A method for preparing iodine adsorbing material by using chrome leather scraps

Abstract

This invention relates to a method for preparing iodine adsorbent materials using chromium leather scraps. The method uses chromium leather scraps as raw material, which are activated with alkali at 20-60°C for 2-10 hours. Then, a nitrogen-containing modifier and a dialdehyde crosslinking agent are added to the activated chromium leather scrap dispersion, and the mixture is stirred at 20-60°C for 4-12 hours. After filtration and drying, the iodine adsorbent material is obtained. This method grafts nitrogen-containing groups onto the collagen fibers of chromium leather scraps via a Schiff base reaction using a dialdehyde crosslinking agent, endowing them with a large number of active sites, giving them good adsorption capacity and stability, and enabling efficient adsorption in various iodine pollution scenarios (gaseous iodine, aqueous iodine). This method not only solves the problem of chromium leather scrap disposal but also provides a low-cost solution for the treatment of radioactive iodine pollution, aligning with the circular economy and green development concept of "using waste to treat waste." The process of this invention is simple, with no toxic reagent emissions, readily available and inexpensive raw materials, and is easy to scale up.

Description

Technical Field

[0001] This invention relates to the field of iodine adsorption materials and the resource utilization technology of leather solid waste, specifically to a method for preparing iodine adsorption materials by grafting nitrogen-containing functional groups onto chromium leather scraps. Background Technology

[0002] Radioactive iodine exists primarily in isotopic form, among which long-lived ¹² 9 Nuclear-grade I (half-life 15.7 million years) and short-lived, highly toxic ¹³¹I (half-life 8.02 days) are the core targets of environmental governance. Their sources include: 1) Nuclear industry-related emissions: during the nuclear fuel cycle (especially spent fuel reprocessing),²³ 9 Pu and 23 5 U fission releases a large amount of radioactive iodine isotopes, mainly in the form of gaseous I2 and CH3I, and may also enter the aquatic environment through wastewater leakage; 2) Nuclear accident emergency scenario: In the event of a serious accident at a nuclear power plant, the leakage of radioactive materials from the reactor will release nuclides such as ¹³¹I into the atmosphere and water bodies, forming radioactive plumes that spread and pollute; 3) Generation from nuclear medicine applications: With the rapid development of nuclear medicine, the iodine-containing wastewater generated by medical activities such as the treatment of differentiated thyroid cancer using ¹³¹I has increased exponentially, becoming an important source of low-level radioactive wastewater.

[0003] The dangers of radioactive iodine stem from its high mobility, bioaccumulation, and radioactivity. For example, when humans ingest radioactive iodine through food or inhalation, it rapidly accumulates in the thyroid gland, causing thyroiditis, hypothyroidism, and potentially thyroid cancer in the long term;¹² 9 I has an extremely long half-life, allowing it to remain in the environment for extended periods and accumulate through the food chain, posing a persistent threat to ecosystems. While ¹³¹I has a shorter half-life, it delivers high radiation doses in the short term, making it prone to causing regional pollution events. In nuclear medicine treatment, ¹³¹I treatment of brain metastases may cause complications such as cerebral edema, and improper treatment of its medical wastewater can directly pollute the aquatic environment.

[0004] Currently, technologies for treating radioactive iodine include chemical precipitation, adsorption, membrane separation, biological treatment, photocatalytic oxidation, and electrochemical methods. Among these, adsorption has become a research hotspot due to its simplicity, high efficiency, and wide applicability, especially in the capture of gaseous iodine and the deep purification of low-level radioactive wastewater. In recent years, various types of novel high-performance adsorption materials have been developed. For example, silver-based adsorbents such as silver-exchanged zeolite and silver-supported mesoporous silica achieve chemical adsorption through the formation of AgI precipitate, exhibiting high adsorption selectivity. However, silver is expensive and difficult to regenerate. Carbon-based adsorbents such as activated carbon and carbon nanotubes, after functionalization with amino and sulfur groups, show significantly improved adsorption capacity. However, their adsorption is mainly physical, and they are prone to desorption under high temperature or humidity conditions. Rare earth-based composite adsorbents such as rare earth-aluminum oxide clusters and rare earth organic frameworks (REOFs) have good adsorption effects and excellent recyclability, but their preparation processes are complex and costly, making industrial application difficult. Novel porous adsorbents such as covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) can construct specific pore structures through molecular design, tune rich active sites to achieve high adsorption capacity, and utilize covalent bonding to enhance adsorption stability. They are suitable for the selective capture of iodine in complex systems. However, the synthesis cost of these materials is high, and their structural stability under harsh environments such as high humidity and strong radiation still faces challenges, creating bottlenecks for large-scale preparation and application. Therefore, seeking adsorption materials that combine high adsorption efficiency, excellent stability, low cost, and ease of industrialization has become one of the important research directions in the field of radioactive iodine capture.

