A method for remediation of antimony-arsenic contaminated soil and a preparation method of silicon-calcium-based material

Abstract

The application provides a method for repairing antimony-arsenic contaminated soil and a preparation method of a silicon-calcium-based material, and comprises the following steps: step 1: placing the silicon-calcium-based material into SRB bacterial solution for biofilm formation, so that the SRB bacteria are loaded on the silicon-calcium-based material to obtain a silicon-calcium-based biomaterial; and step 2: mixing the obtained silicon-calcium-based biomaterial with antimony-arsenic contaminated soil to repair the antimony-arsenic contaminated soil. The application uses SRB bacteria and a prepared silicon-calcium-based material to jointly solidify antimony and arsenic in the soil, removes the heavy metals in the soil, effectively maintains the amount of microorganisms to improve the solidification efficiency of the heavy metals in the soil, that is, the prepared silicon-calcium-based material carries a large amount of SRB bacteria, the large amount of SRB bacteria produces more hydrogen sulfide, and the hydrogen sulfide reacts with more heavy metals in the antimony-arsenic contaminated soil to form insoluble metal sulfide precipitates, so that the solidification efficiency of antimony and arsenic is improved.

Description

Technical Field

[0001] This invention relates to the field of heavy metal soil pollution remediation technology, and in particular to a method for remediating antimony and arsenic contaminated soil and a method for preparing silicon-calcium based materials. Background Technology

[0002] Soil is the core of land resources, a complex and open material system situated between the biological and abiotic worlds. Heavy metal pollution in soil has become a regional environmental problem. Heavy metal pollution from mining is a major environmental issue in soil pollution today, attracting much attention from scholars due to its wide range, long duration, hidden nature, and inability to be biodegraded.

[0003] There are various existing soil heavy metal remediation technologies in China, mainly including physical remediation, chemical remediation, and bioremediation. Traditional chemical remediation—lime precipitation—generates large amounts of metal-contaminated sludge and is costly. A promising alternative is microbial soil remediation, using sulfate-reducing bacteria (SRB) to solidify (precipitate) antimony and arsenic in antimony-contaminated soil from antimony mining areas, thus achieving soil remediation.

[0004] Existing studies have shown that SRB bacteria remediation technology is effective in treating antimony and arsenic in contaminated soil in antimony mining areas, but there are still technical problems such as low antimony and arsenic solidification efficiency and unstable treatment effect on arsenic. Summary of the Invention

[0005] To address the above problems, in a first aspect, the present invention provides a method for remediating antimony and arsenic contaminated soil, comprising the following steps:

[0006] Step 1: Place the silicon-calcium based material into the SRB bacterial solution for biofilm formation, so that the SRB bacteria are loaded onto the silicon-calcium based material to obtain silicon-calcium based biomineralized material;

[0007] Step 2: Mix the obtained silicon-calcium-based biomineralized material with antimony-arsenic contaminated soil to remediate the antimony-arsenic contaminated soil.

[0008] Preferably, the silicon-calcium based material is spherical.

[0009] Preferably, after mixing the obtained silicon-calcium-based biomineralized material with antimony-arsenic contaminated soil, the method further includes:

[0010] SRB bacterial solution was sprayed onto the antimony and arsenic contaminated soil to remediate the soil.

[0011] Preferably, the film attachment time is 24 h to 48 h.

[0012] In a second aspect, the present invention provides a method for preparing the silicon-calcium based material of the first aspect described above, comprising the following steps:

[0013] Step 1: Mix fly ash and bentonite and then ball mill them to obtain a mixture;

[0014] Step 2: The mixture is subjected to molding treatment to obtain a silicon-calcium based material.

[0015] Preferably, the silicon-calcium based material is spherical.

[0016] Preferably, the molding process of the mixture further includes:

[0017] The mixture is subjected to a molding process, during which Fe is sprayed. 3+ The solution yielded a solution containing Fe. 3+ A silicon-calcium based material; wherein, the Fe 3+ The concentration of the solution is 2 g / L to 10 g / L.

