阅读说明：本技术 一种缓释型砷固定剂及其制备方法和在砷污染土壤修复中的应用 (Slow-release arsenic fixing agent, preparation method thereof and application thereof in arsenic-contaminated soil remediation ) 是由 李栎 王豪 文波 雷国建 史勇 刘朝 马英才 于 2021-09-23 设计创作，主要内容包括：本发明公开了一种缓释型砷固定剂及其制备方法和在砷污染土壤修复中的应用。将香兰素加入至溶有壳聚糖的醋酸溶液中进行缩合反应,得到香兰素改性壳聚糖；将粉煤灰与高岭土混合后,进行焙烧处理,得到吸附材料；将吸附材料与硫化钙粉末及赤泥粉末混合后,进行振荡处理,得到砷固定剂；将砷固定剂与香兰素改性壳聚糖混合后,进行热融处理,冷却,制粒,得到缓释型砷固定剂。该缓释型砷固定剂可以通过吸附和化学反应等方式实现污染土壤中砷的高效固定,修复后的砷污染土壤中砷浸出毒性达到GB 14848-2017Ⅲ类标准,且该缓释型砷固定剂可以缓慢释放固定砷的活性物质,使得对土壤中砷的固定作用持久,长期有效。(The invention discloses a slow-release arsenic fixing agent, a preparation method thereof and application thereof in arsenic-polluted soil remediation. Adding vanillin into acetic acid solution dissolved with chitosan for condensation reaction to obtain vanillin modified chitosan; mixing the fly ash and kaolin, and then roasting to obtain an adsorbing material; mixing the adsorption material with calcium sulfide powder and red mud powder, and then carrying out oscillation treatment to obtain an arsenic fixing agent; mixing the arsenic fixing agent and vanillin modified chitosan, performing hot melting treatment, cooling, and granulating to obtain the slow-release arsenic fixing agent. The slow-release arsenic fixing agent can realize efficient fixation of arsenic in the polluted soil through adsorption, chemical reaction and other modes, the leaching toxicity of the arsenic in the repaired arsenic-polluted soil reaches GB 14848-2017 III standard, and the slow-release arsenic fixing agent can slowly release active substances for fixing the arsenic, so that the fixing effect on the arsenic in the soil is durable and effective for a long time.)

1. A preparation method of a slow-release arsenic fixing agent is characterized by comprising the following steps: the method comprises the following steps:

1) adding vanillin into acetic acid solution dissolved with chitosan for condensation reaction to obtain vanillin modified chitosan;

2) mixing the fly ash and kaolin, and then roasting to obtain an adsorbing material;

3) mixing the adsorption material with calcium sulfide powder and red mud powder, and then carrying out oscillation treatment to obtain an arsenic fixing agent;

4) mixing the arsenic fixing agent and vanillin modified chitosan, performing hot melting treatment, cooling, and granulating to obtain the slow-release arsenic fixing agent.

2. The method for preparing the slow-release arsenic fixing agent according to claim 1, wherein the method comprises the following steps: the mass of the vanillin is 50-100% of that of the chitosan.

3. The method for preparing the slow-release arsenic fixing agent according to claim 1, wherein the method comprises the following steps: the conditions of the condensation reaction are as follows: the temperature is 50-80 ℃ and the time is 0.5-2 h.

4. The method for preparing the slow-release arsenic fixing agent according to claim 1, wherein the method comprises the following steps: the mass ratio of the fly ash to the kaolin is 50-70: 30-50.

5. The method for preparing the slow-release arsenic fixing agent according to claim 1, wherein the method comprises the following steps: the roasting treatment conditions are as follows: the temperature is 600-800 ℃, and the time is 1-4 h.

6. The method for preparing the slow-release arsenic fixing agent according to claim 1, wherein the method comprises the following steps: the mass ratio of the adsorption material to the calcium sulfide powder to the red mud powder is as follows: 5-20: 1-5: 75-94.

7. The method for preparing the slow-release arsenic fixing agent according to claim 1, wherein the method comprises the following steps: the conditions of the oscillation treatment are as follows: the oscillation frequency is 300-400 rpm, and the time is 1-2 h.

