Materials for use in chromium removal and ammonia reduction agents for chromium-containing collagen solutions

Abstract

This invention belongs to the field of solid hazardous waste treatment and resource utilization. Specifically, it discloses a method for preparing and applying a chromium-removing and ammonia-reducing agent for a chromium-containing collagen solution extracted from waste leather scraps. The chromium-removing and ammonia-reducing agent comprises a chromium ion replacement material, an electrostatic adsorption material, an ammonia-reducing material, a magnetic material, and a coating material. The chromium ion replacement material is prepared by grafting silica with a silane coupling agent and malonic acid and citric acid. The electrostatic adsorption material is obtained by modifying inorganic magnesium silicate materials. The ammonia-reducing material is obtained by synthesizing zeolite and modifying zeolite. The magnetic material is prepared by using Fe... 2+ Fe 3+ The raw materials are synthesized and prepared; the coating material is an organic polymer material; the coating material is obtained by coating chromium ion replacement material, electrostatic adsorption material, ammonia-reducing material, and magnetic material together through a process to obtain a chromium removal and ammonia-reducing agent. This invention has the advantages of simple process, low cost, thorough chromium removal, significant ammonia reduction, and suitability for industrial application.

Description

[0001] This invention is a divisional application of invention patent 2023107819997, which was filed on June 29, 2023. Technical Field

[0002] This invention belongs to the field of solid hazardous waste treatment and resource utilization, specifically relating to the preparation and application method of a chromium removal and ammonia reduction agent for a chromium-containing collagen solution extracted from waste leather scraps. Background Technology

[0003] In the leather industry, chrome tanning remains the primary tanning method due to its superior overall performance. Statistics show that processing one ton of raw hide generates 40%–45% solid waste, with my country producing approximately one million tons of chromium-containing waste hides annually. This waste, containing the heavy metal chromium, is classified as hazardous waste by the state, severely polluting the environment and hindering the sustainable development of the leather industry.

[0004] Chromium-containing waste leather scraps contain over 85% collagen, which is an important resource. Therefore, the resource utilization of collagen from chromium-containing waste leather scraps has significant social and economic implications. Leather scraps contain 2%–4% chromium. The application of chromium removal agents in chromium-containing collagen solutions involves the chelation of carboxyl, hydroxyl, and amino groups in the collagen of leather. Therefore, how to remove Cr(III) from leather scraps while maintaining a high collagen recovery rate has become a research hotspot for scientists. Several methods have been summarized to date: alkaline method, acid method, oxidation method, enzymatic method, and mixed method.

[0005] The principle of chromium removal by alkaline method is the free OH groups. - The chromium enters the inner sphere of the chromium complex, replacing collagen chelation to form Cr(OH)3 precipitate, which is then removed by pressure filtration using a plate filter press. This method can remove most of the chromium, but a small amount of chromium remains in the collagen solution, with a chromium content of 10-100 mg / L. Zhao Jiahua et al. (Exploration of Chromium Removal from Waste Leather Flakes and Compound Alkali Method [J]. Leather Science and Engineering, Vol.26, No.5 Oct.2016:68-70) extracted collagen solutions with a chromium content of 25-90 ppm. The industrial protein powder obtained after drying had a chromium content of 100-200 mg / Kg, exceeding the national standard of ≤50 mg / Kg, and failing to meet the actual market demand.

[0006] The principle of acid removal of chromium is: under acidic conditions, COO2... -The conversion to COOH promotes the dissociation of the chelate formed between chromium and collagen, while the acid radical ions undergo a complexation reaction with chromium, thereby achieving the purpose of chromium removal. Acid treatment has the advantage of high collagen extraction rate, but its disadvantages include excessive decomposition of collagen molecules, small molecular weight of the obtained product, and incomplete chromium separation. Wang Xi'an et al. (Study on phosphoric acid removal of chromium from wet blue leather [J]. Western Leather, Vol. 31 No. 19 Oct. 2009: 20-24) obtained a collagen solution with a chromium content of several hundred ppm using the acid method. However, tryptophan, serine, tyrosine, and other amino acids in the hydrolysate are destroyed. In large-scale industrial production, the acid treatment method is difficult to implement due to equipment limitations.

[0007] The principle of chromium removal by oxidation is as follows: An oxidizing agent converts trivalent chromium in chromium-containing leather scraps to hexavalent chromium, thus eliminating its tanning properties. After rinsing and filtration, the collagen and chromium phases are separated, achieving the purpose of chromium removal. Sun Danhong (Research on Oxidative Method for Chromium Removal from Chromium-Containing Waste Leather Scraps [J]. Leather Science and Engineering, Vol. 12, No. 3 Jun.2002:31-36) reported that the chromium removal rate using the oxidation process is over 90%. The advantages of the oxidation method are fast chromium removal speed, minimal damage to collagen structure, bright color, and large molecular weight of the obtained collagen. Its disadvantages include the generation of highly toxic hexavalent chromium during production, requiring further treatment, increasing costs and process difficulty.

[0008] The principle of enzymatic chromium removal is that, under the action of alkaline protease, the peptide bonds in the collagen fibers of chromium-containing leather scraps are hydrolyzed, dissolving in water. Chromium then reacts with OH-. - The reaction precipitates Cr(OH)3. Enzymatic methods offer advantages such as high specificity, short reaction time, mild conditions, no equipment corrosion, and minimal protein damage, making them a valuable and efficient technology for the clean recovery of collagen. Zhou Wen et al. (Preparation of High Molecular Weight Products by Crosslinking Protein Isolated from the Enzymatic Processing of Chromium Containing Collagenous Waste: I. Extraction of Gelatin[J]. Leather Science and Engineering, Vol. 15, No. 2 Apr. 2005:3-7) conducted corresponding research using enzymatic methods. While enzymatic methods offer advantages such as mild conditions and environmental friendliness, they suffer from low chromium removal and collagen extraction rates. Furthermore, the theoretical understanding of the enzyme's action sites on collagen fiber molecules and the control of the enzymatic hydrolysis endpoint remains unclear, thus limiting the application of enzymatic processes.

[0009] There are also multiple methods used in combination, such as acid-base method (Zhao Shengzong et al., Optimization of CaO dechromium removal in acid-base combined treatment of chromium leather scraps [J], Leather Science and Engineering, 30(1):17-22 Feb.2020), alkali-enzyme method (Qiang Xihuai et al., Process method for extracting collagen from waste chromium leather scraps by alkali-enzyme combination method [J]. China Leather, Vol. 40 No.1 Jan.2011), acid-base oxidation method, etc., but the chromium content of the collagen solution obtained is generally greater than 20ppm, and there are other limitations, such as high cost, complex operation process, or existing equipment that cannot be industrialized, making it difficult to truly achieve industrialization.

[0010] Among the various methods mentioned above, the alkaline method is widely used in industry due to its simple process, thorough dechromium removal, and high protein extraction rate. However, the alkaline method also has many problems, such as the small molecular weight of hydrolyzed protein and the generation of a certain amount of ammonia. The generation of ammonia will affect the quality of protein and reduce the freshness of protein powder. How to reduce the ammonia content in the extract and improve the freshness of the product has become an urgent issue for enterprises. Current research projects in this area are discussed in detail below.

[0011] For chromium removal technology to be industrialized, it needs to meet the following requirements: first, it must be able to deeply remove chromium from collagen solutions; second, the chromium removal and ammonia-reducing agent must be able to be quickly separated from the solution; and third, it must be easy to operate and conducive to enterprise production. Summary of the Invention

[0012] While alkaline methods remove chromium relatively thoroughly, a small amount of chromium in the resulting collagen solution remains chelated with carboxyl, hydroxyl, and amino groups in the collagen; a small amount of Cr(OH)3 is converted into colloids; and some chromium reacts with hydroxyl groups to form polyhydroxy chromium complexes. These three types of chromium-containing substances cannot be removed by ordinary precipitation methods. The purpose of this invention is to prepare a chromium-removing and ammonia-reducing agent that removes these three types of chromium-containing substances from collagen solutions that are difficult to remove by precipitation and filtration, and also enables rapid solid-liquid separation. The collagen solution obtained by alkaline hydrolysis contains a certain amount of ammonia, which reduces the freshness of the protein powder and thus affects its quality. The product of this invention can also remove ammonia from the solution, improving product freshness and protein powder quality.

