COMPOSITE OF CHITOSAN, TANNIC ACID AND SODIUM DODECYL SULFATE FOR ADSORPTION OF METHYLENE BLUE

Description

1 / 11 COMPOSITE OF CHITOSAN, TANNIC ACID AND SODIUM DODECYL SULFATE FOR ADSORPTION OF METHYLENE BLUE TECHNICAL SECTOR OF THE INVENTION

[001] The invention patent described herein has as its field of application the treatment of domestic, commercial, and industrial effluents. It is known that technologies for effluent purification need innovation, as it is still possible to find concentrations of materials harmful to humans and animals in effluents. Dyes stand out among the potential contaminants due to the difficulty of their removal from the environment, as they represent serious harm to health and cause damage to the environment. Thus, a composite based on chitosan (CS) and tannic acid (AT) gelled in a sodium dodecyl sulfate (SDS) solution emerges as a low-cost and highly efficient alternative for the removal of methylene blue dye from effluents. The resulting bioadsorbent material (CS-AT / SDS) can be kept in aqueous solution (wet adsorbent) or undergo a drying process (dry adsorbent) for later use in adsorption processes.The technical sector includes the field of chemistry, with an emphasis on environmental chemistry. DESCRIPTION OF THE STATE OF THE ART

[002] Aquatic ecosystems such as ponds and rivers are currently threatened due to constant contamination. Inefficient treatment of industrial effluents can improperly release toxic substances into water bodies. Attention is drawn to the improper release of dyes from the textile, paper, or food industries, for example (HOSLETT et al., 2020).

[003] Some dyes are not biodegradable and accumulate in the body causing diseases that can lead to death (DESHMUKH et al., 2022). In addition, these are responsible for genetic alterations that can lead to cancer (DAS; PAL, 2016).

[004] For the removal of dyes and other pollutants from effluents, techniques such as coagulation, ion exchange, precipitation, membrane separation, oxidation, electrochemistry and biodegradation are used (DAS; PAL, 2016; Petition 870260034789, dated 04 / 14 / 2026, page 4 / 14 2 / 11 (JAMALI; AKBARI, 2021). These techniques may require specific and expensive equipment; complex operational methodologies; low effectiveness in removing certain types of contaminants; excessive energy consumption; the need for qualified operators in treatment plants; and the production of substances toxic to the environment in intermediate stages of the process (CHATTERJEE; CHATTERJEE; WOO, 2010; SHAIKH et al., 2022; WANG et al., 2022). Thus, the adsorption technique is used as an efficient and low-cost alternative for removing pollutants from wastewater (DAS; PAL, 2016).

[005] Adsorption allows for the diversification of materials that make up the adsorbent, increasing the affinity with different molecules. For example, it is possible to use clay, biomass, zeolites, silica gel, carbon nanotubes, alumina, metal oxides, and biopolymers in the composition of adsorbents (BISWAS; PAL, 2021; JAMALI; AKBARI, 2021; KRÁLIK, 2014; ROCHA et al., 2021).

[006] In particular, chitosan stands out among biopolymers for being biodegradable, non-toxic, a cationic polymer (CHATTERJEE et al., 2018), and allowing structural modification from reactive hydroxyl and amino group sites (GONSALVES; et al., 2011). Also, chitosan is a polysaccharide formed by the combination of glucosamine units, being derived from chitin (LI et al., 2018b).

[007] Munim and colleagues (2020) describe the formation of an adsorbent in a chitosan matrix for wastewater treatment. For this purpose, a spherical composite of chitosan and cellulose showed excellent performance in removing metallic contaminants. The work indicated that chitosan increased the adsorption capacity of metallic ions. In another study, chitosan was grafted onto polyethyleneimine to form an adsorbent that removes pharmaceuticals (LU et al., 2020). The authors justified the greater adsorption due to the availability of more reactive groups. Petition 870260034789, dated 04 / 14 / 2026, page 5 / 14 3 / 11

[008] Regarding the possibility of structural modification of chitosan, the organic molecule tannic acid plays an important role as a crosslinking agent. By interacting with the amino group of chitosan, tannic acid inserts more reactive sites originating from phenolic hydroxyls, which increases the adsorption capacity of the adsorbent and confers greater mechanical resistance to chitosan (MALLAKPOUR; RADFAR; FEIZ, 2022).

