In-situ passivator for passivating cadmium in tailings

Abstract

The invention relates to the field of tailing passivators, and particularly discloses an in-situ passivator for passivating cadmium in tailings, a preparation method comprises the following steps: S1, adding attapulgite into hydrochloric acid for soaking, and then washing and filtering to obtain acid-washed attapulgite; s2, adding the acid-washed attapulgite into a phosphate solution, then adjusting the pH value to 10-11, reacting at 150-200 DEG C, and then filtering to obtain phosphoric acid modified attapulgite; and S3, carrying out high-temperature drying on the phosphoric acid modified attapulgite at 300-400 DEG C, and then grinding until the particle size is less than 400 meshes. The passivator disclosed by the invention is simple in preparation method, convenient to use and easy to recover, can be desorbed and adsorbed as acid-washed attapulgite only through acid washing, and is green and pollution-free. Cadmium on the surfaces of the tailings can be efficiently complexed and adsorbed, the cadmium removal rate reaches 70% or above, cadmium passivation is achieved, and cadmium pollution caused by tailings accumulation to soil is avoided.

Description

Technical Field

[0001] The invention relates to the field of tailings passivators, in particular to an in-situ passivator for passivating cadmium in tailings. Background Art

[0002] Tailings refer to the part of the product of the sorting operation in the beneficiation process that has a low content of useful target components and cannot be used for production. The continuous development and utilization of mineral resources and the rapid development of the mining industry are also accompanied by the generation of a large amount of tailings. The large accumulation of tailings will affect the surrounding soil environment, resulting in a large amount of waste of land resources, and will also affect the ecological environment around the mining area, further threatening human production activities. Li et al. conducted a data collection study on 72 mining areas in 22 provinces and regions in my country and found that the contents of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn) and mercury (Hg) in the soil around the mining area and the tailings area were 6.5, 36.5, 0.4, 2.1, 2.1, 2.1, 4.7 and 7.6 times higher than the Chinese secondary quality environmental standards, among which Cd pollution was the most serious.

[0003] In order to effectively remove heavy metals from the soil, various remediation technologies have been developed, but these technologies consume a lot of manpower and material resources, and the remediation process occupies land resources and destroys soil structure. In-situ passivation remediation technology adds passivators to the soil to cause physical and chemical interactions between it and heavy metals, including precipitation, redox, complexation and surface adsorption. It is a technology that changes the form of heavy metals, reduces the mobility of heavy metals, and thus minimizes the potential utilization of heavy metals by plants, microorganisms and water. It has the outstanding advantages of cost-effectiveness and rapid implementation.

[0004] Treatment of contaminated areas usually includes solidification / stabilization, thermal analysis, soil leaching and vitrification. Among them, the passivation agent solidification method is based on the stabilization of heavy metals in tailings / soil or slag with chemical reagents that are harmless to the environment or have little impact. Chemical and biological measures are used to change the existence form of heavy metals through precipitation, chemical adsorption and ion exchange, organic complexation, oxidation-reduction and other effects, reduce the biological effectiveness and mobility of heavy metals, and reduce the environmental risks of heavy metals. However, most of the existing passivators are targeted at contaminated soil near tailings, and cannot directly prevent the occurrence of pollution. In addition, it is difficult to determine the amount to be used when the scope of pollution is unknown.

[0005] In the prior art, Chinese invention CN202210047342.3 discloses a long-acting tailings passivator that can be cured at room temperature, its preparation method and application, which can directly passivate pyrite particles, but the raw materials of the passivator are expensive, and the passivation principle is to form an oxide layer on the surface of the tailings, which is easily corroded by oxygen and water in the environment. Chinese invention CN202311138902.7 discloses a method for in-situ passivation and stabilization treatment of iron-containing tailings, but its passivator is mainly used for iron tailings, and no research has been conducted on the passivation of heavy metal cadmium. In summary, there is an urgent need for an in-situ passivator that can be directly applied to piled tailings to directly avoid the pollution of the surrounding environment by cadmium-containing tailings. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an in-situ passivating agent for passivating cadmium in tailings, so as to at least achieve low preparation cost, simple use method and good cadmium passivation effect.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] An in-situ passivating agent for passivating cadmium in tailings, the preparation method is as follows:

[0009] S1: soaking attapulgite in hydrochloric acid, then washing and filtering to obtain acid-washed attapulgite;

[0010] S2: adding the acid-washed attapulgite to a phosphate solution, adjusting the pH to 10 to 11, reacting at 150 to 200° C., and filtering to obtain phosphoric acid-modified attapulgite;

[0011] S3: drying the phosphoric acid-modified attapulgite at 300-400° C., and then grinding the attapulgite to a particle size of less than 400 meshes.