[0013] To address the issue that a small amount of chromium in collagen solution remains chelated with collagen and is difficult to remove, the technical solution of this invention is as follows: based on the principle that ligands with strong coordination ability can replace ligands with weak coordination ability, a stronger ligand is found to displace chromium from the coordination of collagen, and then removed by precipitation.

[0014] For solutions containing a small amount of Cr(OH)3 colloids and a small amount of polyhydroxy chromium complex ions, the technical solution is to use an adsorbent with opposite charges to remove them by utilizing the basic physical principle of electrostatic adsorption, based on the characteristic that colloidal particles and polyhydroxy chromium complex ions are charged.

[0015] The technical solution to reduce the presence of ammonia in collagen solutions, which affects the quality of protein powder, involves first adjusting the pH to make the solution neutral or weakly acidic, thus converting it into ammonium ions, which are then removed through exchange with ions in inorganic materials.

[0016] Improving the efficiency of solid-liquid separation is crucial in actual production. The settling velocity of inorganic particles in solution is directly related to the particle size: larger particles settle faster, which is more conducive to solid-liquid separation. Technical solutions include: first, using a coating material to encapsulate several materials together, increasing particle size and improving solid-liquid separation efficiency; second, utilizing magnetic properties by adding a magnetic material to achieve rapid separation from the solution via a magnet.

[0017] Invention Concept

[0018] (1) Cr derived from practice 3+ The ligand strength sequence is: oxalate > citrate > malonate > succinate > phthalate > acetate > collagen carboxylate. Citrate's strong coordinating ability can displace chromium chelated by collagen; however, citrate's large molecular weight introduces steric hindrance, affecting its penetration into leather tissue and thus its chromium removal efficiency. To compensate for this, malonate is added to the system. It has a small molecular weight, low steric hindrance, and strong permeability in leather tissue. The synergistic effect of malonate and citrate in chromium removal makes the chromium coordination displacement more thorough.

[0019] (2) Since citrate and malonate coordinate with chromium to form soluble complex ions that cannot be precipitated, the abundant hydroxyl active groups on the surface of nano silica are used to graft citrate and malonate onto its surface through chemical methods to prepare chromium ion replacement agent. Chromium is removed by means of the sedimentation effect of nano silica in solution.

[0020] (3) In the powders of kaolinite, montmorillonite, diatomite, and magnesium silicate, the high valence state of aluminum silicate ions results in a charged particle surface in aqueous solution, exhibiting electrostatic attraction. Therefore, they can adsorb colloids and polyhydroxy chromium complex ions. The powders are immersed in dilute acid, stirred, soaked, and washed to thin and reduce the original layered structure, exposing the Al and Si active sites on their surface, significantly increasing the electrostatic attraction. After drying and calcination, electrostatic adsorption materials are obtained. Grafting EDTA onto the surface of the electrostatic adsorbent further enhances its removal of chromium ions.

[0021] (4) To address the problem of a certain amount of ammonia in collagen solution affecting the freshness of protein powder, zeolite is synthesized and activated to obtain an ammonia removal material. Zeolite has a silicon (aluminum) oxygen tetrahedral crystal structure. The zeolite framework contains excess negative charge. To maintain electroneutrality, metal cations are needed to neutralize the negative charge. However, metal cations are unstable in the zeolite structure and are easily replaced by cations in the solution. The pores of zeolite are generally 300-1000 pm, and the diameter of ammonium ions is 286 pm, which can directly enter the pores. Larger ions cannot enter, thus selectively replacing ammonium ions to achieve the purpose of ammonia removal. Activation treatment of zeolite can significantly improve the ammonia removal rate.

[0022] (5) Because the nano-silica particles are small and have abundant hydroxyl groups on their surface, they settle slowly in the solution and have a long precipitation time. The solution to this problem is to use a magnet to achieve rapid separation of solid magnetic materials from the solution; use a coating material to coat the magnetic material, chromium ion replacement material, electrostatic adsorption material and ammonia removal material together. In this way, on the one hand, the magnet can achieve rapid solid-liquid separation, and on the other hand, the particles become larger when the several substances are coated together, which is conducive to rapid sedimentation.

[0023] (6) A chromium removal and ammonia reduction agent for chromium-containing collagen solution is prepared by means of the above invention idea. It needs to be composed of chromium ion replacement material, electrostatic adsorption material, ammonia reduction material, magnetic material and coating material. The weight ratio of the five materials is 100:95~105:1000~1200:90~110:50~60.

[0024] Preparation method of chromium ion replacement material: 1) Preparation of nano-SiO2 microspheres: The classic sol-gel method is used. 25-30 mL of double-distilled water, 65-85 mL of anhydrous ethanol, and 15-20 mL of ammonia water are mixed and heated to a constant temperature in an oil bath at 35-40℃. 0.8 g of 99% tetraethyl orthosilicate is added dropwise under strong stirring. The reaction is continued with vigorous stirring for 30-40 min. In this step, tetraethyl orthosilicate undergoes hydrolysis under alkaline conditions to obtain silica spheres as seeds. Then, 6.2 g of tetraethyl orthosilicate is added dropwise, and the reaction is continued for 2-3 h. Finally, the nano-SiO2 microspheres are obtained by centrifugation and drying.

[0025] 2) Preparation of nano-SiO2-APTES: 10g of the nano-SiO2 spheres from step 1) were added to 80-100mL of anhydrous ethanol and dispersed by ultrasonication to obtain a suspension. 60-80mL of anhydrous ethanol and 25-35mL of deionized water were added to a two-necked flask. A trace amount of glacial acetic acid was added to adjust the pH to 5-6. 2-4mL of silane coupling agent KH-550 (Dongguan Kangjin New Material Technology Co., Ltd.) was added dropwise to the flask, and the mixture was stirred thoroughly for hydrolysis. The nano-SiO2 sphere suspension was then added dropwise to the flask. The ethoxy group (-OCH2CH3) in the silane coupling agent reacted with water to generate silanol groups (-Si-OH), which underwent dehydration condensation with the silanol groups on the nano-SiO2 spheres, thus achieving the grafting modification. The reaction was carried out at room temperature for 18-24 hours. h, then the reaction solution was centrifuged and washed with anhydrous ethanol, anhydrous THF and acetone respectively. The solid was dispersed with deionized water and freeze-dried to obtain a white solid product, which is the product nano SiO2-APTES.

[0026] 3) Preparation of α-bromocitric acid: Carboxylic acids react with halogens in the presence of a catalytic amount of reagent to convert carboxylic acids into acyl halides. The α-H of the acyl halide has high reactivity and is easily converted to the enol form. The α-hydrogen is replaced by a halogen to form an α-haloacyl halide, which then undergoes an exchange reaction with the carboxylic acid to obtain α-halocarboxylic acid, i.e., the Hel-Ulha-Zelinsky reaction. In a bromination reactor, 10g of citric acid, 80-100mL of anhydrous ethanol, and 0.1-0.4g of bromosuccinimide catalyst are added. The temperature is raised to 65-75℃, and then 18-22mL of bromine is added dropwise. After the addition is complete, the temperature is maintained at 65-75℃ for 3-4 hours. Excess bromine, hydrogen bromide, and ethanol are removed by vacuum distillation to obtain α-bromocitric acid.

[0027] 4) Preparation of α-bromomalonic acid: Add 10g of malonic acid, 80-100mL of anhydrous ethanol, and 0.1-0.3g of bromosuccinimide catalyst to another bromination reactor. Heat to 65-75℃, then add 17-19mL of bromine dropwise. After the addition is complete, keep the temperature at 65-75℃ for 3-4 hours. Remove excess bromine, hydrogen bromide, and ethanol by vacuum distillation to obtain α-bromomalonic acid.