[009] Tannic acid is a natural polyphenol found in plant bark and has the pyrogallol group as its reactive site (LIU et al., 2022). For an adsorbent system in a chitosan matrix, the phenolic hydroxyl groups and aromatic nuclei increase the possibilities of interaction with the desired analyte, confer greater stability in acidic media, increase mechanical resistance, and it is a reagent easily obtained in nature (FU et al., 2021; MALLAKPOUR; RADFAR; FEIZ, 2023).

[010] Polyphenolic hydroxyl groups are responsible for enabling the covalent crosslinking process between biopolymeric chains (KROGSGAARD; ANDERSEN; BIRKEDAL, 2014). In this sense, tannic acid is used to form ordered intermolecular interactions with chitosan (LI et al., 2018a). This interaction occurs via Schiff base reaction or Michael addition (MALLAKPOUR; RADFAR; FEIZ, 2022). When interacting, tannic acid improves the properties of chitosan, since pure chitosan is soluble in acidic media, representing a limiting factor for chitosan to act in pure form in solutions with acidic pH (MALLAKPOUR; RADFAR; FEIZ, 2023).

[011] Therefore, the improvement of the mechanical properties of chitosan is obtained in the formation of composites from the insertion of tannic acid. The positive advances in properties are a result of the action of tannic acid as a crosslinking agent of chitosan by diversifying the interactions between the polymeric layers (ROY et al., 2021). In the literature, Wang and colleagues (2020) reported the formation of a chitosan composite using tannic acid in the creation of an alternative adsorbent composite. The authors described that the presence of the polyphenolic compound increased the adsorption capacity of contaminants in wastewater treatment systems. Petition 870260034789, dated 04 / 14 / 2026, page 6 / 14 4 / 11

[012] Also, the modification of chitosan spheres is possible through the use of sodium dodecyl sulfate (SDS) (DAS; PAL, 2016). Pure chitosan has the disadvantage of being hydrophilic, but SDS is an anionic surfactant that, in the formation of composites, confers a greater hydrophobic character to chitosan-based biomaterials. This is possible due to the presence of a long alkyl group in the surfactant structure, which increases the interaction with hydrophobic molecules, mainly organic substances such as dyes (AMRI; HUSSEINSYAH; HUSSIN, 2013).

[013] Another advantage of using SDS in composites lies in the fact that the surfactant is used to form spherical adsorbent gels. In this case, SDS acts as a gelling agent due to the formation of a gel layer at the outer interface of the chitosan sphere (CHATTERJEE; CHATTERJEE; WOO, 2010).

[014] The gelation of chitosan spheres by the action of SDS serves to form efficient adsorbents for the removal of the cationic dye methylene blue from aqueous solution. It is known that pure chitosan has a low adsorption capacity and, in addition, when protonated in an acidic medium it acquires a positive charge. This limitation is overcome by reacting the biopolymer with the surfactant SDS (CHATTERJEE et al., 2011).

[015] Studies by Chatterjee et al. (2022) show that chitosan capsules formed after dripping in SDS solution had a high capacity for dye adsorption due to the formation of reactive heterogeneous sites. Furthermore, it demonstrated that the surfactant improves the composition of bioadsorbents, as it allows the use of gelled chitosan in the removal of contaminants with the same charge. This is possible due to the reduction of electronic repulsion due to the inversion of the net charge on the chitosan surface (PAL; PAL, 2017).

[016] Therefore, the limitations of chitosan in acting in acidic media and low adsorption capacity when pure are overcome by the formation of a composite from interactions with tannic acid and sodium dodecyl sulfate. These Petition 870260034789, dated 04 / 14 / 2026, page 7 / 14 5 / 11 interactions allows the creation of a low-cost, high-efficiency alternative composite for wastewater treatment.

[017] AMRI, F.; HUSSEINSYAH, S.; HUSSIN, K. Effect of sodium dodecyl sulfate on mechanical and thermal properties of polypropylene / chitosan composites. Journal of Thermoplastic Composite Materials, v. 26, n. 7, p. 878-892, 2013. BADAWI, M. A.; NEGM, N. A.; ABOU KANA, M. T. H.; HEFNI, H. H.; ABDEL MONEEM, M. M. Adsorption of aluminum and lead from wastewater by chitosan-tannic acid modified biopolymers: Isotherms, kinetics, thermodynamics and process mechanism. International Journal of Biological acromolecules, v. 99, p. 465-476, 2017. BISWAS, S.; PAL, A. Application of biopolymers as a new age sustainable material for surfactant adsorption: A brief review. arbohydrate Polymer Technologies and Applications, v. 2, 2021.