[0005] Chrome leather scraps are chromium-containing solid waste generated during the shaving process in leather tanning to adjust the thickness of chrome-tanned wet leather. As the world's largest producer and consumer of leather, my country accounts for a quarter of global leather production and generates up to 1.4 million tons of solid waste annually from leather tanning, of which approximately 280,000 tons (20%) are chromium-containing leather scraps. Statistics show that leather tanneries incur nearly 1,000 yuan in costs for treating one ton of chromium leather scraps, making it a major source of environmental pressure for these enterprises. In particular, in 2016, my country's Ministry of Environmental Protection included chromium-containing waste from the leather industry (including chromium leather scraps) in the "National Hazardous Waste List," prohibiting direct landfilling and incineration, further highlighting the urgency of its standardized treatment.

[0006] Chromium leather scraps contain two main components—collagen and chromium. To achieve full recycling of these two components, the current treatment methods and resource utilization technologies for chromium leather scraps mainly include the following four aspects: (1) Regenerated leather preparation. Chromium leather scraps are crushed into collagen fibers, combed and shaped into fiber pads, modified with macromolecular crosslinking agents, and then dehydrated, dried and hot-pressed to prepare regenerated leather. The added value of this product is very low, and it only occupies a certain share in the low-to-mid-end leather products market. (2) Protein resource recycling and utilization. For example, the collagen in chromium leather scraps can be converted into amino acids through hydrolysis technology and used as fertilizer and soil conditioner; the collagen hydrolysis products recovered from chromium leather scraps can be used to prepare industrial additives such as surfactants, industrial adhesives, and cement foaming agents, or chemically modified synthetic leather retanning fillers, waterproofing agents, etc., to realize the resource cycle of the leather making process. However, this strategy of extracting protein products from chromium leather scraps and then reusing them mainly has the disadvantages of complex process, secondary pollution, chromium residue and low added value of products. (3) Chromium resource recycling and reuse. For example, chromium can be removed from chromium leather scraps by acid hydrolysis, alkaline hydrolysis, or enzymatic hydrolysis. The recovered chromium hydroxide can be used to prepare chromium tanning agents and reused in the leather tanning process, which can reduce the consumption of fresh chromium tanning agents. However, these methods also have the drawbacks of complex processes, secondary pollution, and unstable product quality. (4) Energy conversion and basic material conversion. For example, chromium leather scraps can be pyrolyzed under anaerobic conditions to produce biomass fuel gas, biochar, and tar. Biochar can be used as an adsorbent or soil conditioner, and the fuel gas can be used for heating and power generation. Chromium leather scraps can be combined with inorganic fillers and sintered at high temperature to prepare ceramics, glass ceramics, and other materials. Chromium can be used as a modifier to improve the mechanical properties of the materials. However, the limitation of these methods is that the energy utilization process requires strict control of chromium volatilization pollution, and the added value of inorganic material conversion is low.

[0007] Based on the above analysis, it can be seen that there are currently various technologies for the treatment and resource utilization of chrome leather scraps, demonstrating certain environmental and economic benefits. However, existing technologies still suffer from problems such as low product added value, limited high-end applications, secondary pollution, and difficulties in large-scale production. Therefore, it is necessary to focus on the research and development of high-value functional materials based on chrome leather scraps, strengthen the integration of clean production technologies and multiple technologies, promote cross-industry collaboration, and achieve a complete transformation of chrome leather scraps from "hazardous waste" to "green resource," providing strong support for the green transformation and circular economy development of the leather industry. Summary of the Invention