[0028] 5) Preparation of chromium ion replacement material, namely SiO2-APTES-PC / CA: Add 60-80 mL of deionized water to a three-necked flask, then add 4 g of α-bromocitric acid from step 3) and 2-3 g of α-bromomalonic acid from step 4) to the three-necked flask, add 0.2-0.3 g of potassium carbonate, heat in an oil bath at 30-40℃ until constant temperature, and stir thoroughly for 10-20 min; then slowly add 20-30 g of nano-SiO2-APTES from step 2), reflux for 2-3 h under magnetic stirring, filter, wash with water, dry, and the amino groups grafted on the surface of nano-SiO2 undergo Hoffmann alkylation reaction with α-bromomalonic acid and α-bromocitric acid to obtain the chromium ion replacement material, namely SiO2-APTES-PC / CA.

[0029] The electrostatic adsorption material contains one of the following carriers: kaolinite, montmorillonite, diatomaceous earth, and magnesium silicate. This material is prepared through a series of processes.

[0030] 1) Carrier activation treatment: Weigh 40g of one of the following: kaolinite, montmorillonite, diatomaceous earth, or magnesium silicate. Add it to 400mL of 0.75~1.25mol / L sodium hydroxide solution and ultrasonically disperse for 20~30 min to increase the Al content on the carrier surface. 3+ Si 4+ Once the cations are exposed, the surface charge of the support is increased. The reaction is carried out at 60-80℃ for 5-6 hours. The mixture is then filtered, washed until neutral, and dried to obtain the activated support.

[0031] 2) Add 20g of the activated carrier from step 1) to a three-necked flask containing 80-100mL toluene, and sonicate for 15-20min. Under the protection of nitrogen (60-80 mL / min), slowly raise the temperature of the mixed solution to 105-110℃, and add 3-5g of 3-aminopropyltrimethylethylsilane (APTES). The ethoxy group (-OCH2CH3) in the silane coupling agent will react with water to form a silanol group (-Si-OH), which will undergo dehydration condensation with the silanol group on the activated carrier. Continue stirring for 12-15h, then filter, wash, and purify with anhydrous ethanol for 12-15h to remove unreacted ATPES. Then dry under vacuum at 70-80℃ for 12-15h to obtain the material used in the experiment, the activated carrier-APTES.

[0032] 3) Under nitrogen protection, 50-60 mL of dichloromethane and 0.025-0.035 mol of EDTA were transferred, and 2-3 mL of thionyl chloride was added dropwise under constant pressure. The EDTA reacted with thionyl chloride to prepare acyl chloride, and 1 g of the activated support-APTES from step 2) was quickly added. The acyl chloride reacted with 3-aminopropyltriethoxysilane on the surface of the activated support to form an amide compound. The reaction was carried out at room temperature for 2-3 h, filtered, and washed with 8 mL of dichloromethane, 8 mL of acetone, 10 mL of deionized water, 10 mL of 0.15-0.25 mol / L sodium bicarbonate solution, and 10 mL of deionized water. The product "activated support-APTES-EDTA" was obtained and dried at 50-60 °C, which is the electrostatic adsorption material.

[0033] Preparation method of ammonia-reducing material: (1) Add 6.5~7.5g KOH, 6.5g Al2(SO4)3·18H2O, and 3.5~4.0g 10nm granular graphene oxide (Guangzhou Emi Graphene Technology Co., Ltd.) sequentially to a beaker containing 600~650mL of deionized water under stirring, and stir for 30~40min to obtain solution A;

[0034] (2) Measure 500-550 mL of anhydrous ethanol into a beaker, and slowly add 183 g of tetraethyl orthosilicate under strong stirring. After the addition is complete, continue stirring for 30-40 min to obtain solution B.

[0035] (3) Under stirring, slowly add solution B to solution A, and continue stirring for 60-70 min after the addition is complete; transfer to a reaction vessel lined with polytetrafluoroethylene, and react in an oven at 165-175℃ for 40-50 h. After the reaction is complete, wash the product with deionized water until neutral, and dry in an oven at 90-100℃; place the dried product in a muffle furnace and calcine at 540-580℃ for 20-25 h to obtain zeolite; place the zeolite product in 500 mL of 0.8-1.4 mol / L NaCl solution and react in a water bath constant temperature shaking box at 30-45℃ for 8-12 h, rinse with deionized water, and dry to obtain ammonia-reducing material.

[0036] Preparation method of magnetic materials: (1) Add 20-30 mL of deionized water to 70-80 mL of ethylene glycol and stir, then add 32.0 g of isobutanolamine and 6.0-7.0 g of diethanolamine and stir for 5-10 min to obtain solution A;

[0037] (2) Dissolve 3.0g FeCl2·4H2O in 30~40mL of deionized water, then add 60~70mL of ethylene glycol while stirring to obtain solution B;

[0038] (3) Add 20-30 mL of deionized water to 70-80 mL of ethylene glycol, then add 5.0 g of FeCl3·6H2O, and stir for 5 min to obtain solution C;

[0039] (4) Divide solution A into two equal parts, mix one part with solution B and the other part with solution C; mix and stir the two mixed solutions for 20-30 minutes, then pour them into a polyimide liner, cover and seal with tape, place in an oven at 90-100℃, keep at a constant temperature for 5-10 hours, cool naturally to room temperature, separate the black product with a magnet, wash with 100-150 mL of deionized water, then wash with 100-150 mL of anhydrous ethanol 2-4 times, and dry in an oven at 30-40℃ for 6-12 hours to obtain the magnetic material iron(III) oxide.

[0040] The coating material is one of hydroxymethyl cellulose, carboxymethyl cellulose, polyacrylamide, polyethyleneimine, and polyacrylamide. It utilizes the large number of hydroxyl groups in its molecules to coat chromium ion replacement materials, electrostatic adsorption materials, ammonia-reducing materials, and magnetic materials together through hydrogen bonds and van der Waals forces to obtain a chromium removal and ammonia-reducing agent. The weight ratio of the five materials is 100:95~105:1000~1200:90~110:10~15. Specific coating process: 100g of chromium ion replacement material, 95-105g of electrostatic adsorption material, 1000-1200g of ammonia-reducing material, and 95-105g of magnetic material are poured into a three-necked flask and stirred at room temperature for 30-40 minutes. While stirring, an aqueous solution containing 50-60g of coating material dissolved in 2000-2400mL is sprayed into the three-necked flask. The product obtained from the above operation is then placed in a blower dryer for drying. First, it is dried at 70-80℃ for 1 hour, and then the temperature is raised to 110-115℃ for 1-1.5 hours. After drying, the chromium removal and ammonia-reducing agent is obtained.

[0041] In this invention, the combined use of chromium ion replacement material and electrostatic adsorption material in the chromium removal and ammonia reduction agent is the key to achieving deep chromium removal from chromium-containing collagen.

[0042] In this invention, the use of ammonia-reducing materials is a key material for reducing ammonia content and improving the freshness of protein powder.

[0043] In this invention, one of the key factors in achieving rapid solid-liquid separation is the use of magnetic materials, and another key factor is the coating of the other four materials together with a coating material.

[0044] This invention relates to the application of a chromium-removing and ammonia-reducing agent in a chromium-containing collagen solution. The collagen solution contains 20.6 mg / L of chromium, 203 g / L of collagen, pH 9, and 200 mg / L of ammonia. The specific steps for chromium removal and ammonia reduction are as follows: 1 L of the above solution is measured, and its pH is adjusted to 10.5-11.5 with alkali, as this pH range is more conducive to chromium removal. Then, 12-18 g of the chromium-removing and ammonia-reducing agent is added, and the mixture is stirred at 60-90℃ for 2-3 hours. Sulfuric acid is then added to adjust the pH to 6-7, converting ammonia into ammonium ions. The ammonium ions then undergo ion exchange with the ammonia-reducing material to remove ammonium. Stirring continues for 2.5-3.5 hours, after which the process is stopped and allowed to stand. A magnet is placed under the three-necked flask to achieve rapid solid-liquid separation using magnetic and natural sedimentation effects. The collagen solution and chromium slag are obtained by decantation.