[0018] Preferably, after step 2, the method further includes:

[0019] The silicon-calcium based material is calcined to obtain the strengthened silicon-calcium based material; wherein the calcination time is 1 h to 2 h and the calcination temperature is 300 ℃ to 500 ℃.

[0020] Preferably, the mass ratio of fly ash to bentonite is 100:10 to 100:1.

[0021] Preferably, the particle size of the mixture is 200 mesh to 500 mesh.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] This invention provides a method for remediating antimony and arsenic contaminated soil and a method for preparing a silicon-calcium-based material, comprising the following steps: Step 1: Placing the silicon-calcium-based material into an SRB bacterial solution for biofilm formation, so that the SRB bacteria are loaded onto the silicon-calcium-based material to obtain a silicon-calcium-based biomineralization material; Step 2: Mixing the obtained silicon-calcium-based biomineralization material with antimony and arsenic contaminated soil to remediate the antimony and arsenic contaminated soil. This invention uses SRB bacteria and a prepared silicon-calcium-based material to jointly solidify antimony and arsenic in the soil. While removing heavy metals from the soil, it can effectively maintain the microbial biomass to improve the solidification efficiency of heavy metals in the soil. That is, the prepared silicon-calcium-based material can carry a large number of SRB bacteria. A large number of SRB bacteria produce more hydrogen sulfide, and then more hydrogen sulfide reacts with more heavy metals in the antimony and arsenic contaminated soil to form insoluble metal sulfide precipitates, thereby improving the solidification efficiency of antimony and arsenic.

[0024] This invention employs SRB bacteria and a silicon-calcium-based material to co-immobilize antimony and arsenic, thereby addressing the problems of low immobilization efficiency and unstable arsenic treatment effects when treating contaminated soil from antimony mining areas. Firstly, a silicon-calcium-based material with adsorption properties and a high specific surface area is placed in the SRB bacterial solution. This material effectively maintains the microbial biomass and can accommodate a larger amount of SRB bacteria. Since a higher SRB bacteria count leads to a greater immobilization effect on heavy metals in antimony and arsenic-contaminated soil, the resulting silicon-calcium-based biomineralization material is mixed with the antimony and arsenic-contaminated soil. The surface of the biomineralization material maintains a large number of SRB bacteria, which can produce more hydrogen sulfide. This hydrogen sulfide combines with the heavy metals in the antimony and arsenic-contaminated soil to form insoluble metal sulfide precipitates, thus effectively immobilizing the antimony and arsenic contaminants. The method effectively solidifies and removes antimony and arsenic from the soil, improving the solidification efficiency of antimony and arsenic contaminated soil remediation. Furthermore, the prepared silicon-calcium-based material, with its high specific surface area and adsorption efficiency, effectively maintains microbial biomass, enabling it to support more SRB bacteria and thus increasing the efficiency of heavy metal treatment in the soil. The prepared silicon-calcium-based material contains silicon and calcium, resulting in a high affinity for arsenic. Consequently, the silicon-calcium-based material itself also possesses a certain removal capacity for arsenic in contaminated soil, making the arsenic treatment effect more stable and long-lasting. In addition, the method provided by this invention is environmentally friendly, does not generate secondary pollution, has low treatment costs, utilizes waste to treat waste, can treat multiple types of heavy metals, and is highly practical. Attached Figure Description

[0025] Figure 1 A flowchart of a method for remediating antimony and arsenic contaminated soil provided by the present invention;

[0026] Figure 2 A physical image of a silicon-calcium based material provided by this invention;

[0027] Figure 3 (a) XRD pattern, (b) SEM image, and (c) EDS image of fly ash;

[0028] Figure 4 This is a comparison chart showing the removal efficiency of antimony and arsenic in antimony- and arsenic-contaminated soil from an antimony mining area, as shown in Example 1.

