CN111117641A

CN111117641A - Heavy metal passivator for water and soil remediation

Info

Publication number: CN111117641A
Application number: CN201911353495.5A
Authority: CN
Inventors: 马龙; 涂丛慧; 朱娜; 胥国勇; 应昌权; 张奕轩
Original assignee: Cross-Strait Tsinghua Research Institute (xiamen); Xiamen Instant Environmental Materials Technology Co Ltd
Current assignee: Cross-Strait Tsinghua Research Institute (xiamen); Xiamen Instant Environmental Materials Technology Co Ltd
Priority date: 2019-12-25
Filing date: 2019-12-25
Publication date: 2020-05-08

Abstract

The invention discloses an in-situ passivator for heavy metal polluted water and soil, and relates to the technical field of heavy metal polluted water and soil treatment. The heavy metal passivator is prepared by performing ultrasonic sulfhydrylation modification on sodium bentonite after nanocrystallization, wherein the sulfhydrylation modifier is a mixture of cysteine hydrochloride and trimercapto-s-triazine trisodium salt. The heavy metal passivator can effectively adsorb monovalent and divalent heavy metal ions such as Hg, Cu, Cd, Ag, Pb, Ni and the like, can be used for repairing heavy metal polluted water and soil, can remarkably reduce the bioactivity of heavy metals in the water and the soil, and improves the water quality and the soil property while passivating the heavy metals in situ.

Description

Heavy metal passivator for water and soil remediation

Technical Field

The invention belongs to the technical field of treatment of heavy metal pollution of water and soil, and particularly relates to a heavy metal passivator for water and soil.

Background

Heavy metals enter water and soil in the forms of artificial pollution sources such as mining, metal smelting, metal processing and chemical production wastewater, combustion of fossil fuels, application of pesticides, fertilizers, household garbage and the like, and natural sources such as geological erosion, weathering and the like, and the heavy metals have the characteristics of high toxicity, difficulty in being metabolized in the environment, easiness in being biologically enriched, biological amplification effect and the like, not only pollute the environment, but also seriously threaten the survival of human beings and organisms.

The problem of heavy metal pollution of water bodies in China is quite prominent, and the pollution rate of sediments in rivers, lakes and reservoirs is as high as 80.1%. In 2003, the pollution degree of heavy metal exceeding cross sections of river basin slices in ten large river basins such as yellow river, Huaihe river, Songhua river, Liaohe river and the like is in class V. In 2004, the contents of total copper, total lead and total cadmium in the bottom mud of the Taihu lake are in a mild pollution level. Cd in the surface sediments of the Huangpu river is 2 times higher than the background value, Pb is 1 time higher than the background value, and Hg content is obviously increased; pb in Suzhou river exceeds the standard, Cd exceeds the standard by 75%, and Hg exceeds the standard by 62.5%. In urban rivers, 35.11% of river reach shows that total mercury exceeds III-class water body standards of surface water, 18.46% of river reach total cadmium exceeds III-class water body standards, and 25% of river reach shows that standard exceeding samples of total lead appear. The total amount of heavy metal pollutants carried into the sea by rivers such as Yangtze river, Zhujiang river, yellow river and the like is about 3.4 ten thousand tons, and the pollution to the ocean water body is huge. The standard exceeding rate of Pb in seawater samples in the coastal sea area of China reaches 62.9 percent, and the maximum value exceeds 49.0 times of the standard of first-class seawater; the standard exceeding rate of Cu is 25.9%, and the content of Hg and Cd also exceeds the standard.

The situation of heavy metal pollution of soil in China is also severe, and according to statistics, the area of the cultivated land polluted by heavy metal in China is about 2.0 multiplied by 107hm2, which accounts for about 20% of the total area of the cultivated land, and medium-light pollution is mainly used. After heavy metals enter farmland soil, the heavy metals have negative effects on the number of soil microorganisms, population structure and soil enzyme activity, so that the soil fertility is reduced, the normal metabolism process of crops is interfered, the yield and quality of the crops are reduced, and finally the heavy metals are accumulated in a human body through a food chain to cause harm to the health of the human body.

At present, people have relatively deep research on the problem of heavy metal pollution of water bodies, and various methods are adopted to treat and repair heavy metal wastewater and polluted water bodies. The treatment of the heavy metal pollution of the water body comprises two aspects of exogenous control and endogenous control. The external source control is mainly used for treating waste water and waste residues containing heavy metals discharged in mining, electroplating, metal smelting, chemical production and the like, and limiting the discharge amount of the waste water and the waste residues; endogenous control is the remediation of contaminated water bodies. Common methods include a coagulating sedimentation method, an adsorption method, a membrane separation method, a bioremediation method and the like, wherein although the lime neutralization sedimentation method has low price, the amount of sediment is large, the hardness of effluent is high, the reaction speed is slow, and the piled sediment causes secondary pollution; the ion exchange and membrane separation technology has high investment; the bioremediation technology has the advantages of less types and quantity of microorganisms with special degradation capability in the environment, long treatment period and high investment.