[018] CHATTERJEE, S.; CHATTERJEE, T.; LIM, S. R.; WOO, S. H. Adsorption of a cationic dye, methylene blue, on to chitosan hydrogel beads generated by anionic surfactant gelation. Environmental Technology, v. 32, n. 13, p. 15031514, 2011. CHATTERJEE, S.; CHATTERJEE, T.; WOO, S. H. A new type of chitosan hydrogel sorbent generated by anionic surfactant gelation.

[019] Bioresource Technology, v. 101, n. 11, p. 3853-3858, 2010. CHATTERJEE, S.; OHEMENG-BOAHEN, G.; SEWU, D. D.; OSEI, B. A.; WOO, S. H. Improved adsorption of Congo red from aqueous solution using alkalitreated goethite impregnated chitosan hydrogel capsule. Journal of Environmental Chemical Engineering, v. 10, n. 5, 2022. CHATTERJEE, S.; TRAN, H. N.; GODFRED, O. B.; WOO, S. H. Supersorption Capacity of Anionic Dye by Newer Chitosan Hydrogel Capsules via Green Surfactant Exchange Method. ACS Sustainable Chemistry and Engineering, v. 6, n. 3, p. 36043614, 2018. DAS, D.; PAL, A. Adsolubilization phenomenon perceived in chitosan beads leading to a fast and enhanced malachite green removal.

[020] Chemical Engineering Journal, v. 290, p. 371-380, 2016. DESHMUKH, S. M.; PATIL, S. S.; BABAR, S. B.; ALSHEHRI, S.; GHONEIM, M. M.; TAMBOLI, A. M.; LAM, N. H.; TRUONG, N. T. N.; KIM, C. D.; TAMBOLI, M. S.; KHETRE, SM; BAMANE, SR TiO2-SnO2 Nanocomposites for Photocatalytic Environmental Remediation under UV-Light. Metals, v. 12, n. 5,. Petition 870260034789, dated 04 / 14 / 2026, p. 8 / 14 6 / 11 pp. 1-12, 2022.

[021] FU, Y.; SUN, Y.; ZHENG, Y.; JIANG, J.; YANG, C.; WANG, J.; HU, J. Novel functional magnetic-mesoporous network polymer nanoparticle for fast Hg(II) adsorption and efficient sequential reuse as a catalyst. Separation and Purification Technology, v. 259, n. October 2020, 2021.

[022] GONSALVES;, A. de A.; ARAÚJO, CRM; SOARES, NA; GOULART, MOF; ABREU, FC de. DIFFERENT STRATEGIES FOR CHITOSAN CROSSLINKING. Quim. Nova, v. 34, n. 7, p. 1215-1223, 2011.

[023] HOSLETT, J.; GHAZAL, H.; MOHAMAD, N.; JOUHARA, H. Removal of methylene blue from aqueous solutions by biochar prepared from the pyrolysis of mixed municipal discarded material. Science of the Total Environment, v. 714, 2020. JAMALI, M.; AKBARI, A. Facile fabrication of magnetic chitosan hydrogel beads and modified by interfacial polymerization method and study of adsorption of cationic / anionic dyes from aqueous solution. Journal of Environmental Chemical Engineering, v. 9, n. 3, 2021. KRÁLIK, M. Adsorption, chemisorption, and catalysis. Chemical Papers, v. 68, n. 12, p. 1625-1638, 2014.

[024] KROGSGAARD, M.; ANDERSEN, A.; BIRKEDAL, H. Gels and threads: Mussel-inspired one-pot route to advanced responsive materials. Chemical Communications, v. 50, n. 87, p. 13278-13281,2014.