[0029] Figure 5 This is a comparison diagram of the solidification effect of antimony and arsenic in antimony-arsenic contaminated soil in the antimony mining area in Example 2;

[0030] Figure 6 This is a comparison diagram of the solidification effect of antimony and arsenic in antimony-arsenic contaminated soil in the antimony mining area in Example 3;

[0031] Figure 7 This is a comparison chart showing the solidification effect of silicon-calcium based biomineralization microspheres on antimony and arsenic contaminated soil in antimony mining areas after 20 days, as shown in Example 4. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the examples, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0033] Fly ash is a fine ash collected from the flue gas after coal combustion and is a major solid waste discharged from coal-fired power plants. With the development of the power industry, the amount of fly ash emitted by coal-fired power plants has been increasing year by year, becoming one of the largest industrial wastes in my country. Large amounts of fly ash, if left untreated, will generate dust, thus polluting the atmosphere; if discharged into waterways, it will cause river siltation, and the toxic chemicals in it will also harm human health and other organisms.

[0034] Bioremediation refers to the process of restoring the ecosystem of abandoned mining areas by fully utilizing the characteristics of plants and microorganisms; it is a composite reclamation method. Microbial solidification and stabilization technology utilizes mixed microorganisms for remediation, forming a microbial mineralization process, lowering the environmental potential, raising the pH value, and solidifying heavy metals in situ, transforming a vicious cycle into a virtuous one. It is low-cost, has good remediation effects, and causes minimal damage to the environment and soil structure, thus possessing greater development potential and application prospects. Microbial mineralization refers to the process by which microorganisms transform ionic heavy metals into solid minerals, precipitating heavy metal ions and reducing their bioavailability. Some microbial metabolic products (such as sulfide ions) react with metal ions to form precipitation reactions, converting toxic and harmful metal elements into non-toxic or low-toxic metal precipitates.

[0035] Therefore, the treatment of antimony and arsenic in contaminated soil from antimony mining areas is usually costly due to the variable valence states and poor stability of antimony and arsenic. A cost-effective method is biological induction to precipitate metal sulfides. This method is based on sulfate-reducing bacteria (SRB bacteria) using sulfate as the terminal electron acceptor during organic matter metabolism to produce sulfides. These sulfides can then remove the metal by forming insoluble metal sulfide precipitates. Microorganisms play a crucial driving role in the geochemical behavior of antimony (Sb), and the remediation technology for antimony-contaminated soil has great potential. Antimony and arsenic belong to the same main group and share similar properties. Arsenic (As(V)) typically exists as H₂AsO₄. - and HAsO4 2- Arsenic exists in the form of sulfur, which can be reduced to arsenic sulfides (realgar AsS and orpiment As2S3) under anaerobic conditions, or soluble arsenic sulfides can be generated when the arsenic concentration reaches equilibrium, thereby promoting or reducing the migration of arsenic and thus removing heavy metals from polluted soil.

[0036] Existing research indicates that the above methods are effective in treating antimony and arsenic in soil, but they still suffer from low antimony and arsenic solidification efficiency (low removal rate) and unstable arsenic treatment (lack of long-term effectiveness). The main reason for the unstable arsenic treatment effect and low removal rate is that As₂S₃ is more soluble than Sb₂S₃, making As₂S₃ formation more difficult. Furthermore, the applicant also found that adjusting the amount of SRB bacterial solution sprayed into the antimony and arsenic contaminated soil (appropriately increasing it) did not solve the problems of low antimony and arsenic solidification efficiency and unstable arsenic treatment.

[0037] In view of this, the present invention provides a method for remediating antimony and arsenic contaminated soil. A silicon-calcium based material obtained from fly ash, a solid waste, is placed in an SRB bacterial solution, allowing the SRB bacteria to be loaded onto the silicon-calcium based material. This allows the silicon-calcium based material to support a greater number of SRB bacteria, resulting in a silicon-calcium based biomineralization material. When this silicon-calcium based biomineralization material is mixed with antimony and arsenic contaminated soil, it can improve the antimony and arsenic solidification efficiency, and enhance the long-term effectiveness and removal rate of antimony and arsenic contaminated soil remediation. Firstly, referring to… Figure 1 , Figure 1 A flowchart of a method for remediating antimony and arsenic contaminated soil provided by the present invention includes the following steps:

[0038] S101, The silicon-calcium based material is placed in the SRB bacterial solution for biofilm formation, so that the SRB bacteria are loaded on the silicon-calcium based material to obtain silicon-calcium based biomineralized material;

[0039] S102, the obtained silicon-calcium-based biomineralized material is mixed with antimony-arsenic contaminated soil to remediate the antimony-arsenic contaminated soil.