8. The method for preparing the slow-release arsenic fixing agent according to claim 1, wherein the method comprises the following steps: the mass ratio of the arsenic fixing agent to the vanillin modified chitosan is 85-95: 5-15.

9. A slow-release arsenic fixing agent is characterized in that: the preparation method of any one of claims 1 to 8.

10. The use of a slow-release arsenic fixing agent as claimed in claim 9, wherein: the method is applied to the remediation of the arsenic-polluted soil.

Technical Field

The invention relates to an arsenic fixing agent, in particular to a slow-release arsenic fixing agent, a preparation method thereof and application of the slow-release arsenic fixing agent in arsenic-polluted soil remediation, and belongs to the technical field of arsenic-polluted soil remediation.

Background

In recent years, the industrialization and urbanization of China are continuously promoted, and the problem of soil pollution is increasingly serious. Soil is one of the important natural resources on which human beings live, and is also an important component of the human ecological environment. With the aggravation of industrial and urban pollution, pollutants containing heavy metals enter soil through various ways, and the corresponding heavy metal elements in the soil are enriched. Heavy metal pollution has the characteristics of concealment, long-term property and irreversibility. The work of preventing and controlling heavy metal pollution is the central importance of the environmental protection work in China. Due to the wide application of arsenic in many industries, arsenic is remained in soil in large quantity through the processes of mining, processing, using, abandoning and the like, so that the arsenic pollution in the soil is ubiquitous worldwide.

The remediation of the heavy metal contaminated soil mainly comprises an engineering physical and chemical method and a biological remediation method. The engineering physical and chemical methods comprise a soil-covering method, a washing complexing method, an electrokinetic chemical method, a heat treatment method and the like, and are not suitable for the soil with large polluted area. The bioremediation method comprises phytoremediation, microbial remediation, animal remediation and the like, and the phytoremediation and low-grade animal remediation method has a less obvious effect on soil remediation; the microorganism remediation utilizes the effects of absorption, precipitation, oxidation, reduction and the like of certain microorganisms in the soil on heavy metals, so that the toxicity of the heavy metals in the soil is reduced. The technology has little influence on the surrounding environment, does not produce secondary pollution and has huge soil remediation potential. However, the existing microbial remediation technology for heavy metal contaminated soil has certain limitations, such as long duration and slow effect of microbial remediation, and generally forms a complex to reduce the harm of heavy metals, and the heavy metals cannot be removed from the soil.

Chinese patent literature discloses a preparation and use method (CN201610071104.0) of a slow-release iron-based biochar soil heavy metal passivator, which adopts iron-based biochar, kaolin and biological starch as core materials, takes acid silica sol and chitosan solution composite materials as coating films, and prepares the core materials and the films into the passivator suitable for treating cadmium and arsenic compound polluted farmlands. The passivator prepared by the method can passivate cadmium and arsenic at the same time, has a slow release effect, and can be effective on heavy metals for a long time. However, the passivator is mainly suitable for paddy fields, the pollution degree of heavy metals such as arsenic in the soil of the paddy fields is almost not high, and the passivator has unknown passivation effect on other polluted fields.

Chinese patent literature discloses a repairing agent, a preparation method thereof and a method (CN201711076050.8) for repairing heavy metal contaminated soil by using the repairing agent, wherein the repairing agent is prepared by using biochar, sepiolite, monocalcium phosphate, sugarcane residue, lime powder, longan peel, tartaric acid, hydroxyethylidene triphosphonic acid, potassium lignosulphonate, malic acid, chitosan and legume root straw as raw materials, and can synchronously remove mercury, cadmium, lead, arsenic and pyrene in the contaminated soil. However, the raw material components required by the production of the repairing agent are complex, the sources are not easy to obtain, and the industrial production is difficult to realize.