Common heavy metal contaminated soil remediation measures include chemical passivation, a thermal desorption method, soil leaching, bioremediation and the like. Wherein, the plant restoration method has long time, high cost and great difficulty in seedling breeding operation; the chemical leaching method needs to add a surfactant, a pickling agent and the like, so that the cost is high and new pollution is caused; chemical passivation is one of soil heavy metal pollution treatment methods commonly used at home and abroad, has short treatment time, economy, low price and wide application range, but can not remove heavy metals from soil, but can exist in the soil in a more stable form.

The main types of the commonly used passivators are inorganic, organic, microbial, novel composite materials, chelating agents and the like. The inorganic passivator mainly comprises clay minerals (sepiolite, zeolite, bentonite, kaolin and the like), industrial byproducts (fly ash, lime, red mud, silicon powder, gypsum and the like), phosphates and metal oxides (calcium superphosphate, ground phosphate rock, calcium magnesium phosphate fertilizer, hydroxyapatite, phosphate, magnesium oxide and the like) and other industrial and agricultural wastes (peat, slag, cement and the like); the organic passivator mainly comprises animal wastes, straws, biochar, black carbon, municipal domestic sludge and the like; the microbial passivator mainly comprises mycorrhiza, reducing bacteria and the like; the novel composite material mainly comprises a modified mineral material, an inorganic organic substance composite matching material, a nano material and the like; in addition, there are some chelating agents such as EDTA, DTPA, NTA, etc.

The heavy metal passivator is generally added in proportion when soil is ploughed, pH is a key factor influencing passivation, and passivation is related to the specific surface area, adsorption performance and ion exchange capacity of the passivator, biological reaction possibly caused in the passivation process, soil microbial environment change and the like. At present, more passivators such as bentonite, sepiolite, lime, red mud, phosphate and the like are applied in engineering, certain passivation effect is achieved on heavy metals, but the passivation effect is still less than 50%, the passivators have high selectivity and great change on physical and chemical properties of soil, dissolution of aluminum, phosphorus and the like and re-dissolution and release of heavy metals exist, secondary pollution is easily caused, and the addition amount needs to be carefully controlled.

Chinese patent (patent No. 200510002116.X) adopts sodium bentonite, sepiolite, attapulgite, fly ash and microbial roots to be mixed according to proportion to prepare the in-situ remediation agent for the heavy metal contaminated soil; the Chinese patent application No. 200910232564.7 has a certain passivation effect on Cu, Zn and Cd in the soil by adding attapulgite with the proportion of less than or equal to 8% in the heavy metal contaminated soil; the Chinese patent application No. 201110056525.3 discloses that the weight ratio of submicron or nanometer iron, fly ash, magnesium-containing preparation and bentonite is 5-25: 40-50: 1-10: uniformly mixing the materials in a weight ratio of 15-50 to obtain a heavy metal contaminated soil remediation agent; chinese patent application No. 201310536543.0 uses aluminum salt modified bentonite as a heavy metal ion stabilizer. Chinese patent No. 201310135109.1, a mercapto-iron-based modified clay is obtained by stirring modified clay at room temperature with a mercapto compound and iron glycolate, and is mainly used for removing Cr in soil; the Chinese patent application No. 201310060021.8 adopts a polyglutamic acid and thiocyanuric acid composition for solidifying heavy metals in water and soil; the Chinese patent application No. 201410243192.9 extracts the humins from the peat soil and sulfhydrylates the humins to obtain a sulfhydryl humins passivator, which can improve the passivation rate of Cd in the polluted soil; the Chinese patent application No. 201110302519.1 adopts inorganic minerals such as bentonite, etc., adds surfactant for modification at room temperature, then adds organic complexing agent containing sulfydryl or amido for stirring to obtain heavy metal adsorbent, which can be used for in-situ remediation of water and soil, the method is conventional for stirring modification at room temperature, and the modification degree is lower; the used sulfhydryl modifier is a toxic medicament, and is likely to be dissolved out to cause secondary pollution when put into use.

