prepared. Initially, 50 mL of milliQ water was measured using a volumetric flask and transferred to a 250 mL Schott flask. This was heated on a hot plate to 100°C with stirring. A mass of 5 g of PVA was slowly added until completely dissolved. Subsequently, the temperature was reduced to 60°C, and an additional 50 mL of milliQ water was added, measured using a volumetric flask. A mass of 1.5 g of AlgNa was then gradually incorporated until completely dissolved. The resulting viscous solution was refrigerated. For capsule precipitation, the AlgNa solution was sonicated for 2 hours to remove bubbles. Then, a device was assembled with a medium outlet valve and a medium hose, and the hose was primed with the 5% W / V AlgNa 1.5% W / V PVA solution at 10 rpm.The resulting capsules of 5% PV AlgNa, 1.5% W / V were collected on 300 mL of 2% W / V HBO3 / 3% W / V CaCh3 with a stirring plate. The height of the stopcock was reduced to half the universal support to prevent bubble formation. The capsules were transferred to a 500 mL Schott flask with the solution and refrigerated. The capsules were left to crosslink overnight in the precipitating solution and refrigerated. To wash the capsules, they were rinsed with abundant milliQ water, approximately 600 mL, in a one-liter beaker. They were then separated from the liquid using a strainer and this procedure was continued as many times as necessary until translucent capsules were obtained. The capsules were stored in 500 mL Schott flasks, labeled, and refrigerated for 24 hours. In addition, one liter of 2% W / V HBO3 / 3% W / V CaCh was prepared. 30.0048 g of CaCh were weighed and dissolved in 500 mL of milli Q water in a one-liter beaker.The solution was placed on a hot plate with constant stirring and the temperature raised to approximately 30°C. 20.0095 g of HBO3 were added until completely dissolved, with additional milliQ water added if necessary. The solution was allowed to cool to room temperature, transferred to a one-liter volumetric flask, stirred, and topped up to the mark.

[0086] Example 5. Preparation of microcapsules with 5% w / v polyvinyl alcohol, 1.5% w / v sodium alginate, and 5% w / v lamella (relative to the polymer mass)

[0087] A solution of 100 mL of 5% W / V PVA, 1.5% W / V AlgNa, and 5% W / V flake (based on the polymer mass) was prepared. To prepare the solutions, 75 mL of milliQ water was measured using a 50 and 25 mL flask and transferred to a 250 mL Schott flask. This solution was heated on a hot plate to 100°C with constant stirring. A mass of 5.0014 g of PVA was then slowly added until completely dissolved. The temperature was gradually lowered to 60°C, then a mass of 1.5010 g of AlgNa was added little by little to the hot solution. The mixture was stirred until completely dissolved. A 0.3254 g quantity of flake, corresponding to 5% W / V of the total polymer mass, was then weighed into a small 50 mL beaker. These were then added to the previous polymer mixture with the help of the remaining 25 mL of milli-Q water.

[0088] For capsule precipitation, the AlgNa solution was sonicated for two hours to eliminate bubbles. Equipment was set up with a medium-sized outlet stopcock and a medium-sized hose, allowing 50 mL of milli-Q water to pass through at 10 rpm. The hose was priming with the 5% w / v PVA / 1.5% w / v AlgNa solution at 10 rpm. The 5% w / v PVA and 1.5% w / v AlgNa capsules were placed on 300 mL of 2% w / v HBO3 / 3% w / v CaCh3 with a stirring plate. The height of the stopcock was lowered to half the universal support to prevent bubble formation. The solution was transferred to a 500 mL Schott flask and refrigerated. The capsules were allowed to crosslink overnight in the precipitating solution and refrigerated. The capsules were washed with plenty of milli-Q water, approximately 600 mL in a one-liter beaker. They were then separated from the liquid using a strainer.This procedure was repeated as many times as necessary until translucent capsules were obtained. Finally, the capsules were stored in 500 mL Schott flasks and refrigerated.

[0089] Example 6. Preparation of microcapsules with 2% w / v carboxymethylcellulose and 2% w / v sodium alginate

[0090] A solution of 100 mL of 2% W / V CMC (carboxymethylcellulose) and 2% W / V AlgNa (sodium alginate) was prepared. To do this, 50 mL of milliQ water was initially measured using a volumetric flask and transferred to a 50 mL Schott flask. The water was heated to 100°C on a hotplate with stirring. A 2.0 g mass of CMC was then slowly added until it was completely dissolved. The temperature was then reduced to 60°C and an additional 50 mL of milliQ water was added, measured using a volumetric flask. While maintaining the temperature of the hotplate at 60°C, a 2.0 g mass of AlgNa was added little by little until it was completely dissolved. The resulting viscous solution was cooled.