[025] LI, N.; YANG, X.; LIU, W.; XI, G.; WANG, M.; LIANG, B.; MA, Z.; FENG, Y.; CHEN, H.; SHI, C. Tannic Acid Cross-linked Polysaccharide-Based Multifunctional Hemostatic Microparticles for the Regulation of Rapid Wound Healing. Macromolecular Bioscience, v. 18, n. 11, p. 1-16, 2018a. LI, Q.; XU, B.; ZHUANG, L.; XU, X.; WANG, G.; ZHANG, X.; CHEN, J.; TANG, Y. Preparation, characterization, adsorption kinetics and thermodynamics of chitosan adsorbent grafted with a hyperbranched polymer designed for Cr(VI) removal. Cellulose, v. 25, n. 6, p. 3471-3486, 2018b. Petição 870260034789, de 14 / 04 / 2026, pág. 9 / 14 7 / 11

[026] LIU, S.; JIANG, N.; CHI, Y.; PENG, Q.; DAI, G.; QIAN, L.; XU, K.; ZHONG, W.; YUE, W. Injectable and Self-Healing Hydrogel Based on Chitosan-Tannic Acid and Oxidized Hyaluronic Acid for Wound Healing. ACS Biomaterials Science and Engineering, v. 8, n. 9, p. 3754-3764, 2022. LU, Y.; WANG, Z.; OUYANG, X. kun; JI, C.; LIU, Y.; HUANG, F.; YANG, L. Y. Fabrication of crosslinked chitosan beads grafted by polyethylenimine for efficient adsorption of diclofenac sodium from water. International Journal of Biological Macromolecules, v. 145, p. 1180-1188, 2020. MALLAKPOUR, S.; RADFAR, Z.; FEIZ, M. Optimization of chitosan / tannic acid@ ZnFe layered double hydroxide bionanocomposite film for removal of reactive blue 4 using a response surface methodology. International Journal of Biological Macromolecules, v. 209, n. April, p. 747-762, 2022. MALLAKPOUR, S.; RADFAR, Z.; FEIZ, M.Chitosan / tannic acid / ZnFe layered double hydroxides and mixed metal oxides nanocomposite for the adsorption of reactive dyes. Carbohydrate Polymers, v. 305, n. October 2022, 2023. MUNIM, S. A.; SADDIQUE, M. T.; RAZA, Z. A.; MAJEED, M. I. Fabrication of cellulosemediated chitosan adsorbent beads and their surface chemical characterization. Polymer Bulletin, v. 77, n. 1, p. 183-196, 2020. PAL, P.; PAL, A. Surfactantmodified chitosan beads for cadmium ion adsorption. International Journal of Biological Macromolecules, v. 104, p. 1548-1555, 2017. ROCHA, L. S.; SOUSA, É. M. L.; PEREIRA, D.; GIL, M. V.; OTERO-IRURUETA, G.; HORTIGÜELA GALLO, M. J.; OTERO, M.; ESTEVES, V. I.; CALISTO, V. Sustainable and recoverable waste-based magnetic nanocomposites used for the removal of pharmaceuticals from wastewater. Chemical Engineering Journal, v. 426, n. April, 2021. ROY, S.; ZHAI, L.; KIM, H. C.; PHAM, D. H.; ALROBEI, H.; KIM, J.Tannic-acid-cross-linked and TiO2-nanoparticlereinforced chitosan-based nanocomposite film. Polymers, v. 13, n. 2, p. 1-18, 2021. SHAIKH, W. A.; KUMAR, A.; CHAKRABORTY, S.; ISLAM, R. U.; BHATTACHARYA, T.; BISWAS, J. K. Biochar-based nanocomposite from waste tea leaf for toxic dye removal: From facile fabrication to functional fitness. Petição 870260034789, de 14 / 04 / 2026, pág. 10 / 14 8 / 11

[027] Chemosphere, v. 291, n. November 2021, 2022. WANG, Q.; ZHU, S.; XI, C.; ZHANG, F. A Review: Adsorption and Removal of Heavy Metals Based on Polyamide-amines Composites. Frontiers in Chemistry, v. 10, n. March, p. 115, 2022. WANG, Z.; LIU, Z.; YE, T.; WANG, Y.; ZHOU, L. Removal of uranyl ions from aqueous media by tannic acid-chitosan hydrothermal carbon: equilibria, kinetics and thermodynamics. Journal of Radioanalytical and Nuclear Chemistry, v. 326, n. 3, p. 1843-1852, 2020. SOLUÇÃO PROPOSTA PELA INVENÇÃO

[028] To produce a composite formed by chitosan, tannic acid and sodium dodecyl sulfate. An alternative adsorbent that improves stability in acidic media and increases the adsorption capacity of chitosan, contributing to wastewater treatment using a highly efficient and low-cost adsorbent, through the use of renewable, non-toxic and readily available materials. NOVELTY OF THE INVENTION