Although certain effect is achieved on the passivation effect of heavy metals in water and soil at present, the use of a large amount of passivators has the potential risks of destroying water quality, soil structures, secondarily releasing heavy metals, polluting surface water and underground water and the like, so that the development of an environment-friendly, cheap and easily-obtained heavy metal passivator with strong stable adsorption capacity is urgently needed, the heavy metals can be passivated with low dosage, and the secondary release of the heavy metals is avoided, so that the environment is improved.

From the inorganic chemistry, it is known that sulfur has high affinity for divalent cations of heavy metals Hg, Cd, Pb, Cu, Zn, Ni, etc., and many scholars introduce sulfur-containing organic functional groups into cotton fibers, activated carbon, distiller's grains, cotton, clinoptilolite, etc. to enrich and separate heavy metal elements in water. However, different types of biomass materials have different chemical compositions and have different adsorption capacities. The bentonite in China has rich resources, is cheap and easy to obtain, has larger specific surface area and has good adsorption performance on heavy metals; and the bentonite has ion exchange property and more hydroxyl on the surface, and can react with a sulfhydrylation reagent to form the sulfhydrylation modified bentonite. The bentonite product after sulfydryl modification has better adsorption effect on heavy metals, and the heavy metals can be converted into a residue state after adsorption, thereby being beneficial to improving the passivation effect of the heavy metals.

Disclosure of Invention

The invention aims to develop a heavy metal passivator for water and soil pollution, which has strong adsorption capacity, small dosage and stability after heavy metal adsorption; the product is environment-friendly and does not cause secondary pollution; the method is cheap and easy to obtain, is suitable for large-scale popularization, and can effectively repair the heavy metal polluted water body and soil.

The invention realizes the aim through the following technical scheme:

a passivator for heavy metal polluted water and soil, which is characterized in that,

1. a passivator for heavy metal polluted water and soil comprises bentonite and a sulfhydrylation modifier, wherein the total content of the sulfhydrylation modifier is 1-1.5 times of the cation exchange capacity of the used bentonite.

2. The sulfhydrylation modifier is formed by mixing cysteine hydrochloride and trimercapto-s-triazine trisodium salt according to a molar ratio of 1: 1-1: 15.

3. The bentonite is sodium bentonite which is subjected to nanocrystallization treatment.

Compared with the existing heavy metal passivator for repairing water and soil, the invention has the following advantages:

1. the heavy metal passivator for water and soil remediation disclosed by the invention is used for nanocrystallizing the raw material sodium bentonite, so that sulfhydrylation modification is facilitated, and meanwhile, the prepared heavy metal passivator product is large in specific surface area and strong in adsorption capacity;

2. according to the heavy metal passivator for repairing water and soil, the adopted sulfhydrylation reagent is a mixture of cysteine hydrochloride and trimercapto-s-triazine trisodium salt, and the two modifiers are safe, non-toxic and environment-friendly; cysteine can be used as a heavy metal antidote, the trimercapto-s-triazine trisodium salt solution is a heavy metal collecting agent, the cysteine hydrochloride aqueous solution is acidic, the trimercapto-s-triazine trisodium salt aqueous solution is alkaline, the two are mixed according to a proportion, the modified bentonite does not change the physical and chemical properties such as the pH value of water and soil when being put into the water and the soil for use, and the modified bentonite has better adsorption performance and wider application range.

3. The heavy metal passivator for water and soil remediation is used for carrying out sulfhydrylation modification under the ultrasonic condition, and carrying out sulfhydrylation modification by utilizing a transient high-energy environment generated by an ultrasonic cavitation effect, and has the advantages of high modification speed, good effect, normal temperature and pressure reaction, low energy consumption, and simple process flow and reaction equipment.

4. The heavy metal passivator for repairing water and soil is particularly suitable for water and soil polluted by monovalent and divalent heavy metal ions such as Hg, Cu, Cd, Ag, Pb, Ni and the like, the heavy metal passivator can reach more than 98%, and the passivated soil can reach the national standard after a toxicity leaching test according to hazardous waste identification standard leaching toxicity identification (GB 5085.3-2007).

Detailed Description

Example 1:

the preparation method of the heavy metal passivator for repairing water and soil comprises the following steps:

(1) taking the sodium bentonite produced by holy, wherein the purity of montmorillonite is more than 90 percent, and CEC (cation exchange capacity) is 100-120 mmol/100g of soil, and carrying out nanocrystallization through airflow crushing;

(2) cysteine hydrochloride and TMT-15 (15% solution of trimercapto s-triazine trisodium salt) are mixed according to the effective component molar ratio of 1:1 to be used as a sulfydryl modifier, and the total dosage of the modifier is 100mmol/100 g;

(3) and (3) taking 20g of nano sodium-based soil, mixing the nano sodium-based soil into slurry according to the liquid-solid ratio of 10:1, adding a mixed solution of a sulfhydryl modifier, fully stirring the mixture, placing the mixture into an ultrasonic cell crusher, carrying out ultrasonic treatment for 0.5h, filtering, washing and drying the mixture to obtain the heavy metal passivator.