[0091] Capsule precipitation was achieved by sonicating the AlgNa solution for 2 hours to eliminate bubbles. Equipment was assembled with an outlet stopcock and a medium-sized hose. Fifty mL of milli-Q water was allowed to pass through at 10 rpm, and the hose was saturated with the 2% CMC and 2% AlgNa solution at the same speed of 10 rpm. The 2% w / v CMC and 2% w / v AlgNa capsules were collected over 300 mL of 3% w / v CaCl2 with a stirring plate. The height of the stopcock was adjusted to half the universal support to prevent bubble formation. The solution was transferred to a 500 mL Schott flask and allowed to crosslink overnight in the precipitant solution, before being refrigerated. The capsules were washed with plenty of milli-Q water, approximately 600 mL in a one-liter beaker. They were then separated from the liquid using a strainer.This procedure was repeated as many times as necessary until translucent capsules were obtained. Finally, the capsules were stored in 500 mL Schott flasks and refrigerated.

[0092] Example 7. Preparation of microcapsules with chitosan 3% w / v, and acetic acid 5% v / v

[0093] Initially, 3 g of chitosan were added to a 250 ml Schott flask. To this mixture, 100 ml of milli Q water, taken with a 100 ml volumetric flask, were added, and 5 ml of acetic acid were added. Subsequently, the 250 ml Schott flask was placed on a magnetic plate and kept under constant stirring at 80°C until a viscous solution was obtained, which was then refrigerated. After 24 hours of standing, the solution was sonicated for 30 minutes. The solution was then transferred to a dropping pump at 4 rpm and allowed to precipitate over 1 M NaOH, then poured into another Schott flask. The solution was then washed with plenty of milli Q water and refrigerated in a Schott with milli Q water. The capsules obtained on the 1 M NaOH solution were transferred to a 500 ml Schott flask, adding a 5% W / V glutaraldehyde solution to be crosslinked by the solution and were stored refrigerated for 24 hours.The capsules were then washed with plenty of milli-Q water, approximately 600 ml in a one-liter beaker. They were separated from the liquid using a sieve, and this process was repeated until translucent capsules were obtained. The capsules were stored in 500 ml Schott flasks and then refrigerated.

[0094] Example 8. Preparation of microcapsules with 3% w / v chitosan, 5% v / v acetic acid, and lamella

[0095] Polymeric capsules were prepared using chitosan and nanoparticulate lamellae. Different percentages of lamellae were used: 50%, 30%, and 20%, with corresponding masses of 1.5 g, 0.9 g, and 0.6 g, respectively. The precipitation times were 14, 16, and 14 minutes, respectively.

[0096] The process began by adding 3 g of chitosan to a 250 mL Schott flask. To this solution were added 100 mL of ultra-purified water (milli Q) and 5 mL of acetic acid. The lamella mass was then added to the flask, followed by 25 mL of ultra-purified water to entrain the nanoparticles. The mixture was left on a magnetic hotplate with constant stirring at 80°C until a viscous solution formed. After this, it was allowed to cool gradually, refrigerating for 24 hours.

[0097] After 24 hours of standing, the solution was sonicated for 60 minutes. The solution was then passed through a drip pump at 4 rpm, allowing it to precipitate over 1 M NaOH. The solution was then washed with abundant ultra-purified water and stored under refrigeration in a glass bottle with ultra-purified water. The resulting capsules were transferred to a 500 mL glass bottle, including a 5% glutaraldehyde solution to cross-link the capsules, and stored and refrigerated for 24 hours.

[0098] Finally, the capsules were washed with approximately 600 mL of ultra-purified water in a one-liter beaker and separated from the liquid using a strainer. This procedure was repeated until translucent capsules were obtained. The resulting capsules were stored in 500 mL glass bottles and refrigerated.

[0099] Example 9. Preparation of microcapsules with 1% w / v chitosan, 2.5% w / v sodium alginate, and lamella

[0100] Polymeric capsules were prepared with different percentages of nanoparticulate lamellae, specifically 50%, 30%, and 20%. Different precipitation times were observed for each percentage: 14:00 minutes for 50%, 15:00 minutes for 30%, and 16:00 minutes for 20%.

[0101] First, an AlgNa solution was prepared. To do this, 2.5 g of AlgNa was added to a 250 mL Schott flask, followed by 100 mL of milli-Q water. The mixture was heated to 60°C on a hot plate with constant stirring until a viscous solution was obtained. This solution was refrigerated, and the corresponding percentage of flakes was then added, subjecting it to sonication for 2 hours with paddle stirring.

[0102] In parallel, a 1% W / V Qui solution was prepared. In another 250 mL Schott flask, 1.0 g of Qui was introduced with 100 mL of milliQ water. The Qui solution was placed on a hot plate at 80°C with constant stirring, and 1 mL of acetic acid was added. Subsequently, 3 g of CaCh were added and stirred until a viscous solution was obtained. After gradually cooling the solution, it was transferred to a 250 mL beaker. The capsules were precipitated using a pump at 4 rpm, pouring the 2.5% W / V AlgNa / 50% ammonium chloride solution onto 100 mL of the 1% W / V Qui solution (containing 1% V / V acetic acid and 3% W / V CaCh). The precipitating solution was left with the capsules for 3 hours to crosslink, on a stirring plate.