[0040] The silicon-calcium based material can be any silicon-calcium based material that does not affect the growth of SRB bacteria, and any silicon-calcium based material with adsorption properties that does not affect the growth of SRB bacteria can support SRB bacteria.

[0041] The sulfate-reducing bacteria (SRB) used in this invention are existing bacterial cultures in the prior art; that is, all sulfate-reducing bacteria (SRB) can be used. The culture process of sulfate-reducing bacteria (SRB) is as follows:

[0042] First, prepare the sulfate-reducing bacteria culture medium: yeast extract 1.2 g / L, Ca(NO3)2 0.01 g / L, K2HPO4 0.5 g / L, MgSO4·7H2O 0.5 g / L, KCl 0.1 g / L, and adjust the pH to approximately 6. Then, cultivate the sulfate-reducing bacteria (SRB): In an anaerobic chamber, inoculate the SRB at a 10% inoculum, purge with pure nitrogen for 5 minutes, seal the anaerobic bottle, and incubate at 30°C for 3-5 days. Once the SRB has reached the logarithmic growth phase, it is ready for subsequent experiments.

[0043] The above-mentioned sulfate-reducing bacteria (SRB) is classified as Uncultured sulfate-reducing bacterium SRB-4. The depositary institution is China Center for Type Culture Collection, located at Wuhan University, Wuhan, China. The deposit date is September 14, 2015, and the accession number is CCTCC NO: M2015535.

[0044] This invention employs SRB bacteria and a silicon-calcium-based material to co-immobilize antimony and arsenic, thereby addressing the problems of low immobilization efficiency (removal rate) of antimony and arsenic, and unstable (lack of long-term effectiveness) treatment of arsenic contaminated soil in antimony mining areas. Firstly, a silicon-calcium-based material with adsorption properties and a high specific surface area is placed in the SRB bacterial solution. This material effectively maintains the microbial biomass, meaning it can support a larger amount of SRB bacteria. Since a higher SRB bacteria count leads to a greater immobilization effect on heavy metals in antimony and arsenic contaminated soil, the resulting silicon-calcium-based biomineralization material is mixed with the antimony and arsenic contaminated soil. The surface of the silicon-calcium-based biomineralization material maintains a large number of SRB bacteria, which can produce more hydrogen sulfide. This hydrogen sulfide combines with more heavy metals in the antimony and arsenic contaminated soil to form insoluble metal sulfide precipitates, thus removing the heavy metals from the antimony and arsenic contaminated soil. The effective solidification and removal of antimony and arsenic improves the solidification efficiency of antimony and arsenic contaminated soil remediation. Furthermore, the prepared silicon-calcium-based material possesses a high specific surface area and adsorption efficiency, effectively maintaining microbial biomass and supporting more SRB bacteria, thus increasing the efficiency of heavy metal treatment in the soil. The prepared silicon-calcium-based material contains silicon and calcium, resulting in a high affinity for arsenic. Consequently, the silicon-calcium-based material itself also possesses a certain removal capacity for arsenic in contaminated soil, making the arsenic treatment effect more stable and long-lasting. Additionally, the silicon-calcium-based material contains Fe... 3+ This can further improve the efficiency of arsenic absorption, making the soil treatment effect more long-lasting. In addition, the method provided by this invention is environmentally friendly, does not produce secondary pollution, has low treatment costs, treats waste with waste, can treat a variety of heavy metals (antimony, arsenic, cadmium, lead, zinc, copper, etc.), and is highly practical.

[0045] It should be noted that the remediation method provided by this invention is specifically designed for soils with severely excessive levels of antimony and arsenic, but it can also be used to solidify other metals, such as cadmium, lead, zinc, and copper. The antimony and arsenic cations removed from the soil in this invention are trivalent and pentavalent, respectively.

[0046] Preferably, the silicon-calcium based material is spherical.