Disclosure of Invention

Aiming at the prior art, the first purpose of the invention is to provide a slow-release arsenic fixing agent for arsenic-polluted soil remediation, the slow-release arsenic fixing agent can realize efficient fixation of arsenic in the polluted soil through adsorption, chemical reaction and other modes, the leached toxicity of arsenic in the repaired polluted soil reaches the III-type standard of underground water quality standard (GB 14848-2017), and the slow-release arsenic fixing agent can slowly release active substances for fixing arsenic, so that the fixation effect on arsenic in the soil is durable and effective for a long time.

The second purpose of the invention is to provide a preparation method of the slow-release arsenic fixing agent for arsenic-contaminated soil, which is simple, low in raw material cost and beneficial to large-scale production.

The third purpose of the invention is to provide an application of the slow-release arsenic fixing agent in arsenic-polluted soil remediation, the slow-release arsenic fixing agent is added into arsenic-polluted soil, active ingredients acting on arsenic can be slowly released, the long-term effectiveness of the arsenic fixing effect in the soil can be ensured, the utilization rate of the arsenic fixing agent is improved, the problems of agglomeration and low utilization rate caused by one-time release of the arsenic fixing agent are avoided, and the arsenic leaching toxicity in the repaired arsenic-polluted soil reaches the III-class standard of underground water quality standard (GB 14848-.

In order to achieve the technical purpose, the invention provides a preparation method of a slow-release arsenic fixing agent, which comprises the following steps:

1) adding vanillin into acetic acid solution dissolved with chitosan for condensation reaction to obtain vanillin modified chitosan;

2) mixing the fly ash and kaolin, and then roasting to obtain an adsorbing material;

3) mixing the adsorption material with calcium sulfide powder and red mud powder, and then carrying out oscillation treatment to obtain an arsenic fixing agent;

4) mixing the arsenic fixing agent and vanillin modified chitosan, performing hot melting treatment, cooling, and granulating to obtain the slow-release arsenic fixing agent.

Preferably, the mass of the vanillin is 50 to 100 percent of the mass of the chitosan. Vanillin is mainly used for modifying a large number of phenolic hydroxyl groups in chitosan by condensing aldehyde groups of vanillin with amino groups in chitosan, wherein the phenolic hydroxyl groups in vanillin have methoxyl groups at ortho positions, and have higher arsenic ion coordination and adsorption capacity compared with common hydroxyl groups or phenolic hydroxyl groups, so that the arsenic ion adsorption capacity of chitosan can be improved by modifying the chitosan with vanillin. If the using amount of the vanillin is too low, the modified vanillin amount on the chitosan is too low, and the modification effect cannot be achieved, and if the using amount of the vanillin is too high, the modification amount of the vanillin cannot be further improved due to the limited number of the active amino groups of the chitosan.

As a preferred embodiment, the condensation reaction conditions are: the temperature is 50-80 ℃ and the time is 0.5-2 h.

Preferably, the mass ratio of the fly ash to the kaolin is 50-70: 30-50. The fly ash is a product obtained after burning coal, has a porous structure and has a good adsorption effect on arsenic, the kaolin is a layered silicate mineral and has a good adsorption property, and the kaolin has a good water retention property. And the fly ash and the kaolin are easily available raw materials, particularly the fly ash has certain harm to the environment, and the fly ash is used as a raw material for producing the arsenic fixing agent, so that the resource recycling is facilitated. If the proportion of the kaolin is too high, the arsenic adsorption performance of the adsorption material is reduced, and too low, the loss of water in soil is large, local agglomeration is caused, and effective contact between the medicament and the polluted soil is reduced.

As a preferred embodiment, the conditions of the roasting treatment are as follows: the temperature is 600-800 ℃, and the time is 1-4 h. If the temperature is too low, the fly ash and the kaolin are difficult to be fully activated, and if the temperature is too high, energy is wasted.