[0103] The resulting capsules were washed with approximately 600 mL of milliQ water in a one-liter beaker. They were separated from the liquid using a strainer, and the procedure was repeated until translucent capsules were obtained. The capsules were stored in 500 mL Schott flasks and refrigerated for 24 hours. Example 10. Method for removing arsenic from an aqueous solution

[0104] This example focuses on the application of the developed encapsulated materials for the removal of arsenic (As) from an aqueous solution. The studies were conducted with encapsulates containing 20 phr of flakes, as these showed the best removal results. Sorption kinetics were performed to determine the equilibrium time, i.e., the time at which maximum As removal is reached. The tests were conducted with 20 mL of a 10 mg L-1 solution. -1of As(V) with 0.01 M NaCl, adjusted to the optimum pH for As removal, and 4 g of the substrates under study. The data obtained from the sorption kinetics were adjusted to the kinetic mathematical models of PPO and PSO, the latter showing a better level of fit to the experimental data. This indicated that As(V) is removed mainly by the formation of bidentate complexes. The equilibrium time was generally found between 30 to 60 minutes, with the CMC / Alg 20% ​​encapsulated sample modified with HCl being the fastest to reach this state. It was observed that the materials treated with HCl showed a higher speed and capacity for As(V) removal, being 8 times faster and having a capacity of 2.5 times more than the other treatments. This behavior was maintained in all the polymer mixtures used, with a slight superiority for the flake samples treated with HCl and encapsulated with chitosan.Finally, As(V) removal tests were performed over a 24-hour period at a concentration of 1.0 ppm, closer to real-world conditions. Results showed that the encapsulates adsorbed 20 to 60% (200 to 600 ppb) of the As(V) concentration, with NaOH and NaBH4 treating the materials with the best removal rates. Column studies were also performed to analyze the hydraulic capacity of the materials and other parameters such as flow rate, pressure, and throughput. A 14-cm-high, 2.5-cm-diameter column was used, loaded with the selected materials between two layers of gravel. The system was fed with 3 L of a 10 ppm As(V) solution using a peristaltic pump with feed flow rates ranging from 5.4 to 160.8 mL-min-1. The results showed that the materials removed up to 100% of the As(V), reaching an equilibrium close to 70%.

Claims

CLAIMS 1. A filter material for the removal of heavy metals, comprising an iron material, CHARACTERIZED in that the iron material is composed of at least 50% a mixture of iron oxides, and where the iron material has a particle size of less than 300 pm.

2. The filter material according to claim 2, CHARACTERIZED in that the iron oxides are selected from the group consisting of: a- Fe2O3, [3-Fe2O3, FesO4, ZnFe2O4 and FeMnOs.

3. A filter material for removing heavy metals, comprising the filter material according to claim 1 or 2, characterized in that: said filter material is microencapsulated in one or more biodegradable polymers; wherein the one or more biodegradable polymers are selected from the group consisting of alginate, polyvinyl alcohol, carboxymethyl cellulose and chitosan; and wherein the iron material has a particle size of less than 100 pm.

4. The filter material according to claim 3, CHARACTERIZED in that the iron material has a mass of 1 to 50% of the total biodegradable polymer mass.

5. A method for obtaining the filter material according to claim 3 or 4, CHARACTERIZED in that it comprises the steps of: a) mixing a solution comprising one or more biodegradable polymers selected from the group consisting of alginate, polyvinyl alcohol, carboxymethyl cellulose and chitosan; with an iron material with a particle size of less than 100 pm and composed of at least 50% of a mixture of iron oxides; b) sonicating the biodegradable polymer solution and the iron material; c) adding the solution comprising one or more biodegradable polymers and the iron material dropwise to a precipitation solution to obtain microcapsules in the precipitation solution; d) stirring the precipitation solution with the microcapsules for a time greater than 3 hours to allow polymer crosslinking to occur; and e) washing the microcapsules with water.

6. The method according to claim 5, CHARACTERIZED in that the total amount of the one or more biodegradable polymers is between 1 and 8% w / v; 7. The method according to claim 6, CHARACTERIZED in that the one or more biodegradable polymers are selected from the group consisting of: 5% w / v polyvinyl alcohol plus 1.5% w / v sodium alginate; 2% w / v carboxymethyl cellulose plus 2% w / v sodium alginate; and 1% w / v chitosan plus 2.5% w / v sodium alginate.

8. The method according to claim 7, CHARACTERIZED in that the iron material is added at an amount between 1 and 50% of the mass of biodegradable polymer.

9. The method according to claim 5, CHARACTERIZED in that one or more of the one or more biodegradable polymers are part of the precipitation solution.

10. The method according to claim 5, CHARACTERIZED in that the precipitation solution comprises CaCh and an acid selected from the group consisting of HBO3 and acetic acid.

1. The method according to claim 10, CHARACTERIZED in that the CaCh is at a concentration between 2 and 4% w / v, the HBO3 is at a concentration between 1 and 3% w / v, and the acetic acid is at a concentration between 1 and 5% v / v.

12. A method for removing heavy metals using the filter material of any one of claims 1 to 4, comprising the steps of: a) passing a fluid contaminated with heavy metals through the filter material; b) recovering the fluid with a reduced concentration of heavy metals.

13. A filter device for the removal of heavy metals, CHARACTERIZED in that it comprises the filter material of any of claims 1 to 4.

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