[0045] The present invention describes adjusting and maintaining the pH of the collagen solution to 10.5~11.5. The alkali used in the pH adjustment process is one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, calcium oxide, magnesium oxide, and calcium hydroxide. The enhanced auxiliary means refer to a reaction temperature of 60~90℃ and a strong stirring speed of 100~300r / min.

[0046] Unless otherwise specified in this invention, all raw materials are commercially available products well known to those skilled in the art.

[0047] Compared with existing technologies, the present invention has the following advantages and effects:

[0048] The collagen solution obtained after alkaline hydrolysis of chromium-containing leather scraps contains three types of chromium-containing substances: a small amount of chromium remains chelated with carboxyl, hydroxyl, and amino groups in the collagen; a small amount of Cr(OH)3 colloid; and some chromium reacts with hydroxyl groups to form polyhydroxy chromium complex ions, which traditional chromium removal agents cannot remove. The collagen solution obtained by the alkaline method contains a certain amount of ammonia, and the ammonia content directly affects the freshness of the product and the quality of the protein powder. There are currently no reports on how to reduce the ammonia content in collagen. This invention provides a chromium removal and ammonia reduction agent for chromium-containing collagen solutions, which has the following characteristics:

[0049] Firstly, by utilizing the strong coordination ability of citrate ions with chromium ions, and the small molecular weight and high permeability of malonic acid, the two work together to replace chromium ions in collagen.

[0050] Secondly, a chromium ion replacement material, SiO2-APTES-PC / CA, was prepared by grafting nano-SiO2 spheres with citric acid and malonic acid. This material enables the removal of chromium ions through precipitation.

[0051] Third, the electrostatic adsorption material carrier is activated by alkali, which makes its surface carry more positive charges, which is conducive to adsorption with Cr(OH)3 colloid and polyhydroxy chromium complex ions.

[0052] Fourth, the surface of the electrostatic adsorption material is grafted with EDTA, which on the one hand utilizes the strong coordination between EDTA and chromium ions to remove chromium, and on the other hand facilitates its adsorption of chromium-containing collagen.

[0053] Fifth, the ammonia-reducing material reduces ammonium ions through ion exchange, thereby improving product freshness.

[0054] Sixth, add magnetic materials to achieve rapid solid-liquid separation using magnets.

[0055] Seventh, adding coating materials to coat chromium ion replacement materials, electrostatic adsorption materials, ammonia-reducing materials, and magnetic materials together increases the size of solid particles, which is conducive to the rapid sedimentation of chromium removal and ammonia-reducing agents and achieves efficient solid-liquid separation. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the structure of the chromium removal and ammonia reduction agent material prepared according to the present invention. Detailed Implementation

[0057] The invention will be further illustrated below with examples.

[0058] Example 1

[0059] Preparation method of chromium ion replacement materials:

[0060] 1) Preparation of nano-SiO2 spheres: 27 mL of deionized water, 75 mL of anhydrous ethanol, and 18 mL of ammonia were mixed and heated to a constant temperature in an oil bath at 35 °C. 0.8 g of 99% tetraethyl orthosilicate was added dropwise under vigorous stirring. The reaction was continued with vigorous stirring for 35 min to obtain a silica sphere seed solution. Then, 6.2 g of tetraethyl orthosilicate was added dropwise, and the reaction was continued for 2.5 h. Finally, the mixture was centrifuged and dried to obtain nano-SiO2 spheres.

[0061] 2) Preparation of nano-SiO2-APTES: 10g of nano-SiO2 spheres from step 1) were dispersed in 90mL of anhydrous ethanol and ultrasonically dispersed evenly to obtain a nano-SiO2 sphere suspension. 70mL of anhydrous ethanol and 30mL of deionized water were added to a two-necked flask. A trace amount of glacial acetic acid was added to adjust the pH to 5-6. 3mL of silane coupling agent KH-550 was added dropwise to the flask and stirred thoroughly for hydrolysis. The nano-SiO2 sphere suspension was then added dropwise to the flask and reacted at room temperature for 21 h. After centrifugation, the reaction solution was washed and centrifuged with 25mL of anhydrous ethanol, 15mL of anhydrous tetrahydrofuran, and 15mL of acetone, respectively. The solid was dispersed in 30mL of deionized water and freeze-dried to obtain a white solid product, which is nano-SiO2-APTES.

[0062] 3) Preparation of α-bromocitric acid: 10g of citric acid, 90mL of anhydrous ethanol, and 0.25g of bromosuccinimide catalyst were added to a bromination reactor. The temperature was raised to 70℃, and then 20mL of bromine was added dropwise. After the addition was completed, the temperature was maintained at 70℃ for 3.5h. Excess bromine, hydrogen bromide, and ethanol were removed by vacuum distillation to obtain α-bromocitric acid.

[0063] 4) Preparation of α-bromomalonic acid: In another bromination reactor, add 10 mL of malonic acid, 90 mL of anhydrous ethanol, and 0.2 g of bromosuccinimide catalyst. Heat to 70 °C, then add 18 mL of bromine dropwise. After the addition is complete, keep at 70 °C for 3.5 h. Remove excess bromine, hydrogen bromide, and ethanol by vacuum distillation to obtain α-bromomalonic acid.

[0064] 5) Preparation of chromium ion replacement material, i.e., SiO2-APTS-PC / CA: Add 70mL of deionized water to a three-necked flask, then add 4g of α-bromocitric acid from step 3) and 2.5g of α-bromomalonic acid from step 4) to the three-necked flask, add 0.25g of potassium carbonate, heat in an oil bath at 30~40℃ until constant temperature, and stir thoroughly for 15min; then slowly add 25g of nano-SiO2-APTES from step 2), reflux for 2.5h under magnetic stirring, filter, wash with water, dry, and the amino groups grafted on the surface of nano-SiO2 undergo Hoffmann alkylation reaction with α-bromomalonic acid and α-bromocitric acid to obtain the chromium ion replacement material, i.e., SiO2-APTES-PC / CA.

[0065] Electrostatic adsorption materials contain diatomaceous earth as a carrier, which is obtained by modifying these diatomaceous earth carriers.

[0066] 1) Activation treatment of the carrier: Weigh 40g of diatomaceous earth, add 400mL of 1mol / L hydrochloric acid solution, ultrasonically disperse for 25min, react at 70℃ for 5.5h, filter, wash until neutral, dry, and obtain the activated carrier;

[0067] 2) Add 20g of the activated carrier from step 1) to a three-necked flask containing 90mL of toluene, sonicate for 15min, and slowly raise the temperature of the mixed solution to 105℃ under nitrogen flow rate of 70 mL / min. Add 4g of 3-aminopropyltriethoxysilane and continue stirring for 13.5h. Then filter, wash, purify with anhydrous ethanol for 13.5h, and vacuum dry at 75℃ for 13.4h to obtain the activated carrier-APTES.

[0068] 3) Under nitrogen protection, 55 mL of dichloromethane and 0.030 mol of EDTA were transferred, and 2.5 mL of thionyl chloride was added dropwise under constant pressure. Then, 1 g of the activated support - APTES from step 2) was quickly added. The mixture was reacted at room temperature for 2.5 h, filtered, washed with 8 mL of dichloromethane, 8 mL of acetone, 10 mL of deionized water, 10 mL of 0.2 mol / L sodium bicarbonate aqueous solution, and 10 mL of deionized water, and dried at 55 °C to obtain the electrostatic adsorption material.

[0069] Preparation method of ammonia-reducing material: (1) Add 7 g KOH, 6.5 g Al2(SO4)3·18H2O and 4.0 g 10 nm granular graphene oxide to a beaker containing 650 mL of deionized water in sequence under stirring, and stir for 35 min to obtain solution A;

[0070] (2) Measure 500 mL of anhydrous ethanol into a beaker, and slowly add 183 g of tetraethyl orthosilicate under strong stirring. After the addition is complete, continue stirring for 30 min to obtain solution B.