[0047] Reference Figure 2 , Figure 2This is a physical image of a silicon-calcium-based material provided by the present invention. In a specific implementation, the silicon-calcium-based material is made into a spherical shape, resulting in a large specific surface area. This allows for a larger contact area with SRB bacteria, enabling the loading of more SRB bacteria. The resulting silicon-calcium-based biomineralized material exhibits a more significant treatment effect on antimony and arsenic contaminated soil, further addressing the problems of low antimony and arsenic solidification efficiency, as well as unstable treatment effects and low removal rates for arsenic.

[0048] Preferably, after mixing the obtained silicon-calcium-based biomineralized material with antimony-arsenic contaminated soil, the method further includes:

[0049] SRB bacterial solution was sprayed onto the antimony and arsenic contaminated soil to remediate the soil.

[0050] In practice, since the amount of SRB bacteria loaded on the silicon-calcium-based biomineralization material (silicon-calcium-based biomineralization pellets) is limited, in order to ensure the soil remediation effect, SRB bacterial solution is periodically sprayed onto the antimony and arsenic contaminated soil mixed with silicon-calcium-based biomineralization material. The periodic spraying is typically done approximately every two weeks, but the specific timing is not limited in this invention.

[0051] Preferably, the film attachment time is 24 h to 48 h.

[0052] In practice, the microorganism SRB attaches to the surface of the silicon-calcium-based material and forms a biofilm, which is called biofilm formation. The biofilm formation time is preferably 24 hours, and at least 24 hours is required to ensure that the surface of the silicon-calcium-based material is completely loaded with SRB.

[0053] In a second aspect, the present invention provides a method for preparing the silicon-calcium based material of the first aspect described above, comprising the following steps:

[0054] S201, fly ash and bentonite are mixed and then ball-milled to obtain a mixture;

[0055] S202, the mixture is subjected to molding treatment to obtain a silicon-calcium based material.

[0056] Fly ash, as a solid waste, is a material mainly composed of calcium aluminum silicate, and its composition includes: SiO2, Al2O3, FeO, Fe2O3, CaO, TiO2, etc.

[0057] Fly ash has a fine particle size, a loose and porous surface, a large specific surface area, and certain active groups. It also naturally possesses alkaline properties, thus exhibiting good adsorption characteristics. (Refer to...) Figure 3 , Figure 3The XRD, SEM, and EDS images of the fly ash are shown in (a), (b), and (c). Analysis demonstrates that the fly ash used in this invention contains a significant amount of calcium magnesium silicate, with most particles approximately 10 micrometers in size and exhibiting a porous surface structure, exhibiting excellent adsorption characteristics. This demonstrates that the fly ash possesses good adsorption capacity. Fly ash is widely available and inexpensive. Using fly ash as a raw material for calcium-silicon-based materials can not only treat antimony and arsenic-contaminated soil but also achieve the goal of treating waste with waste. Furthermore, the silica and calcium components in fly ash have a good affinity for arsenic, resulting in a strong adsorption effect. Consequently, the calcium-silicon-based materials obtained using fly ash as a raw material possess adsorption characteristics, further addressing the problems of unstable arsenic treatment effects and low removal rates.

[0058] The silicon-calcium based material obtained in this embodiment contains silicon and calcium. Therefore, the silicon-calcium based material has a high affinity for arsenic and a strong adsorption effect on arsenic, thus solving the problem of unstable treatment effect on arsenic (lack of long-term effectiveness). The silicon-calcium based material has the characteristics of high specific surface area and adsorption efficiency. It can effectively remove heavy metals in the soil while effectively maintaining the microbial biomass (maintaining the microbial biomass means that the prepared silicon-calcium based material can carry more SRB bacteria. The more microbial biomass, the higher the treatment efficiency of heavy metals in the soil), thus solving the problem of low solidification efficiency of antimony and arsenic when treating soil contaminated in antimony mining areas. The silicon-calcium based material obtained in this invention will not cause secondary pollution to the soil. The reasons are: (1) the fly ash used as raw material is treated to meet the standards before use; (2) the amount of silicon-calcium based material used is not large.

[0059] Preferably, the silicon-calcium based material is spherical.