[0008] This invention addresses the dual bottlenecks in the research and development of iodine adsorbent materials and the treatment and resource utilization of chromium leather scraps. It utilizes chromium leather scraps, a solid waste from the leather industry, as a raw material to prepare high-value-added radioactive iodine adsorbent materials with high adsorption capacity, excellent stability, low cost, and ease of industrialization. The basic idea of ​​this invention is that the collagen fibers abundant in chromium leather scraps, as a natural polymer material, possess a unique helical structure and rich active functional groups (-OH, -COOH, -NH2, -CONH2, etc.) and trivalent chromium ions, providing a high-quality biomass raw material for the green preparation of iodine adsorbent materials. Utilizing chromium leather scrap collagen fibers to prepare iodine adsorbent materials not only achieves the high-value transformation of chromium leather scraps, a solid waste from the leather industry, but also provides a low-cost, environmentally friendly solution for iodine pollution control, aligning with the circular economy concept of "treating waste with waste." Considering the dense structure, small specific surface area, and numerous encapsulated active groups in the collagen fibers of chrome leather scraps, resulting in limited adsorption capacity when applied directly, this invention first disrupts the hydrogen bond network within the collagen fibers through mild alkali treatment, causing partial unwinding and significantly increasing the specific surface area, thus exposing more active sites such as -OH and -NH2. Furthermore, to further enhance the adsorption capacity of chrome leather scrap collagen fibers for iodine, this invention uses a compound with abundant nitrogen atoms and lone pair electrons as a modifier. This compound is grafted onto the collagen fibers via a Schiff base reaction, significantly increasing the nitrogen content of the collagen fibers and providing them with numerous iodine adsorption sites, thereby significantly improving the iodine adsorption capacity of the chrome leather scrap collagen fiber adsorbent material.

[0009] The adsorption mechanism of iodine by the chromium leather scrap collagen fiber adsorbent material prepared in this invention is as follows: (1) The active functional groups (-OH, -COOH, -NH2, -CONH2, etc.) on the chromium leather scrap collagen fiber can adsorb iodine (such as I2 and I3) through electrostatic interaction and hydrogen bonding. - (1) Adsorption occurs, and on the other hand, the benzene rings contained in the collagen fibers can achieve π-π stacking through π bonds; (2) According to the Lewis acid-base theory, I2 is a Lewis acid, and a large number of nitrogen / oxygen atoms with lone pairs of electrons on the grafted chromium leather scrap collagen fibers are Lewis bases. Through acid-base interaction, lone pairs of electrons are transferred to I2 and I3. - On top, they form a shared electron pair, thereby achieving control over I2 and I3. - (3) The trivalent chromium ions contained in the chromium leather scraps can be chemically adsorbed by forming iodine-containing chromium salts, which further improves the iodine adsorption performance of the adsorption material of the present invention.

[0010] To achieve the above objectives, the present invention aims to provide a method for preparing iodine adsorbent materials using chromium leather scraps, comprising the following steps: Step 1: Disperse chrome leather scraps in water, gradually add alkaline solution to adjust the pH to 10-14, then stir at 20-60℃ for 2-10 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Take the activated chrome leather scraps, add water, a nitrogen-containing modifier, and a dialdehyde crosslinking agent, stir at 20-60℃ for 4-12 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material; In this method, the chrome leather scraps are dispersed in water, wherein the mass ratio of the chrome leather scraps to water is 1:(10-50); The alkali used to activate the chrome leather scraps in this method is any one of sodium hydroxide or potassium hydroxide; In the modification of the chrome leather scraps in this method, the mass ratio of the activated chrome leather scraps to water is 1:(10-50). The mass ratio of the activated chromium leather scraps to the nitrogen-containing modifier is 1:(0.3~4); the nitrogen-containing modifier in this method is any one of melamine, 1,2,4-triazine, 1,2,3-triazine, 1,3,5-triazine, and polyethyleneimine; the dialdehyde crosslinking agent in this method is selected from any one of glutaraldehyde, glyoxal, dialdehyde carboxymethyl cellulose, and dialdehyde starch; in the modification of the chromium leather scraps in this method, when the dialdehyde crosslinking agent is glutaraldehyde or glyoxal, the volume concentration of the dialdehyde crosslinking agent in the entire reaction system is controlled to be 2%~12%; when the dialdehyde crosslinking agent is dialdehyde carboxymethyl cellulose or dialdehyde starch, the mass concentration of the dialdehyde crosslinking agent in the entire reaction system is controlled to be 4%~24%.