[0071] (3) Under stirring, solution B is slowly added to solution A, and stirring is continued for 65 min after the addition is complete; the product is transferred to a reaction vessel lined with polytetrafluoroethylene and reacted in an oven at 170℃ for 45 h. After the reaction is completed, the product is washed with deionized water until neutral and dried in an oven at 95℃; the dried product is placed in a muffle furnace and calcined at 560℃ for 22.5 h to obtain zeolite; the zeolite product is placed in 500 mL of 1 mol / L NaCl solution and reacted in a water bath constant temperature shaking box at 38℃ for 10 h. The product is then rinsed with deionized water, dried, and the ammonia-reducing material is obtained.

[0072] Preparation method of magnetic materials: (1) Add 25 mL of deionized water to 75 mL of ethylene glycol and stir, then add 32.0 g of isobutanolamine and 6.5 g of diethanolamine, stir for 8 min to obtain solution A;

[0073] (2) Dissolve 3.0g FeCl2.4H2O in 35mL of deionized water, then add 65mL of ethylene glycol while stirring to obtain solution B;

[0074] (3) Add 25 mL of deionized water to 75 mL of ethylene glycol, then add 5.0 g of FeCl3·6H2O, and stir for 5 min to obtain solution C;

[0075] (4) Divide solution A into two equal parts, mix one part with solution B and the other part with solution C; mix and stir the two mixed solutions for 25 min, then pour them into a polyimide liner, cover and seal with tape, place in an oven at 95°C for 7.5 h, cool naturally to room temperature, separate the black product with a magnet, wash with 125 mL of deionized water, then wash three times with 125 mL of anhydrous ethanol, and dry in an oven at 30°C for 9 h to obtain the magnetic material iron(III) oxide.

[0076] 100g of chromium ion replacement material, 100g of electrostatic adsorption material, 1100g of ammonia-reducing material, and 100g of magnetic material were poured into a three-necked flask and stirred at room temperature for 35 minutes. Then, while stirring, 55g of polyacrylamide dissolved in 2200mL of water was sprayed into the three-necked flask. The product obtained from the above operation was then placed in a blower dryer and dried. First, it was dried at 75℃ for 1 hour, and then the temperature was raised to 110℃ for 1 hour. After drying, the chromium removal and ammonia-reducing agent was obtained.

[0077] Take 6.5 kg of chromium-containing waste blue leather scraps (Cr2O3 3.5%, collagen 80%, ash 5.5%) from Fujian Xingye Leather Technology Co., Ltd., add 15 L of water and 650 g of calcium oxide, stir and react at 100 °C for 4 h, filter to obtain 4.5 kg of filter residue and 14 L of filtrate. The filtrate contains 20.6 mg / L of chromium, 203 g / L of collagen, pH 9.0, and 200 mg / L of ammonia. This process removes 99.8% of the chromium. Take 1L of the above filtrate and adjust the pH to 10.5 with potassium hydroxide (maintain the system pH at 10.5 during the treatment). Then add 16.0g of the chromium removal and ammonia reduction agent prepared above to the solution and stir at 60℃ for 2 hours. Add sulfuric acid to adjust the pH of the solution to 6 and continue stirring for 2.5 hours. Then stop the treatment and let it stand. Add a magnet to the bottom of the three-necked flask and use magnetic force and natural sedimentation to quickly separate the solid and liquid. Obtain the collagen solution and chromium slag by decantation and finally separate the solid and liquid.

[0078] Example 2

[0079] Preparation method of chromium ion replacement materials:

[0080] 1) Preparation of nano-SiO2 spheres: 25 mL of deionized water, 65 mL of anhydrous ethanol, and 15 mL of ammonia were mixed and heated to a constant temperature in an oil bath at 35 °C. 0.8 g of 99% tetraethyl orthosilicate was added dropwise under vigorous stirring. The reaction was continued with vigorous stirring for 30 min to obtain a silica sphere seed solution. Then, 6.2 g of tetraethyl orthosilicate was added dropwise, and the reaction was continued for 2 h. Finally, the solution was centrifuged and dried to obtain nano-SiO2 spheres.

[0081] 2) Preparation of nano-SiO2-APTES: 10g of nano-SiO2 spheres from step 1) were dispersed in 80mL of anhydrous ethanol and ultrasonically dispersed evenly to obtain a nano-SiO2 sphere suspension. 60mL of anhydrous ethanol and 25mL of deionized water were added to a two-necked flask. A trace amount of glacial acetic acid was added to adjust the pH to 5-6. 2mL of silane coupling agent KH-550 was added dropwise to the flask and stirred thoroughly for hydrolysis. The nano-SiO2 sphere suspension was then added dropwise to the flask and reacted at room temperature for 18h. After centrifugation, the reaction solution was washed and centrifuged with 25mL of anhydrous ethanol, 15mL of anhydrous tetrahydrofuran, and 15mL of acetone, respectively. The solid was dispersed in 30mL of deionized water and freeze-dried to obtain a white solid product, which is nano-SiO2-APTES.

[0082] 3) Preparation of α-bromocitric acid: Add 10g of citric acid, 80mL of anhydrous ethanol, and 0.1g of bromosuccinimide catalyst to a bromination reactor, heat to 65℃, and then add 18mL of bromine dropwise. After the addition is complete, keep the temperature at 65℃ for 3h, and remove excess bromine, hydrogen bromide, and ethanol by vacuum distillation to obtain α-bromocitric acid.

[0083] 4) Preparation of α-bromomalonic acid: 10 mL of malonic acid and 80 mL of anhydrous ethanol were added to another bromination reactor. 0.1 g of bromosuccinimide catalyst was added, the temperature was raised to 65 °C, and then 17 mL of bromine was added dropwise. After the addition was completed, the temperature was maintained at 65 °C for 3 h. Excess bromine, hydrogen bromide and ethanol were removed by vacuum distillation to obtain α-bromomalonic acid.

[0084] 5) Preparation of chromium ion replacement material, i.e., SiO2-APTS-PC / CA: Add 60mL of deionized water to a three-necked flask, then add 4g of α-bromocitric acid from step 3) and 2g of α-bromomalonic acid from step 4) to the three-necked flask, add 0.2g of potassium carbonate, heat in an oil bath at 30℃ until constant temperature and stir thoroughly for 10min; then slowly add 20g of nano-SiO2-APTES from step 2), reflux for 2h under magnetic stirring, filter, wash with water, dry, and the amino groups grafted on the surface of nano-SiO2 undergo Hoffmann alkylation reaction with α-bromomalonic acid and α-bromocitric acid to obtain the chromium ion replacement material, i.e., SiO2-APTES-PC / CA.

[0085] The electrostatic adsorption material contains kaolinite as a carrier, and is obtained by modifying these kaolinite carriers.

[0086] 1) Activation treatment of the carrier: Weigh 40g of kaolinite, add 400mL of 0.75mol / L hydrochloric acid solution and sonicate for 20min, react at 60℃ for 5h, filter, wash until neutral, dry to obtain the activated carrier;

[0087] 2) Add 20g of the activated carrier from step 1) to a three-necked flask containing 80mL of toluene, sonicate for 15min, and slowly raise the temperature of the mixed solution to 105℃ under the protection of nitrogen flow rate of 60 mL / min. Add 3g of 3-aminopropyltriethoxysilane and continue stirring for 12h. Then filter, wash, purify with anhydrous ethanol for 12h, and vacuum dry at 70℃ for 12h to obtain the activated carrier-APTES.