[0060] In specific implementation, the mixture of ball-milled fly ash and bentonite is placed in a pelletizing machine for molding, producing silica-calcium-based microspheres. It should be noted that the size of the silica-calcium-based material needs to be appropriate; excessively large microspheres should be avoided. Since the raw material for preparing the silica-calcium-based material is powder, a pelletizing machine facilitates its molding; shaping the silica-calcium-based material into small spheres increases its contact area with the SRB bacterial solution. It should be noted that other processing methods besides pelletizing can also be used; this invention does not impose specific limitations.

[0061] Preferably, the molding process of the mixture further includes:

[0062] The mixture is subjected to a molding process, during which Fe is sprayed. 3+ The solution yielded a solution containing Fe. 3+ A silicon-calcium based material; wherein, the Fe 3+ The concentration of the solution is 2 g / L to 10 g / L.

[0063] In practice, Fe is sprayed during the molding process. 3+ The solution can make the obtained Fe-containing 3+ When SRB bacteria are loaded onto a calcium silicate-based material and mixed with antimony- and arsenic-contaminated soil, the adsorption efficiency of arsenic can be further improved, making the soil treatment effect more stable, longer-lasting, and more significant. Specifically, the addition of Fe(III) to the calcium silicate-based biomineralization material can greatly improve the removal effect of As. This may be because Fe(III) can be easily reduced to Fe(II) in the soil environment, and the resulting FeS precipitate adsorbs or co-precipitates As, forming FeAsS precipitate, thereby further improving the removal effect and stability of As.

[0064] Preferably, after step 2, the method further includes:

[0065] The silicon-calcium based material is calcined to obtain the strengthened silicon-calcium based material; wherein the calcination time is 1 h to 2 h and the calcination temperature is 300 ℃ to 500 ℃.

[0066] In practice, the silicon-calcium based material obtained through calcination has high hardness and is easier to treat antimony and arsenic contaminated soil. The preferred calcination time is 2 hours, and the preferred calcination temperature is 300 ℃.

[0067] Preferably, the mass ratio of fly ash to bentonite is 100:10 to 100:1.

[0068] In practice, a mass ratio of fly ash to bentonite of 100:5 is preferred.

[0069] Preferably, the particle size of the mixture is 200 mesh to 500 mesh.

[0070] In practice, the larger the mesh size of the mixture, the finer the particles.

[0071] To enable those skilled in the art to better understand the present invention, the following specific embodiments illustrate the method for remediating antimony and arsenic contaminated soil and the method for preparing silicon-calcium based materials provided by the present invention.

[0072] Example 1

[0073] This embodiment tests the removal efficiency of silicon-calcium-based biomineralization materials for antimony and arsenic in antimony and arsenic solutions. The experimental procedure is as follows:

[0074] A mixed solution containing 10 mg / L of heavy metals As(III) and 20 mg / L of Sb(V) was prepared to simulate water pollution. A Fe solution with a concentration of 5 g / L was also prepared. 3+ Solution.

[0075] Fly ash and bentonite were ground to a particle size of 200-500 mesh, with a fly ash to bentonite mass ratio of 100:5 (g / g). After being mixed evenly, the mixture was placed in a pelletizing machine to obtain silicon-calcium based microspheres. Fe was sprayed during the preparation of the silicon-calcium based microspheres. 3+ Solution, prepared to contain Fe 3+ The obtained silicon-calcium-based microsphere material was calcined in a muffle furnace at 300℃ for 2 h, and then removed after cooling to room temperature. The removed material was then placed in an SRB bacterial solution for 24 h to allow the SRB bacteria to be loaded onto the silicon-calcium-based microspheres, thus obtaining silicon-calcium-based biomineralized microspheres.

[0076] Accurately measure 100 mL of the mixed solution and the prepared silicon-calcium based biomineralization microspheres (approximately 30 microspheres, each about 6 mm in diameter) into an Erlenmeyer flask as the experimental group to test the removal effect of antimony and arsenic. (Refer to...) Figure 4 , Figure 4 The image shows a comparison of the antimony and arsenic removal effects in antimony and arsenic contaminated soil from the antimony mining area in Example 1. It can be seen that the removal rate of antimony in the solution by the Fe3+-containing silicon-calcium-based biomineralization material is 98.8% and 92.6%.