[0012] Furthermore, in step S1, the soaking time is 1 to 2 hours.

[0013] Furthermore, in step S1, the concentration of the hydrochloric acid is 36-38%.

[0014] Furthermore, in step S2, the particle size of the attapulgite is less than 200 mesh.

[0015] Furthermore, in step S2, the phosphate in the phosphate solution includes sodium pyrophosphate solution or disodium hydrogen phosphate solution.

[0016] Furthermore, in step S2, the amount of attapulgite added to each liter of the phosphate solution is 20 to 50 g.

[0017] Furthermore, in step S3, the high temperature drying time is 3-4 hours.

[0018] The method for using the in-situ passivating agent comprises the following steps:

[0019] The passivating agent is added into water and sodium carbonate to form a turbid liquid, the cadmium-containing tailings are added into the turbid liquid for shaking and stirring, and then the cadmium-containing tailings are taken out for cleaning.

[0020] Furthermore, the weight ratio of the passivating agent, water and sodium carbonate is 1:40-50:1-2.

[0021] Furthermore, the oscillating stirring time is 1 to 2 hours.

[0022] The principle of the present invention is: firstly, the impurity metal ions and carbonate impurities in attapulgite are washed out by acid modification, the adsorption potential of attapulgite is increased, the specific surface area is expanded, and then phosphoric acid modification is carried out under alkaline conditions, the phosphate ions are easily adsorbed by attapulgite, and the added phosphate is adsorbed on the active sites of attapulgite. The adsorbed water and crystal water in attapulgite are removed by thermal modification, the pore position of attapulgite is reduced, the phosphate is not easily eluted, and it is more closely combined with attapulgite. When the modified attapulgite contacts with cadmium-containing tailings, a complex reaction will occur under alkaline conditions to generate a complex, and the generated complex will also be adsorbed again by attapulgite, and will not cause pollution to the environment.

[0023] The beneficial effects of the present invention are:

[0024] 1. The passivating agent preparation method of the present invention is simple, convenient to use, and easy to recycle. It can be desorbed and recovered as pickled attapulgite only by pickling, which is green and pollution-free.

[0025] 2. The present invention can efficiently complex and adsorb cadmium on the surface of tailings, with a cadmium removal rate of more than 70%, thereby achieving cadmium passivation and avoiding cadmium pollution of the soil caused by tailings accumulation. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below, but the protection scope of the present invention is not limited to the following.

[0027] Example 1

[0028] The in-situ passivation agent is prepared as follows:

[0029] 1. Ball mill the attapulgite (purchased from Changzhou Dingbang Mineral Products Co., Ltd.) and pass it through a 200-mesh sieve.

[0030] 2. Take 2000.4 g of sieved attapulgite and put it into a beaker. Pour 3 mol / L hydrochloric acid solution into it until the attapulgite is submerged. After 2 hours, wash and filter with clean water to obtain 1890.5 g of acid-washed attapulgite.

[0031] 3. Add 1000 g of acid-washed attapulgite into a sodium pyrophosphate solution (20 wt%), add sodium hydroxide to adjust the pH to 11, then heat to 150° C., react for 30 min, filter and wash to obtain phosphoric acid-modified attapulgite.

[0032] 4. Transfer the phosphoric acid-modified attapulgite to a muffle furnace for calcination, set the temperature to 400°C, and calcine for 3 hours.

[0033] 5. Take the modified attapulgite out of the muffle furnace, grind it finely to prevent the attapulgite from sticking, and pass it through a 400-mesh sieve to obtain the passivating agent.

[0034] Example 2

[0035] The in-situ passivation agent is prepared as follows:

[0036] 1. Ball mill the attapulgite (purchased from Changzhou Dingbang Mineral Products Co., Ltd.) and pass it through a 200-mesh sieve.

[0037] 2. Take 2001.2 g of sieved attapulgite and put it into a beaker. Pour 3 mol / L hydrochloric acid solution into it until the attapulgite is submerged. After 2 hours, wash and filter with clean water to obtain 1783.6 g of acid-washed attapulgite.

[0038] 3. Add 1000 g of acid-washed attapulgite into a sodium pyrophosphate solution (20 wt%), add sodium hydroxide to adjust the pH to 11, then heat to 180° C., react for 30 min, filter and wash to obtain phosphoric acid-modified attapulgite.

[0039] 4. Transfer the phosphoric acid-modified attapulgite to a muffle furnace for calcination, set the temperature to 350°C, and calcine for 4 hours.

[0040] 5. Take the modified attapulgite out of the muffle furnace, grind it finely to prevent the attapulgite from sticking, and pass it through a 400-mesh sieve to obtain the passivating agent.