[0088] 3) Under nitrogen protection, 50 mL of dichloromethane and 0.025 mol of EDTA were transferred, and 2 mL of thionyl chloride was added dropwise under constant pressure. Then, 1 g of the activated support - APTES from step 2) was quickly added. The mixture was reacted at room temperature for 2 h, filtered, washed with 8 mL of dichloromethane, 8 mL of acetone, 10 mL of deionized water, 10 mL of 0.15 mol / L sodium bicarbonate aqueous solution, and 10 mL of deionized water, and dried at 50 °C to obtain the electrostatic adsorption material.

[0089] Preparation method of ammonia-reducing material: (1) Add 6.5g KOH, 6.5g Al2(SO4)3·18H2O and 3.5g 10nm granular graphene oxide to a beaker containing 600mL of deionized water in sequence under stirring, and stir for 30min to obtain solution A.

[0090] (2) Measure 500 mL of anhydrous ethanol into a beaker, and slowly add 183 g of tetraethyl orthosilicate under strong stirring. After the addition is complete, continue stirring for 30 min to obtain solution B.

[0091] (3) Under stirring, solution B is slowly added to solution A, and stirring is continued for 60 min after the addition is complete; the product is transferred to a reaction vessel lined with polytetrafluoroethylene and reacted in an oven at 165℃ for 40 h. After the reaction is completed, the product is washed with deionized water until neutral and dried in an oven at 90℃; the dried product is placed in a muffle furnace and calcined at 540℃ for 20 h to obtain zeolite; the zeolite product is placed in 500 mL of 0.8 mol / L NaCl solution and reacted in a water bath constant temperature shaking box at 30℃ for 8 h. The product is then rinsed with deionized water, dried, and the ammonia-reducing material is obtained.

[0092] Preparation method of magnetic materials: (1) Add 20 mL of deionized water to 70 mL of ethylene glycol and stir, then add 32.0 g of isobutanolamine and 6.0 g of diethanolamine and stir for 5 min to obtain solution A;

[0093] (2) Dissolve 3.0g FeCl2.4H2O in 30mL of deionized water, then add 60mL of ethylene glycol while stirring to obtain solution B;

[0094] (3) Add 20 mL of deionized water to 70 mL of ethylene glycol, then add 5.0 g of FeCl3·6H2O, and stir for 5 min to obtain solution C;

[0095] (4) Divide solution A into two equal parts, mix one part with solution B and the other part with solution C; mix and stir the two mixed solutions for 20 minutes, then pour them into a polyimide liner, cover and seal with tape, put in an oven at 90°C for 5 hours, cool naturally to room temperature, separate the black product with a magnet, wash with 100 mL of deionized water, then wash twice with 100 mL of anhydrous ethanol, and dry in an oven at 30°C for 6 hours to obtain the magnetic material iron(III) oxide.

[0096] 100g of chromium ion replacement material, 95g of electrostatic adsorption material, 1000g of ammonia-reducing material, and 95g of magnetic material were poured into a three-necked flask and stirred at room temperature for 30 minutes. While stirring, 50g of hydroxymethyl cellulose dissolved in 2000mL of water was sprayed into the three-necked flask. The product obtained from the above operation was then placed in a blower dryer and dried at 70℃ for 1 hour, and then the temperature was raised to 110℃ for 1~1.5 hours. After drying, the chromium removal and ammonia-reducing agent was obtained.

[0097] Take 6.5 kg of chromium-containing waste blue leather scraps (Cr2O3 3.5%, collagen 80%, ash 5.5%) from Fujian Xingye Leather Technology Co., Ltd., add 15 L of water and 650 g of calcium oxide, stir and react at 100 °C for 4 h, filter to obtain 4.5 kg of filter residue and 14 L of filtrate. The filtrate contains 20.6 mg / L of chromium, 203 g / L of collagen, pH 9.0, and 200 mg / L of ammonia. This process removes 99.8% of the chromium. Take 1L of the above filtrate and adjust the pH to 10.5 with calcium hydroxide (maintain the system pH at 10.5 during the treatment). Then add 12.0g of the chromium removal and ammonia reduction agent prepared above to the solution, and stir at 60℃ for 2 hours. Add sulfuric acid to adjust the pH of the solution to 6, and continue stirring for 2.5 hours. Then stop the treatment and let it stand. Add a magnet to the bottom of the three-necked flask and use magnetic effect and natural sedimentation to quickly separate the solid and liquid. Obtain the collagen solution and chromium slag by decantation. Finally, separate the solid and liquid.

[0098] Example 3

[0099] Preparation method of chromium ion replacement materials:

[0100] 1) Preparation of nano-SiO2 spheres: 30 mL of deionized water, 85 mL of anhydrous ethanol, and 20 mL of ammonia were mixed and heated to a constant temperature in an oil bath at 40 °C. 0.8 g of 99% tetraethyl orthosilicate was added dropwise under vigorous stirring. The reaction was continued with vigorous stirring for 40 min to obtain a silica sphere seed solution. Then, 6.2 g of tetraethyl orthosilicate was added dropwise, and the reaction was continued for 3 h. Finally, the solution was centrifuged and dried to obtain nano-SiO2 spheres.

[0101] 2) Preparation of nano-SiO2-APTES: 10g of nano-SiO2 spheres from step 1) were dispersed in 100mL of anhydrous ethanol and ultrasonically dispersed evenly to obtain a nano-SiO2 sphere suspension. 80mL of anhydrous ethanol and 35mL of deionized water were added to a two-necked flask. A trace amount of glacial acetic acid was added to adjust the pH to 5-6. 4mL of silane coupling agent KH-550 was added dropwise to the flask and stirred thoroughly for hydrolysis. The nano-SiO2 sphere suspension was then added dropwise to the flask and reacted at room temperature for 24h. After centrifugation, the reaction solution was washed and centrifuged with 25mL of anhydrous ethanol, 15mL of anhydrous tetrahydrofuran, and 15mL of acetone, respectively. The solid was dispersed in 30mL of deionized water and freeze-dried to obtain a white solid product, which is nano-SiO2-APTES.

[0102] 3) Preparation of α-bromocitric acid: Add 10g of citric acid, 100mL of anhydrous ethanol, and 0.4g of bromosuccinimide catalyst to a bromination reactor, heat to 75℃, and then add 22mL of bromine dropwise. After the addition is complete, keep the temperature at 75℃ for 4h, and remove excess bromine, hydrogen bromide, and ethanol by vacuum distillation to obtain α-bromocitric acid.

[0103] 4) Preparation of α-bromomalonic acid: Add 10 mL of malonic acid and 100 mL of anhydrous ethanol to another bromination reactor, add 0.3 g of bromosuccinimide catalyst, heat to 75 °C, and then add 19 mL of bromine dropwise. After the addition is complete, keep warm at 75 °C for 4 h, and remove excess bromine, hydrogen bromide and ethanol by vacuum distillation to obtain α-bromomalonic acid.

[0104] 5) Preparation of chromium ion replacement material, i.e., SiO2-APTS-PC / CA: Add 80mL of deionized water to a three-necked flask, then add 4g of α-bromocitric acid from step 3) and 3g of α-bromomalonic acid from step 4) to the three-necked flask, add 0.3g of potassium carbonate, heat in an oil bath at 40℃ until constant temperature, and stir thoroughly for 20min; then slowly add 30g of nano-SiO2-APTES from step 2), reflux for 3h under magnetic stirring, filter, wash with water, dry, and the amino groups grafted on the surface of nano-SiO2 undergo Hoffmann alkylation reaction with α-bromomalonic acid and α-bromocitric acid to obtain the chromium ion replacement material, i.e., SiO2-APTES-PC / CA.

[0105] The electrostatic adsorption material contains montmorillonite as a carrier, and is obtained by modifying montmorillonite.

[0106] 1) Activation treatment of the carrier: Weigh 40g of montmorillonite, add 400mL of 1.25mol / L hydrochloric acid solution and ultrasonically disperse for 30min, react at 80℃ for 6h, filter, wash until neutral, dry, and obtain the activated carrier;

[0107] 2) Add 20g of the activated carrier from step 1) to a three-necked flask containing 100mL of toluene, sonicate for 20min, and slowly raise the temperature of the mixed solution to 110℃ under nitrogen flow rate of 80 mL / min. Add 5g of 3-aminopropyltriethoxysilane and continue stirring for 15h. Then filter, wash, purify with anhydrous ethanol for 15h, and vacuum dry at 80℃ for 15h to obtain the activated carrier-APTES.