Example 2:

(2) cysteine hydrochloride and TMT-15 (15% solution of trimercapto s-triazine trisodium salt) are mixed according to the effective component molar ratio of 1:1 to be used as a sulfydryl modifier, and the total dosage of the modifier is 150mmol/100 g;

Example 3:

(1) taking the sodium bentonite produced by holy, wherein the purity of montmorillonite is more than 90%, and CEC (cation exchange capacity) is 100-120 mmol/100g of soil;

(2) cysteine hydrochloride and TMT-15 (15% solution of trimercapto-s-triazine trisodium salt) are mixed according to the effective component molar ratio of 1:8 to be used as a sulfydryl modifier, and the total dosage of the modifier is 110mmol/100 g;

(3) and (2) taking 20g of nano sodium-based soil, mixing the nano sodium-based soil into slurry according to the liquid-solid ratio of 10:1, adding a sulfydryl modifier, fully and uniformly stirring the mixture, putting the mixture into an ultrasonic cell crusher, carrying out ultrasonic treatment for 1 hour, filtering, washing and drying the mixture to obtain the heavy metal passivator.

Example 4:

(1) taking sodium bentonite produced in Xinjiang, wherein the purity of montmorillonite is over 90 percent, and CEC (cation exchange capacity) is 100-120 mmol/100g of soil, and carrying out nanocrystallization through airflow crushing;

(2) cysteine hydrochloride and TMT-15 (15% solution of trimercapto-s-triazine trisodium salt) are mixed according to the effective component molar ratio of 1:8 to be used as a sulfydryl modifier, and the total dosage of the modifier is 160mmol/100 g;

Example 5:

(2) cysteine hydrochloride and TMT-15 (15% solution of trimercapto-s-triazine trisodium salt) are mixed according to the effective component molar ratio of 1:15 to be used as a sulfydryl modifier, and the total dosage of the modifier is 100mmol/100 g;

Example 6:

(2) cysteine hydrochloride and TMT-15 (15% solution of trimercapto-s-triazine trisodium salt) are mixed according to the molar ratio of the effective components of 1:15 to be used as a sulfydryl modifier, and the total dosage of the modifier is 150mmol/100 g;

(3) and (2) taking 20g of nano sodium-based soil, mixing the nano sodium-based soil into slurry according to the liquid-solid ratio of 10:1, adding a sulfydryl modifier, fully and uniformly stirring the mixture, putting the mixture into an ultrasonic cell crusher, carrying out ultrasonic treatment for 2 hours, filtering, washing and drying the mixture to obtain the heavy metal passivator.

Claims

1. The passivator for the heavy metal polluted water and soil is characterized by comprising bentonite and a sulfhydrylation modifier, wherein the total content of the sulfhydrylation modifier is 1-1.5 times of the cation exchange capacity of the used bentonite.

2. The passivator for heavy metal polluted water and soil according to claim 1, wherein the sulfhydrylation modifier is a mixture of cysteine hydrochloride and trimercapto-s-triazine trisodium salt according to a molar ratio of 1: 1-1: 15.

3. The passivator for heavy metal polluted water and soil according to claim 1, wherein the total content of the thiolation modifier is 1 times of the cation exchange capacity of the bentonite used.

4. The passivator for heavy metal polluted water and soil according to claim 1, wherein the total content of thiolation modifier is 1.5 times of cation exchange capacity of bentonite used.

5. The passivator for heavy metal polluted water and soil according to claim 2, wherein the thiolation modifier is cysteine hydrochloride and trimercaptos-triazine trisodium salt in a molar ratio of 1: 1.

6. The passivator for heavy metal polluted water and soil according to claim 2, wherein the thiolation modifier is cysteine hydrochloride and trimercaptos-triazine trisodium salt in a molar ratio of 1: 8.

7. The passivator for heavy metal polluted water and soil according to claim 2, wherein the thiolation modifier is cysteine hydrochloride and trimercaptos-triazine trisodium salt in a molar ratio of 1: 15.

8. The passivator for heavy metal polluted water and soil according to any one of the preceding claims, wherein the bentonite is sodium bentonite.

9. The passivator for heavy metal polluted water and soil according to claim 8, wherein the sodium bentonite is subjected to nanocrystallization.