Preferably, the mass ratio of the adsorbing material to the calcium sulfide powder to the red mud powder is 5-20: 1-5: 75-94. The calcium sulfide powder can provide active sulfur ions to form stable sulfides with arsenic, the red mud contains high-content iron which can react with the arsenic to generate low-mobility ferric arsenate, the three are combined according to a proper proportion for use, the organic combination of physical adsorption and chemical reaction for fixing the arsenic can be realized, and particularly, the porous structure of the adsorption material can contain active ingredients acting on the arsenic, such as the calcium sulfide powder and the red mud powder, and can play a role in slow release. The red mud is used as industrial solid waste, the discharge amount is large, the pollution to the environment is more and more serious, the resource utilization of the red mud to the maximum extent is reluctant, and the slow-release arsenic fixing agent adopts the red mud as a raw material, so that the waste treatment by waste is realized, and the environmental risk is reduced.

As a preferable mode, the conditions of the oscillation treatment are as follows: the oscillation frequency is 300-400 rpm for 1-2 h. Through high-frequency oscillation, the materials can be mixed more uniformly, and meanwhile, active ingredients such as calcium sulfide powder and red mud powder which can act with arsenic can enter gaps of the adsorption materials, so that the slow-release effect can be improved.

Preferably, the mass ratio of the arsenic fixing agent to the Lanxin-modified chitosan is 85-95: 5-15. When the dosage of the vanillin modified chitosan is too low, the binding molding is difficult, the slow release effect cannot be realized, and when the dosage is too high, the arsenic fixing agent is difficult to effectively release.

The acetic acid solution dissolved with chitosan is prepared from chitosan and an acetic acid solution with pH of 5-7 according to a liquid-solid ratio of 10-20 mL: 1g of the above-mentioned components were mixed. The acetic acid solution is used as a cosolvent for dissolving the chitosan on one hand and as a catalyst for condensation reaction on the other hand.

The adsorbing material is ground to 50-100 meshes.

The red mud powder is obtained by drying red mud at the temperature of 95-105 ℃ and grinding the dried red mud to 200-400 meshes.

The particle size of the slow-release arsenic fixing agent is 3-5 mm.

The invention also provides a preparation method of the slow-release arsenic fixing agent for arsenic-contaminated soil, which is obtained by the preparation method. The slow-release arsenic fixing agent provided by the invention is obtained by compounding vanillin modified chitosan, an adsorption material, calcium sulfide powder and red mud powder, wherein the vanillin modified chitosan is used as a good adhesive and can wrap and adhere the particles to form a granular material, meanwhile, the vanillin modified chitosan contains a large number of polar groups, particularly, a large number of phenolic hydroxyl groups are modified by vanillin, so that the vanillin modified chitosan can generate chelate adsorption with arsenic ions, the calcium sulfide powder and the red mud powder contain active iron ions and active sulfur negative ions and can act on the arsenic ions through chemical reaction and other modes, the adsorption material is a roasted product of fly ash and kaolin, is a porous structure material and has strong adsorption capacity, and after the components are compounded, a good synergistic effect is achieved on the stabilization and fixing effect of free arsenic ions in soil, the vanillin modified chitosan can be chelated with free arsenic ions in soil for adsorption and enrichment, the red mud, calcium sulfide and the adsorbing material coated in the vanillin modified chitosan are released together with slow dissolution of the vanillin modified chitosan, the red mud, the calcium sulfide and the like can convert the enriched arsenic ions into insoluble matters such as arsenic sulfide, ferric arsenate precipitate and the like, and the insoluble matters are adsorbed and coated by the adsorbing material, so that the mobility of heavy metal arsenic is greatly reduced.

The invention also provides application of the slow-release arsenic fixing agent, which is applied to remediation of arsenic-polluted soil.

Compared with the prior art, the technical scheme of the invention has the following beneficial technical effects:

(1) the slow-release arsenic fixing agent provided by the invention is used for repairing arsenic-polluted soil, the arsenic leaching toxicity reaches the III-type standard of underground water quality standard (GB 14848-2017), and the arsenic leaching toxicity of the repaired arsenic-polluted soil is less than 1 mg/L.

(2) The slow-release arsenic fixing agent provided by the invention adopts solid wastes such as red mud and fly ash as raw materials, is low in cost, realizes resource utilization, and achieves the purpose of treating wastes with processes of wastes against one another.