[0041] Comparative Example 1

[0042] A passivating agent was prepared in the same manner as in Example 1, except that no acid modification was performed:

[0043] 1. Ball mill the attapulgite (purchased from Changzhou Dingbang Mineral Products Co., Ltd.) and pass it through a 200-mesh sieve.

[0044] 2. Take 975.8 g of the sieved attapulgite and put it into a beaker, add it into a sodium pyrophosphate solution (20 wt%), add sodium hydroxide to adjust the pH to 11, then heat to 150° C., react for 30 minutes, filter and wash to obtain phosphoric acid-modified attapulgite.

[0045] 3. Transfer the phosphoric acid-modified attapulgite to a muffle furnace for calcination, set the temperature to 400°C, and calcine for 3 hours.

[0046] 4. Take the modified attapulgite out of the muffle furnace, grind it finely to prevent the attapulgite from sticking, and pass it through a 400-mesh sieve to obtain the passivating agent.

[0047] Comparative Example 2

[0048] A passivating agent was prepared in the same manner as in Example 1, except that no high temperature modification was performed:

[0049] 1. Ball mill the attapulgite (purchased from Changzhou Dingbang Mineral Products Co., Ltd.) and pass it through a 200-mesh sieve.

[0050] 2. Take 1971.8 g of sieved attapulgite and put it into a beaker. Pour 3 mol / L hydrochloric acid solution into it until the attapulgite is submerged. After 2 hours, wash and filter with clean water to obtain 1756.3 g of acid-washed attapulgite.

[0051] 3. Add 1000 g of acid-washed attapulgite into a sodium pyrophosphate solution (20 wt%), add sodium hydroxide to adjust the pH to 11, then heat to 150° C., react for 30 min, filter and wash to obtain phosphoric acid-modified attapulgite.

[0052] 4. Transfer the phosphoric acid-modified attapulgite to a muffle furnace for calcination, set the temperature to 400°C, and calcine for 3 hours.

[0053] 5. Take the modified attapulgite out of the muffle furnace, grind it finely to prevent the attapulgite from sticking, and pass it through a 400-mesh sieve to obtain the passivating agent.

[0054] Experimental example

[0055] The passivating agents of Example 1-2 and Comparative Example 1-2 were used to verify the adsorption effect of cadmium, and the method was as follows:

[0056] The passivation agent, water and sodium carbonate were mixed in a weight ratio of 1:20:2, poured into a constant temperature oscillator, and then added with Anhui Tongling copper tailings particles. The mixture was oscillated at a constant temperature of 25°C for 2 hours. The cadmium content in the water was detected, and a blank group without the addition of the passivation agent was set as a blank control. The experimental results are as follows:

[0057] Experimental Group Cadmium content (mg / kg) Example 1 0.58 Example 2 0.56 Comparative Example 1 0.82 Comparative Example 2 0.74 blank 1.24

[0058] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. An in-situ passivating agent for passivating cadmium in tailings, characterized in that: The preparation method is as follows: S1: soaking attapulgite in hydrochloric acid, then washing and filtering to obtain acid-washed attapulgite; S2: adding the acid-washed attapulgite to a phosphate solution, adjusting the pH to 10 to 11, reacting at 150 to 200° C., and filtering to obtain phosphoric acid-modified attapulgite; S3: drying the phosphoric acid-modified attapulgite at 300-400° C., and then grinding the attapulgite to a particle size of less than 400 meshes.

2. The in-situ passivating agent according to claim 1, characterized in that: In step S1, the soaking time is 1 to 2 hours.

3. The in-situ passivating agent according to claim 1, characterized in that: In step S1, the concentration of the hydrochloric acid is 36-38%.

4. The in-situ passivating agent according to claim 1, characterized in that: In step S2, the particle size of the attapulgite is less than 200 mesh.

5. The in-situ passivating agent according to claim 1, characterized in that: In step S2, the calcium salt of the phosphate solution includes a sodium pyrophosphate solution.

6. The in-situ passivating agent according to claim 5, characterized in that: In step S2, the amount of attapulgite added to each liter of the phosphate solution is 40 to 50 g.

7. The in-situ passivating agent according to claim 1, characterized in that: In step S3, the high temperature drying time is 3-4 hours.

8. The method for using the in-situ passivating agent according to any one of claims 1 to 7, characterized in that: The steps include: The passivating agent is added into water and sodium carbonate to form a suspension, the cadmium-containing tailings are added into the suspension, shaken and stirred, and then the cadmium-containing tailings are taken out and washed.

9. The method of use according to claim 8, characterized in that: The weight ratio of the passivating agent, water and sodium carbonate is 1:20-50:1-2.

10. The method of use according to claim 8, characterized in that: The shaking and stirring time is 1 to 2 hours.