[029] The invention consists of a composite formed by chitosan and tannic acid through gelation in surfactant solution to obtain a bioadsorbent. The adsorbent material showed stability in acidic medium, high adsorption capacity, in addition to having low acquisition cost, being easy to obtain, simple to use and being efficient for the treatment of effluents, especially for the removal of cationic dye contained in aqueous solution. LIST OF FIGURES AND GRAPHIC REPRESENTATION

[030] FIGURE 1 - Presents an illustration of the formation of the chitosan, tannic acid and sodium dodecyl sulfate composite.

[031] FIGURE 2 - Shows the infrared spectrum (FTIR) of the chitosan, tannic acid and sodium dodecyl sulfate composite.

[032] FIGURE 3 - Shows the adsorption capacity for each variation of the adsorbent system, using methylene blue as adsorbate.

[033] FIGURE 1 shows the steps in the formation of the CS-AT / SDS composite formed by chitosan (CS), tannic acid (AT) and sodium dodecyl sulfate (SDS). Petition 870260034789, dated 04 / 14 / 2026, page 11 / 14 9 / 11

[034] The chitosan-tannic acid suspension (1) is dropped into an aqueous SDS solution (2). A distance of 10 cm is maintained between the biopolymer droplet that is formed at the syringe nozzle and the surface of the SDS solution. After washing the CS-AT / SDS spheres with distilled water three times, the composite (3) is ready for use. Furthermore, the adsorption capacity of the composite was tested in dry form (4). For this, the spheres were kept in a vacuum desiccator for 48 h without heating.

[035] FIGURE 2 shows the infrared spectrum of the chitosan, tannic acid, and sodium dodecyl sulfate composite. A stretching band was observed at 1531 cm-1, indicative of the presence of an NO linkage, as also observed by Badawi et al. (2017). The presence of the NO linkage is important to determine the effective interaction between the amino group of chitosan and the phenolic hydroxyl group of tannic acid. Another important band is the asymmetric stretching vibration attributed to the -CO-S- interaction that occurred at 1467 cm-1. This vibration determines the presence of SDS in the chitosan biopolymer structure (CHATTERJEE et al., 2018).

[036] FIGURE 3 shows the batch adsorption test results describing the adsorption capacity results for the composites formed in wet and dry form. The CS-AT / SDS composite interacted with the cationic dye methylene blue at different concentrations (100, 500 and 1000 mg / L). The highest adsorption capacity of wet CS-AT / SDS found was 109.57 mg / g, when using dye at a concentration of 500 mg / L. Also, the CS-AT / SDS composite in dry form adsorbed the dye at the same concentrations of 100, 500 and 1000 mg / L. It was observed that the highest adsorption capacity found (262.76 mg / g) was for the adsorbent in contact with methylene blue at 1000 mg / g. Comparing the best results between the wet and dry forms, the dry CS-AT / SDS composite showed the highest adsorption capacity for methylene blue dye. Petition 870260034789, dated 04 / 14 / 2026, page 12 / 14 10 / 11 DESCRIPTION OF THE INVENTION

[037] The formation of the chitosan, tannic acid and sodium dodecyl sulfate composite occurs in four steps (Figure 1).

[038] To form the composite, first prepare the chitosan solution (1% w / v) by dissolving the biopolymer in 5 mL of 2% v / v acetic acid solution. Keep this solution under magnetic stirring for 12 h.

[039] Also, prepare an aqueous solution of tannic acid (1% w / v) by dissolving tannic acid in 5 mL of distilled water.

[040] In the chitosan solution that is under continuous stirring, the tannic acid solution must be added. A ratio of 30% by volume of tannic acid solution to chitosan solution must be maintained. Keep the mixture under stirring for 30 min to form a suspension (1).

[041] Drop the formed biopolymer suspension into 100 mL of aqueous sodium dodecyl sulfate solution at 5 g / L (2). Fix the distance of 10 cm between the formed biopolymer drop on the syringe tip and the surface of the SDS solution. The formed spheres should be left to stand for 12 h, then washed three times with distilled water.

[042] After washing the spheres, it is possible to use them in a batch adsorption process. In this case, the spheres are called wet (3).