[0108] 3) Under nitrogen protection, 60 mL of dichloromethane and 0.035 mol of EDTA were transferred, and 3 mL of thionyl chloride was added dropwise under constant pressure. Then, 1 g of the activated support - APTES from step 2) was quickly added. The mixture was reacted at room temperature for 3 h, filtered, washed with 8 mL of dichloromethane, 8 mL of acetone, 10 mL of deionized water, 10 mL of 0.25 mol / L sodium bicarbonate aqueous solution, and 10 mL of deionized water, and dried at 60 °C to obtain the electrostatic adsorption material.

[0109] Preparation method of ammonia-reducing material: (1) Add 7.5g KOH, 6.5g Al2(SO4)3·18H2O, and 4.0g 10nm granular graphene oxide to a beaker containing 650mL of deionized water in sequence under stirring, and stir for 40min to obtain solution A.

[0110] (2) Measure 550 mL of anhydrous ethanol into a beaker, and slowly add 183 g of tetraethyl orthosilicate under strong stirring. After the addition is complete, continue stirring for 40 min to obtain solution B.

[0111] (3) Under stirring, solution B is slowly added to solution A, and stirring is continued for 70 min after the addition is complete; the product is transferred to a reaction vessel lined with polytetrafluoroethylene and reacted in an oven at 175℃ for 50 h. After the reaction is completed, the product is washed with deionized water until neutral and dried in an oven at 100℃; the dried product is placed in a muffle furnace and calcined at 580℃ for 25 h to obtain zeolite; the zeolite product is placed in 500 mL of 1.4 mol / L NaCl solution and reacted in a water bath constant temperature shaking box at 45℃ for 12 h. The product is then rinsed with deionized water, dried, and the ammonia-reducing material is obtained.

[0112] Preparation method of magnetic materials: (1) Add 30 mL of deionized water to 80 mL of ethylene glycol and stir, then add 32.0 g of isobutanolamine and 7.0 g of diethanolamine, stir for 10 min to obtain solution A;

[0113] (2) Dissolve 3.0g FeCl2.4H2O in 40mL of deionized water, then add 70mL of ethylene glycol while stirring to obtain solution B;

[0114] (3) Add 30 mL of deionized water to 80 mL of ethylene glycol, then add 5.0 g of FeCl3·6H2O, and stir for 5 min to obtain solution C;

[0115] (4) Divide solution A into two equal parts, mix one part with solution B and the other part with solution C; mix and stir the two mixed solutions for 30 min, then pour them into a polyimide liner, cover and seal with tape, put in an oven at 100℃, keep the temperature constant for 10 h, cool naturally to room temperature, separate the black product with a magnet, wash with 150 mL of deionized water, then wash 4 times with 150 mL of anhydrous ethanol, and dry in an oven at 40℃ for 12 h to obtain the magnetic material iron(III) oxide.

[0116] 100g of chromium ion replacement material, 105g of electrostatic adsorption material, 1200g of ammonia-reducing material, and 105g of magnetic material were poured into a three-necked flask and stirred at room temperature for 40 minutes. Then, while stirring, 60g of carboxymethyl cellulose dissolved in 2400mL of water was sprayed into the three-necked flask. The product obtained from the above operation was then placed in a blower dryer and dried at 80℃ for 1 hour, and then the temperature was raised to 115℃ for 1.5 hours. After drying, the chromium removal and ammonia-reducing agent was obtained.

[0117] Take 6.5 kg of chromium-containing waste blue leather scraps (Cr2O3 3.5%, collagen 80%, ash 5.5%) from Fujian Xingye Leather Technology Co., Ltd., add 15 L of water and 650 g of calcium oxide, stir and react at 100 °C for 4 h, filter to obtain 4.5 kg of filter residue and 14 L of filtrate. The filtrate contains 20.6 mg / L of chromium, 203 g / L of collagen, pH 9.0, and 200 mg / L of ammonia. This process removes 99.8% of the chromium. Take 1L of the above filtrate and adjust the pH to 11.5 with calcium hydroxide (maintain the system pH at 11.5 during the treatment). Then add 18.0g of the chromium removal and ammonia reduction agent prepared above to the solution, and stir at 80℃ for 3 hours. Add sulfuric acid to adjust the pH of the solution to 7, and continue stirring for 3.5 hours. Then stop the treatment and let it stand. Add a magnet to the bottom of the three-necked flask and use magnetic force and natural sedimentation to quickly separate the solid and liquid. Obtain the collagen solution and chromium slag by decantation.

[0118] Table 1. Chromium and ammonia content and separation time after using three chromium removal and ammonia reduction agents.

[0119] Serial Number Implementation Examples Chromium concentration in collagen after use (ppm) Ammonia concentration in collagen after use (ppm) Solid-liquid separation time / s 1 Example 1 3.8 55.6 16.2 2 Example 2 3.2 23.1 14.1 3 Example 3 3.6 25.4 14.6

[0120] The experimental results are shown in Table 1. Example 2 showed the best chromium removal effect. The ammonia reduction and solid-liquid separation time were similar to those of Example 2 and Example 3. Therefore, Example 2 had the best overall effect. The following comparative experiments were all conducted with the product of Example 2.

[0121] 1) Comparison with market products: The chromium removal agents produced by Guangzhou Miaotong Water Treatment Technology Co., Ltd., models TMT-30A and RY-15, are compared with those in Example 2 under the same usage. The results are shown in Table 2.

[0122] Table 2 Comparison of Chromium and Ammonia Content and Separation Time after Use of Three Products

[0123] Serial Number Product Types Chromium concentration in collagen after chromium removal / ppm Ammonia concentration in collagen after use (ppm) Solid-liquid separation time / s 1 Example 2 3.2 23,5 14.3 2 Guangzhou Miaotong Water Treatment Technology Co., Ltd. Chromium Removal Agent Model MT-161 7.5 201.2 160.7 3 Guangzhou Miaotong Water Treatment Technology Co., Ltd. Chromium Removal Agent Model RY-15 10.8 200.3 175.6

[0124] 2) Other comparative experiments

[0125] Table 3 Chromium content and separation time after treatment with different materials

[0126] Serial Number Types of chromium removal and ammonia reduction agents Chromium concentration in collagen after addition / ppm Ammonia concentration in collagen after addition / ppm Solid-liquid separation time / s 1 No citric acid added 6.5 23.3 16.2 2 No malonic acid added 6.0 23.8 15.8 3 No malonic acid or citric acid added 8.0 23.5 15.5 4 Unchromium ion-displacement materials 8.8 24.2 16.7 5 Ungrafted EDTA 7.0 25.4 14.9 6 Electrostatic adsorption material not activated 7.5 24.5 15.3 7 Electrostatic adsorption material is not activated and is not grafted with EDTA. 9.1 25.5 14.8 8 No electrostatic adsorption material added 13.7 24.2 17.5 9 No wrapping material 4.1 23.8 112.3 10 Chromium-free ion-displacement materials, electrostatic adsorption materials 20.3 24.4 20.2 11 Unchromium ion-displacement materials and coating materials 9.2 25.2 59.7 12 No electrostatic adsorption materials or coating materials added 13.9 24.8 110.3 13 No ammonia-reducing materials added 3.2 201.1 14.5 14 Ammonia-reducing materials were not activated 3.2 122.2 15.7 15 No magnetic material added 3.2 23.4 40.5

[0127] As shown in Table 3, firstly, the addition of citric acid or malonic acid significantly increases the chromium removal effect, and the effect is even more significant when both are added simultaneously, as they have a synergistic effect; secondly, the electrostatic adsorption material significantly improves the chromium removal effect through activation treatment and grafting with EATD; thirdly, the use of coating materials greatly reduces the solid-liquid separation time; fourthly, ammonia-reducing materials can significantly reduce the ammonia content in collagen; fifthly, the activation treatment of ammonia-reducing materials is significantly more effective than the untreated materials; and sixthly, magnetic materials greatly shorten the solid-liquid separation time.