(3) The slow-release arsenic fixing agent provided by the invention has a slow-release effect, can slowly release the arsenic fixing agent in a soil environment, can ensure that the arsenic fixing agent has long-term effectiveness on arsenic in soil, and can effectively prevent the arsenic fixing agent from caking and agglomerating due to one-time addition of the arsenic fixing agent due to slow release of the arsenic fixing agent, so that the use efficiency of the arsenic fixing agent is effectively improved.

(4) The slow-release arsenic fixing agent for arsenic-polluted soil provided by the invention has the advantages of simple production process, no secondary pollution and the like, and is easy to realize industrial application.

Drawings

FIG. 1 is a flow chart of a preparation process of the slow-release arsenic fixing agent for arsenic-contaminated soil.

Detailed Description

The present disclosure will be described in further detail with reference to the drawings and specific examples, which are provided for illustrative purposes and for explaining the present disclosure, and should not be construed as limiting the scope of the present disclosure. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

The instruments, reagents, etc. used in the following examples are, unless otherwise indicated, available by conventional commercial means.

Example 1

(1) Putting chitosan into a container, and mixing the chitosan and the chitosan according to a liquid-solid ratio of 10 mL: adding 1g of glacial acetic acid solution with the pH value of 6, starting stirring, heating and keeping the temperature at 60 ℃, and adding vanillin accounting for 60 percent of the mass of the chitosan while stirring. Stirring at constant temperature for reaction for 0.5h, filtering when the reaction is finished, washing the filter residue with distilled water, transferring into a constant-temperature oven, and drying at 80 deg.C to constant weight to obtain vanillin modified chitosan.

(2) 60 parts of fly ash and 40 parts of kaolin are mixed and then roasted for 4 hours at 600 ℃, and then ground to 50 meshes, so as to prepare the high-activity adsorbing material.

(3) Drying the red mud at 95 ℃, and grinding the dried red mud to 200 meshes.

(4) Mixing 10 parts of high-activity adsorbing material, 3 parts of calcium sulfide powder and 87 parts of red mud powder, and then oscillating on a shaking table for 2 hours at the oscillation frequency of 300 rpm.

(5) And (4) adding 6 parts of vanillin modified chitosan into the fixing agent prepared in the step (4), stirring and heating to a molten state, continuously stirring for 1 hour, and cooling to prepare particles with the particle size of 3 mm.

Example 2

(1) Placing chitosan into a container, and mixing the chitosan and the chitosan according to a liquid-solid ratio of 20 mL: adding 1g glacial acetic acid solution with pH of 7, stirring, heating and maintaining the temperature at 80 deg.C, and adding vanillin 90% by mass of chitosan while stirring. Stirring at constant temperature for reaction for 2h, filtering when the reaction is finished, washing the filter residue with distilled water, transferring into a constant temperature oven, and drying at 60 ℃ to constant weight to obtain vanillin modified chitosan.

(2) 70 parts of fly ash and 30 parts of kaolin are mixed and then roasted for 1 hour at 800 ℃, and ground to 80 meshes to prepare the high-activity adsorbing material.

(3) Drying the red mud at 100 ℃, and grinding to 300 meshes.

(4) Mixing 5 parts of high activity adsorption material, 5 parts of calcium sulfide powder and 90 parts of red mud powder, and then oscillating on a shaking table for 1h, wherein the oscillation frequency is 400 rpm.

(5) And (4) adding 8 parts of vanillin modified chitosan into the fixing agent prepared in the step (4), stirring and heating to a molten state, continuously stirring for 0.5h, and cooling to prepare particles with the particle size of 4 mm.

Comparative example 1

(1) 60 parts of fly ash and 40 parts of kaolin are mixed and then roasted for 4 hours at 600 ℃, and then ground to 50 meshes, so as to prepare the high-activity adsorbing material.

(2) Drying the red mud at 95 ℃, and grinding the dried red mud to 200 meshes.

(3) Mixing 10 parts of high-activity adsorbing material, 3 parts of calcium sulfide powder and 87 parts of red mud powder, and then oscillating on a shaking table for 2 hours at the oscillation frequency of 300 rpm.