[0077] At the same time, the silicon-calcium based material (containing no Fe) that was not soaked in the SRB bacterial solution was also included. 3+ ), Fe-containing products not soaked in SRB bacterial solution 3+ Silicon-calcium-based materials, and silicon-calcium-based biomineralized materials obtained by immersion in SRB bacterial solution (Fe-free). 3+ Three materials were used as a control group in an experiment with a 100 mL mixed solution to compare their removal effects on antimony and arsenic. It was observed that the method provided in the experimental group showed a significantly better removal effect on antimony and arsenic. The removal effects, from greatest to least, were as follows: The silicon-calcium based biomineralized material (containing no Fe) obtained by soaking in SRB bacterial solution... 3+ ), Fe-containing products not soaked in SRB bacterial solution 3+ Silicon-calcium based materials, and silicon-calcium based materials not soaked in SRB bacterial solution (containing no Fe). 3+ ).

[0078] Example 2

[0079] Contaminated soil from an antimony mining area was selected. The concentration of antimony in the soil was 5447 mg / kg, the concentration of arsenic was 472 mg / kg, the concentration of leached antimony was 7.6 mg / kg, and the concentration of leached arsenic was 0.75 mg / kg.

[0080] Fly ash and bentonite were ground to a particle size of 200-500 mesh, with a fly ash to bentonite mass ratio of 100:5 (g / g). After being mixed evenly, the mixture was placed in a pelletizing machine to obtain silicon-calcium based microspheres. Fe was sprayed during the preparation of the silicon-calcium based microspheres. 3+Solution, prepared to contain Fe 3+ The obtained silicon-calcium-based microsphere material was calcined in a muffle furnace at 300℃ for 2 h, and then removed after cooling to room temperature. The removed material was then placed in an SRB bacterial solution for 24 h to allow the SRB bacteria to be loaded onto the silicon-calcium-based microspheres, thus obtaining silicon-calcium-based biomineralized microspheres.

[0081] The prepared silicon-calcium based biomineralization microspheres were mixed with antimony and arsenic-contaminated soil from an antimony mining area. SRB bacterial solution was periodically sprayed into the soil to investigate the solidification effect on antimony and arsenic in the antimony mining area soil. (Reference) Figure 5 , Figure 5 This is a comparison diagram of the solidification effect of antimony and arsenic in antimony-arsenic contaminated soil in antimony mining area, as shown in Example 2. The soil contains Fe. 3+ The silicon-calcium-based biomineralization material achieved a solidification rate of 93.8% for antimony and 90.3% for arsenic in soil.

[0082] Example 3

[0083] Contaminated soil from an antimony mining area was selected. The concentration of antimony in the soil was 24,666 mg / kg, the concentration of arsenic was 240 mg / kg, the concentration of leached antimony was 13.3 mg / kg, and the concentration of leached arsenic was 0.23 mg / kg.

[0084] Fly ash and bentonite were ground to a particle size of 200-500 mesh, with a fly ash to bentonite mass ratio of 100:5 (g / g). After being mixed evenly, the mixture was placed in a pelletizing machine to obtain silicon-calcium based microspheres. Fe was sprayed during the preparation of the silicon-calcium based microspheres. 3+ Solution, prepared to contain Fe 3+ The obtained silicon-calcium-based microsphere material was calcined in a muffle furnace at 300℃ for 2 h, and then removed after cooling to room temperature. The removed material was then placed in an SRB bacterial solution for 24 h to allow the SRB bacteria to be loaded onto the silicon-calcium-based microspheres, thus obtaining silicon-calcium-based biomineralized microspheres.

[0085] The prepared silicon-calcium based biomineralization microspheres were mixed with antimony and arsenic-contaminated soil from an antimony mining area. SRB bacterial solution was periodically sprayed into the soil to investigate the solidification effect on antimony and arsenic in the antimony mining area soil. (Reference) Figure 6 , Figure 6 This is a comparison diagram of the solidification effect of antimony and arsenic in antimony-arsenic contaminated soil in antimony mining area, Example 3, containing Fe. 3+ The silicon-calcium-based biomineralization material achieved an antimony fixation rate of 88.42% and an arsenic fixation rate of 94.25% in the soil.