[0128] Product Performance Comparison

[0129] 1. Take 6.5 kg of chromium-containing waste blue leather scraps (Cr2O3 3.5%, collagen 80%, ash 5.5%) from Fujian Xingye Leather Technology Co., Ltd., add 15 L of water and 650 g of calcium oxide, stir and react at 100℃ for 4 h, filter to obtain 4.5 kg of filter residue and 14 L of filtrate. The filtrate has a chromium content of 20.6 mg / L, a collagen content of 230 g / L, a pH of 9.0, and an ammonia content of 200 mg / L. Take 5 L of this filtrate, add sulfuric acid to adjust the pH of the solution to 6.5, stir for 3.0 h, then stop the process and let it stand. Then separate the solid and liquid, concentrate the solution, and spray dry it using a micro spray dryer to obtain 1 kg of protein powder. This protein powder is "unremoved chromium and ammonia-reduced protein powder".

[0130] 2) Take 6.5 kg of chromium-containing waste blue leather scraps (Cr2O3 3.5%, collagen 80%, ash 5.5%) from Fujian Xingye Leather Technology Co., Ltd., add 15 L of water and 650 g of calcium oxide, stir at 100℃ for 4 h, filter to obtain 4.5 kg of filter residue and 14 L of filtrate. The filtrate has a chromium content of 20.6 mg / L, a collagen content of 230 g / L, a pH of 9.0, and an ammonia content of 200 mg / L. Take 5 L of this filtrate, adjust the pH to 11.0 with calcium hydroxide (maintain the system pH at 11.0 during the treatment), then add 15.0 g of chromium removal and ammonia reduction agent to the solution, and stir at 70℃ for 2.5 h; then add sulfuric acid to adjust the pH to 6.5, continue stirring for 3.0 h, then stop the treatment and let it stand. Using a magnet and natural sedimentation, the solid and liquid are quickly separated. Obtain the collagen solution and chromium residue by decantation. The solution was concentrated and then sprayed through a micro spray dryer to obtain 1 kg of protein powder, which is "chromium-removing and ammonia-reducing protein powder".

[0131] The chromium content, ash content, solubility, and bulk density of four types of protein powder—"unremoved chromium protein powder," "chromium-removed protein powder," "product of Fuxin Dacheng Biotechnology Co., Ltd.," and "product of Shandong Huasheng Chemical Technology Co., Ltd."—were tested. The results are shown in Table 4.

[0132] Table 4 Quality Index of Four Types of Protein Powder

[0133] product Chromium content / ppm Ash content / % Instant solubility / s Ammonia content / ppm Bulk density (looseness) Unremoved chromium-lowering protein powder 92.7 7.8 230 201.2 0.54 Chromium-removing and ammonia-reducing protein powder 8.1 6.0 150 23.2 0.44 #1 Protein Powder (Fuxin Dacheng Biotechnology Co., Ltd.) 55.0 8.7 240 400.7 0.50 #2 Protein Powder (Shandong Huasheng Chemical Technology Co., Ltd.) 86.5 8.5 210 450.9 0.58

[0134] Table 4 shows that the most significant change in protein powder treated with the chromium removal and ammonia reduction agent is the substantial reduction in chromium content compared to commercially available protein powders. Literature reports and actual alkaline production yield a chromium removal rate of around 95%, while this agent achieves a total chromium removal rate of 99.75%, with the product's chromium content far below national standards. The agent also significantly reduces ammonia content, improving the freshness and quality of the protein powder. Furthermore, it enhances other aspects of the protein powder's quality: ash content decreases, bulkiness increases, and water solubility is greatly improved. This is because the reduced chromium content decreases the chelation between protein molecules, improving bulkiness and solubility; the electrostatic adsorption material coordinates with some calcium ions in the solution, reducing the ash content of the protein powder.

[0135] Protein content determination method: Kjeldahl method.

[0136] Solution pH measurement method: pH meter.

[0137] Method for determining ammonia content: Nessler's reagent spectrophotometry.

[0138] Instant solubility test method: Take 10g of collagen at room temperature, add 50mL of water, and stir with a glass rod until the solution becomes clear.

[0139] Chromium content determination method: Weigh 0.5g of collagen, decompose the sample by dry ashing, and then determine its chromium content using an atomic absorption spectrometer.

[0140] Ash content determination method: Accurately weigh 5.000g of collagen, first ashing it on an electric furnace until no smoke is emitted, then transferring it to a muffle furnace and calcining it at 550℃ for 4 hours until constant weight is achieved, and then weighing it to obtain the ash content.

[0141] Bulk density determination method: Weigh 50.00g of collagen into a graduated cylinder, measure its volume, and then obtain the bulk density by dividing the mass by the volume.

Claims

1. A material for use in a dechroming and deaminating agent for a collagen solution containing chromium, characterized in that, The materials used in the chromium removal and ammonia reduction agent are composed of chromium ion replacement materials, electrostatic adsorption materials, ammonia reduction materials, magnetic materials, and coating materials. The electrostatic adsorption material preparation method uses one of the following materials as a carrier: kaolinite, montmorillonite, diatomite, and magnesium silicate. One of these materials is selected and modified through the following series of processes. a2) Activation treatment of the carrier: Weigh 40g of one of the above carriers, add 400mL of 0.75~1.25mol / L hydrochloric acid solution, ultrasonically disperse for 20~30min, react at 60~80℃ for 5~6h, filter, wash until neutral, dry, and obtain the activated carrier; b2) Add 20g of the activated carrier from step a2) to a three-necked flask containing 80-100mL of toluene, sonicate for 15-20min, and under the protection of nitrogen flow rate of 60-80 mL / min, slowly raise the temperature of the mixed solution to 105-110℃, add 3-5g of 3-aminopropyltriethoxysilane, continue stirring for 12-15h, then filter, wash, purify with anhydrous ethanol for 12-15h, and vacuum dry at 70-80℃ for 12-15h to obtain the activated carrier-APTES. c2) Under nitrogen protection, 50-60 mL of dichloromethane and 0.025-0.035 mol of EDTA were transferred, and 2-3 mL of thionyl chloride was added dropwise under constant pressure. Then, 1 g of the activated support - APTES from step b2) was quickly added. The reaction was carried out at room temperature for 2-3 h. After filtration, the mixture was washed with 8 mL of dichloromethane, 8 mL of acetone, 10 mL of deionized water, 10 mL of 0.15-0.25 mol / L sodium bicarbonate aqueous solution, and 10 mL of deionized water. The mixture was then dried at 50-60 °C to obtain the electrostatic adsorption material. The preparation method of the magnetic material: a4) Add 20-30 mL of deionized water to 70-80 mL of ethylene glycol and stir. Then add 32.0 g of isobutanolamine and 6.0-7.0 g of diethanolamine and stir for 5-10 min to obtain solution A2. b4) Dissolve 3.0g FeCl2·4H2O in 30~40mL of deionized water, then add 60~70mL of ethylene glycol while stirring to obtain solution B2; c4) Add 20-30 mL of deionized water to 70-80 mL of ethylene glycol, then add 5.0 g of FeCl3·6H2O, and stir for 5 min to obtain solution C2; d4) Divide solution A2 into two equal parts, mix one part with solution B2, and mix the other part with solution C2; e4) Mix the two solutions and stir for 20-30 minutes, then pour them into a polyimide liner, cover and seal with tape, place in an oven at 90-100℃ for 5-10 hours, cool naturally to room temperature, separate the black product with a magnet, wash with 100-150 mL of deionized water, then wash 2-4 times with 100-150 mL of anhydrous ethanol, and dry in an oven at 30-40℃ for 6-12 hours to obtain the magnetic material iron(III) oxide.

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