(4) And (4) adding 6 parts of unmodified chitosan into the fixing agent prepared in the step (3), stirring and heating to a molten state, continuing stirring for 1h, and cooling to prepare particles with the particle size of 3 mm.

Comparative example 2

(1) Putting chitosan into a container, and mixing the chitosan and the chitosan according to a liquid-solid ratio of 10 mL: adding 1g of glacial acetic acid solution with the pH value of 6, starting stirring, heating and keeping the temperature at 60 ℃, and adding vanillin accounting for 60 percent of the mass of the chitosan while stirring. Stirring at constant temperature for reaction for 0.5h, filtering when the reaction is finished, washing the filter residue with distilled water, transferring into a constant-temperature oven, and drying at 80 deg.C to constant weight to obtain vanillin modified chitosan.

(2) Drying the red mud at 95 ℃, and grinding the dried red mud to 200 meshes.

(3) 3.3 parts of calcium sulfide powder and 96.7 parts of red mud powder are mixed and then are vibrated on a table concentrator for 2 hours, and the vibration frequency is 300 rpm.

(4) And (4) adding 6 parts of vanillin modified chitosan into the fixing agent prepared in the step (3), stirring and heating to a molten state, continuously stirring for 1 hour, and cooling to prepare particles with the particle size of 3 mm.

Comparative example 3

(1) 60 parts of fly ash and 40 parts of kaolin are mixed and then roasted for 4 hours at 600 ℃, and then ground to 50 meshes, so as to prepare the high-activity adsorbing material.

(2) Drying the red mud at 95 ℃ and grinding the dried red mud to 200 meshes.

(3) Mixing 10 parts of high-activity adsorbing material, 3 parts of calcium sulfide powder and 87 parts of red mud powder, and then oscillating on a shaking table for 2 hours at the oscillation frequency of 300 rpm.

Examples 1-2 and comparative examples 1-3. As slow-release arsenic fixing agent 5 in total, arsenic fixing effect test:

the method comprises the steps of selecting soil of a treatment project of an arsenic-polluted site in Hunan province as a test material, leaching the polluted soil according to a horizontal oscillation method (HJ557-2009) of a solid waste leaching toxicity leaching method, and detecting the content of arsenic in a leaching solution. The detection proves that the toxicity of arsenic leaching in the polluted soil is 0.52402 mg/L.

(1) Example 1 arsenic fixing effect test of the prepared slow-release arsenic fixing agent:

and (2) putting soil to be tested into a reaction container, spraying a small amount of distilled water to keep the soil in a wet state, adding the slow-release arsenic fixing agent prepared in the example 1 according to 3% of the mass of the soil, uniformly stirring, maintaining, sampling every day for maintaining, and detecting the leaching toxicity of arsenic in the soil to be tested, wherein the period is 1 week.

(2) Example 2, comparative example 1, comparative example 2, and comparative example 3 the slow release arsenic fixing agent arsenic fixing effect test:

the slow release arsenic fixing agents prepared in example 2, comparative example 1, comparative example 2 and comparative example 3 were tested according to the experimental method of example 1.

(3) Experimental results and analysis:

TABLE 1 test of arsenic fixing effect of slow-release arsenic fixing agent

As can be seen from table 1, according to the comparison of example 1, comparative example 1 and comparative example 3, it is found that the arsenic fixing agent coating vanillin modified chitosan has improved action time, better slow release effect and better arsenic fixing effect, because the hydroxyl group on vanillin modified chitosan can form a stable chelate with arsenic while the vanillin modified chitosan has a slow release effect, the effect after modification is better, and the chitosan without vanillin modification does not contain phenolic hydroxyl group with chelating arsenic ion, and the effect of fixing arsenic is worse than that of vanillin modified chitosan. Comparative example 1 and comparative example 2 show that the introduction of the activated high adsorption material has a good effect of reducing the arsenic migration, because the activated adsorption material has a larger specific surface area, and can adsorb and wrap the fixed arsenic concentrate, thereby reducing the possibility of releasing the arsenic concentrate due to environmental damage.