[0011] The present invention provides a method for preparing iodine adsorbent materials using chromium leather scraps, which has the following advantages: First, this invention transforms chromium leather scraps into iodine adsorbent materials, replacing traditional landfill / incineration, significantly reducing the risk of chromium pollution in soil and groundwater. It not only solves the problem of disposing of hazardous solid waste such as chromium leather scraps, but also provides a low-cost solution for the treatment of radioactive iodine pollution, which is in line with the circular economy and green development concept of "treating waste with waste".

[0012] Secondly, compared with iodine adsorbent materials such as activated carbon and MOFs, the chromium leather scrap-based iodine adsorbent material prepared by this invention does not require the consumption of fossil resources, the preparation process has no toxic reagent emissions, and has the advantages of low cost and high added value conversion.

[0013] Third, the iodine adsorbent material prepared by the present invention using chromium leather scraps retains the hydrophilic / lipophilic properties of natural collagen fibers and has stable performance, making it suitable for various iodine pollution scenarios (gaseous iodine, aqueous iodine).

[0014] Fourth, the process of preparing iodine adsorbent material using chromium leather scraps is simple, the raw materials are readily available and inexpensive, and it is easy to carry out large-scale preparation. Detailed Implementation

[0015] The following embodiments are provided to illustrate the present invention in more detail. It should be noted that the following embodiments should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above description of the present invention are still within the scope of protection of the present invention.

[0016] Example 1 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:20), gradually add sodium hydroxide solution to adjust the pH to 12, then stir at 45℃ for 6 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:20), then add melamine (the mass ratio of activated chrome leather scraps to water is 1:1) and glutaraldehyde (volume concentration of 8%), stir at 45℃ for 6 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0017] Example 2 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:50), gradually add potassium hydroxide solution to adjust the pH to 10, then stir at 25℃ for 10 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:10), then add 1,2,4-triazine (the mass ratio of activated chrome leather scraps to water is 1:2) and glyoxal (volume concentration of 12%), stir at 30℃ for 10 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0018] Example 3 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:10), gradually add sodium hydroxide solution to adjust the pH to 14, then stir at 20℃ for 5 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:50), then add 1,2,3-triazine (the mass ratio of activated chrome leather scraps to activated chrome leather scraps is 1:3) and dialdehyde carboxymethyl cellulose (mass concentration of 12%), stir at 20℃ for 12 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0019] Example 4 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:35), gradually add potassium hydroxide solution to adjust the pH to 11, then stir at 60℃ for 2 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:30), then add 1,3,5-triazine (the mass ratio of activated chrome leather scraps to activated chrome leather scraps is 1:4) and dialdehyde starch (mass concentration of 4%), stir at 40℃ for 8 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0020] Example 5 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:15), gradually add sodium hydroxide solution to adjust the pH to 13, then stir at 35℃ for 8 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:40), then add polyethyleneimine (the mass ratio of activated chrome leather scraps to water is 1:0.3) and glutaraldehyde (volume concentration of 2%), stir at 60℃ for 4 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0021] Example 6 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:30), gradually add potassium hydroxide solution to adjust the pH to 12, then stir at 50℃ for 4 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:25), then add melamine (the mass ratio of activated chrome leather scraps to activated chrome leather scraps is 1:1.5) and glyoxal (volume concentration of 10%), stir at 35℃ for 9 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0022] Example 7 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:40), gradually add sodium hydroxide solution to adjust the pH to 10, then stir at 30℃ for 9 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:15), then add 1,2,4-triazine (the mass ratio of activated chrome leather scraps to activated chrome leather scraps is 1:2.5) and dialdehyde carboxymethyl cellulose (mass concentration of 24%), stir at 25℃ for 7 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0023] Example 8 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:25), gradually add potassium hydroxide solution to adjust the pH to 11, then stir at 40℃ for 7 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:35), then add 1,2,3-triazine (the mass ratio of activated chrome leather scraps to activated chrome leather scraps is 1:3.5) and dialdehyde starch (mass concentration of 16%), stir at 55℃ for 5 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0024] Example 9 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:45), gradually add sodium hydroxide solution to adjust the pH to 13, then stir at 55℃ for 3 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:45), then add 1,3,5-triazine (the mass ratio of activated chrome leather scraps to activated chrome leather scraps is 1:2.8) and glutaraldehyde (volume concentration of 7%), stir at 50℃ for 11 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0025] Example 10 Step 1: Disperse chrome leather scraps in water (the mass ratio of chrome leather scraps to water is 1:32), gradually add potassium hydroxide solution to adjust the pH to 14, then stir at 28℃ for 3 hours, wash with water until neutral, filter, and dry to obtain activated chrome leather scraps; Step 2: Disperse activated chrome leather scraps in water (the mass ratio of activated chrome leather scraps to water is 1:28), then add polyethyleneimine (the mass ratio of activated chrome leather scraps to activated chrome leather scraps is 1:3.2) and dialdehyde carboxymethyl cellulose (mass concentration of 10%), stir at 37℃ for 8 hours, filter, and dry to obtain chrome leather scrap-based iodine adsorbent material.