[043] Also, the spheres were tested for adsorption in dry form. In this case, the spheres after washing are dried in a vacuum desiccator for 48 h. After drying, the composite is ready for use (4). INDUSTRIAL APPLICATION OF THE INVENTION

[044] The formation of the composite that is the subject of this patent belongs to the field of chemistry, with an emphasis on environmental chemistry for use in wastewater treatment. A composite has been developed that acts in the purification of domestic, commercial, and industrial wastewater. Thus, there is a proposal to improve public health through the environmental protection of rivers and lakes, due to the correct treatment of effluents discharged into these water bodies. The composite can be used in water and sewage treatment plants because it is formed from easily obtainable, non-toxic components and contains natural and biodegradable substances. The resulting adsorbent stands out as an efficient agent in the treatment of water bodies when used Petition 870260034789, dated 04 / 14 / 2026, page 13 / 14 11 / 11 is a non-complex adsorption methodology, with low implementation costs, that guarantees the adequate removal of contaminants present in wastewater. Another important advantage of the composite generated for water and sewage treatment plants lies in the fact that the developed adsorbent material can be easily removed from the medium after use through a simple filtration process. Petition 870260034789, dated 04 / 14 / 2026, page 14 / 14

Claims

1 / 2 CLAIMS 1. A composite of chitosan, tannic acid and sodium dodecyl sulfate for methylene blue adsorption, characterized by containing chitosan solution (1% - 2% w / v); 5 mL of acetic acid solution (2% - 5% v / v); aqueous tannic acid solution (1% - 2% w / v); 5 mL of distilled water; sodium dodecyl sulfate (4.0 - 5.0 g / L) 2. Process for obtaining a chitosan, tannic acid, and sodium dodecyl sulfate composite for methylene blue adsorption, according to claim 1, characterized by first preparing a chitosan solution (1% w / v) by dissolving the biopolymer in 5 mL of acetic acid solution (2% v / v), maintaining this solution under magnetic stirring for 12 h, followed by preparing an aqueous solution of tannic acid (1% w / v) by dissolving tannic acid in 5 mL of distilled water, followed by adding the tannic acid solution to the chitosan solution, maintaining a 30% volume ratio of tannic acid solution to chitosan solution, followed by 30 minutes of stirring the mixture to form a suspension which is subsequently dropped into 100 mL of aqueous sodium dodecyl sulfate solution (5 g / L), fixing a distance of 10 cm between the biopolymer drop formed at the syringe nozzle and the surface of the solution. SDS,followed by resting the formed spheres for 12 hours, after which they are washed three times with distilled water, followed by drying in a vacuum desiccator for 48 hours.

3. A chitosan, tannic acid, and sodium dodecyl sulfate composite for methylene blue adsorption, according to claim 1, characterized by an adsorbent containing chitosan polysaccharide and a tannin-type polyphenol.

4. A chitosan, tannic acid, and sodium dodecyl sulfate composite for methylene blue adsorption, according to claim 1, characterized by dripping the chitosan and tannic acid polymer suspension into an aqueous solution of sodium dodecyl sulfate.

5. A composite of chitosan, tannic acid, and sodium dodecyl sulfate for methylene blue adsorption, according to claim 1, Petition 870250060292, dated 07 / 15 / 2025, page 19 / 21 2 / 2, characterized by an anionic surfactant promoting the gelation of spheres composed of chitosan and tannic acid.

6. A composite of chitosan, tannic acid, and sodium dodecyl sulfate for methylene blue adsorption, according to claim 1, characterized by being reusable in different adsorption and desorption cycles.

7. A chitosan, tannic acid, and sodium dodecyl sulfate composite for methylene blue adsorption, according to claim 1, characterized by allowing the use of the composite in wet form (spheres kept at rest in aqueous solution) or in dry form (composite dried in a vacuum desiccator, at room temperature, by lyophilization, or in an oven).

8. A composite of chitosan, tannic acid, and sodium dodecyl sulfate for the adsorption of methylene blue, according to claim 1, characterized by its ability to act in the purification of domestic, commercial, or industrial wastewater.

9. Composite of chitosan, tannic acid and sodium dodecyl sulfate for adsorption of methylene blue, according to claim 1, characterized by removing dyes, preferably methylene blue, from effluents. Petition 870250060292, dated 07 / 15 / 2025, pp. 20 / 21

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