[0086] Example 4

[0087] Contaminated soil from an antimony mining area was selected. The concentration of antimony in the soil was 5447 mg / kg, the concentration of arsenic was 472 mg / kg, the concentration of leached antimony was 7.6 mg / kg, and the concentration of leached arsenic was 0.75 mg / kg.

[0088] Fly ash and bentonite were ground to a particle size of 200-500 mesh, with a fly ash to bentonite mass ratio of 100:5 (g / g). After being mixed evenly, the mixture was placed in a pelletizing machine to obtain silicon-calcium based microspheres. Fe was sprayed during the preparation of the silicon-calcium based microspheres. 3+ Solution, prepared to contain Fe 3+ The obtained silicon-calcium-based microsphere material was calcined in a muffle furnace at 300℃ for 2 h, and then removed after cooling to room temperature. The removed material was then placed in an SRB bacterial solution for 24 h to allow the SRB bacteria to be loaded onto the silicon-calcium-based microspheres, thus obtaining silicon-calcium-based biomineralized microspheres.

[0089] The prepared silicon-calcium-based biomineralization pellets and silicon-calcium-based materials not soaked in SRB bacteria were mixed separately with antimony and arsenic-contaminated soil from an antimony mining area. SRB bacteria solution was sprayed into the soil periodically to investigate the solidification effect on antimony and arsenic in the antimony mining area soil. (Reference) Figure 7 , Figure 7 The image shows a comparison of the solidification effects of silicon-calcium-based biomineralized microspheres on antimony and arsenic contaminated soil in antimony mining areas after 20 days in Example 4. The solidification rate of antimony in the soil was 92.68%, and the solidification rate of arsenic was 89.12%. However, the solidification rate of antimony in the soil by the silicon-calcium-based material without SRB bacteria was only 43.79%, and the solidification rate of arsenic was 32.41%.

[0090] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0091] The above provides a detailed description of the method for remediating antimony and arsenic contaminated soil and the preparation method of silicon-calcium based materials provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for remediating antimony and arsenic contaminated soil, characterized in that, Includes the following steps: Step 1: Place the silicon-calcium based material into the SRB bacterial solution for biofilm formation, so that the SRB bacteria are loaded onto the silicon-calcium based material to obtain silicon-calcium based biomineralized material; Step 2: Mix the obtained silicon-calcium-based biomineralized material with antimony-arsenic contaminated soil to remediate the antimony-arsenic contaminated soil; The method for preparing the silicon-calcium based material includes the following steps: Step 101: Mix fly ash and bentonite and then ball mill them to obtain a mixture; Step 102: The mixture is subjected to molding treatment to obtain a silicon-calcium based material; The molding process of the mixture further includes: The mixture is subjected to a molding process, during which Fe is sprayed. 3+ The solution yielded a solution containing Fe. 3+ A silicon-calcium based material; wherein, the Fe 3+ The concentration of the solution is 2 g / L to 10 g / L.

2. The method according to claim 1, characterized in that, The silicon-calcium based material is spherical in shape.

3. The method according to claim 1, characterized in that, After mixing the obtained silicon-calcium-based biomineralized material with antimony-arsenic contaminated soil, the method further includes: SRB bacterial solution was sprayed onto the antimony and arsenic contaminated soil to remediate the soil.

4. The method according to claim 1, characterized in that, The time for the film to attach is 24 h to 48 h.

5. The method according to claim 1, characterized in that, The silicon-calcium based material is spherical in shape.

6. The method according to claim 1, characterized in that, Following step 2, the method further includes: The silicon-calcium based material is calcined to obtain the strengthened silicon-calcium based material; wherein the calcination time is 1 h to 2 h and the calcination temperature is 300 ℃ to 500 ℃.

7. The method according to claim 1, characterized in that, The mass ratio of fly ash to bentonite is 100:10 to 100:

1.

8. The method according to claim 1, characterized in that, The particle size of the mixture is 200 mesh to 500 mesh.

Images