[0026] For the chromium leather scrap-based iodine adsorbent material prepared in the above embodiments, the ultraviolet-visible absorption spectrum of the iodide ion solution was measured by ultraviolet-visible spectrophotometry, and a standard curve was plotted. The removal rate of iodide ions (I3I ions) was calculated based on the standard curve. - The initial concentration was 100 mg / L; the adsorption capacity of the chromium leather scrap-based iodine adsorbent material for iodine vapor was determined by gravimetric method, and the results are shown in Table 1.

[0027] Table 1

Claims

1. A method for preparing iodine adsorbent materials using chromium leather scraps, characterized in that, include: 1) Activation of chrome leather scraps; 2) Modification of chrome leather scraps: Take activated chrome leather scraps, add water, nitrogen-containing modifier and dialdehyde crosslinking agent, stir at 20~60℃ for 4~12 hours, filter, dry to obtain chrome leather scrap-based iodine adsorbent material.

2. The method for preparing iodine adsorbent material using chromium leather scraps according to claim 1, characterized in that, The activation of the chrome leather scraps includes: dispersing the chrome leather scraps in water, gradually adding an alkaline solution to adjust the pH to 10-14, stirring at 20-60°C for 2-10 hours, washing with water until neutral, filtering, and drying to obtain the activated chrome leather scraps.

3. The method for preparing iodine adsorbent material using chromium leather scraps according to claim 2, characterized in that, The process involves dispersing chromium leather scraps in water, wherein the mass ratio of the chromium leather scraps to water is 1:(10~50).

4. The method for preparing iodine adsorbent material using chromium leather scraps according to claim 2, characterized in that, The alkali used to activate chrome leather scraps is either sodium hydroxide or potassium hydroxide.

5. The method for preparing iodine adsorbent material using chromium leather scraps according to claim 1, characterized in that, In the modification of the chromium leather scraps, the mass ratio of the activated chromium leather scraps to water is 1:(10~50), and the mass ratio of the activated chromium leather scraps to the nitrogen-containing modifier is 1:(0.3~4).

6. The method for preparing iodine adsorbent material using chromium leather scraps according to claim 1, characterized in that, The nitrogen-containing modifier is any one of melamine, 1,2,4-triazine, 1,2,3-triazine, 1,3,5-triazine, and polyethyleneimine; the dialdehyde crosslinking agent is any one of glutaraldehyde, glyoxal, dialdehyde carboxymethyl cellulose, and dialdehyde starch.

7. The method for preparing iodine adsorbent material using chromium leather scraps according to claims 1 and 6, characterized in that, In the modification of the chrome leather scraps, when the dialdehyde crosslinking agent is glutaraldehyde or glyoxal, the volume concentration of the dialdehyde crosslinking agent in the entire reaction system is controlled to be 2%~12%; when the dialdehyde crosslinking agent is dialdehyde carboxymethyl cellulose or dialdehyde starch, the mass concentration of the dialdehyde crosslinking agent in the entire reaction system is controlled to be 4%~24%.

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