A method for harmless treatment of phosphogypsum

Abstract

This invention discloses a method for the harmless treatment of phosphogypsum, belonging to the field of environmental pollution remediation technology. The method includes drying and pulverizing an emulsion-like phosphogypsum sample to obtain phosphogypsum powder; uniformly mixing the phosphogypsum powder, soil sample, and organic fertilizer in a mass ratio of 7-9:1-3:0.5-1, adding quicklime, and ensuring the pH of the leachate from the mixture is 5-7 to obtain a mixture matrix; spraying the mixture matrix with 15-25 mL of enriching bacterial suspension, placing it in a leachate filtration device, and evenly sprinkling 30-40 g of germinating plant seeds (3-4 days after germination) onto the surface of the mixture matrix, maintaining the moisture content of the mixture matrix at 60-80%, then watering daily at 50-100 mL for ≥14 days, collecting the leachate and measuring its phosphorus and fluorine content. This invention proposes a method for the harmless treatment of phosphogypsum, which, while increasing vegetation coverage in mining areas, solves the problem of excessive phosphorus and fluorine leaching concentrations in phosphogypsum accumulation areas.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental pollution remediation, and in particular relates to a method for harmless treatment of phosphogypsum. Background Art

[0002] With the growth of population and economic development, the demand for phosphate fertilizers in agriculture continues to grow. The extensive development in the past and the over-exploitation of phosphate mineral resources have led to serious soil phosphogypsum pollution, which has become a hot issue that needs to be solved urgently. Usually, the main component of phosphogypsum is CaSO4·2H2O, and it is also accompanied by the risk of pollution from toxic and harmful pollutants such as fluorine, arsenic, copper and radioactive substances. Phosphogypsum piled in the open air will be washed away by rainwater, and environmentally harmful substances will infiltrate and spread to surrounding farmland and groundwater systems through gravity, rainwater erosion and other effects, thus posing a serious threat to the ecological environment around the mining area and the safety of people's drinking water.

[0003] At present, the commonly used methods for phosphogypsum purification and impurity removal mainly include dry neutralization method, lime method, water washing method, flotation method, calcination method, etc., but the shortcomings of various technologies limit their promotion and application. These technical solutions using phosphogypsum are costly, the implementation process is complicated, the amount of phosphogypsum that can be processed is limited, and it does not meet the requirements of sustainable development. In addition, the added treatment agent has the risk of secondary pollution to the environment, so there are still technical methods for harmless treatment of phosphogypsum. Summary of the invention

[0004] The present invention provides a method for harmless treatment of phosphogypsum and develops an ecological restoration technology applied to phosphogypsum mining areas. By combining microorganisms, plants and chemical means, phosphorus and fluorine in phosphogypsum are stabilized, thereby solving the problem of harmless treatment and resource utilization of phosphogypsum and realizing ecological restoration.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for harmless treatment of phosphogypsum, the method comprising the following steps: (1) pretreatment of phosphogypsum waste: after the emulsion phosphogypsum sample is allowed to stand for stratification, the upper clear liquid is filtered to obtain the phosphogypsum leaching solution to measure the pH value; the emulsion phosphogypsum sample is dried, cooled, crushed, and sieved to obtain the phosphogypsum powder for use;

[0006] (2) Preparation of biological bacterial agent: adding the screened bacterial strains to the enrichment culture solution, mixing, activating and culturing for more than 24 hours, to obtain an enriched bacterial suspension; the bacterial strain concentration in the enriched bacterial suspension is 3×10 8 ~4×10 8 cfu / mL;

[0007] (3) Harmless treatment of phosphogypsum: phosphogypsum powder, soil sample and organic fertilizer are uniformly mixed in a mass ratio of 7-9:1-3:0.5-1, and quicklime is added to ensure that the pH of the mixture leachate is 5-7 to obtain a mixture matrix; 15-25 mL of enriched bacterial suspension is sprayed on the mixture matrix, and the mixture matrix is ​​placed in a percolation device to maintain a moisture content of 60-80%. Thereafter, the daily watering amount is 50-100 mL, and the incubation period is ≥14 days. The leachate is collected to detect the P and F contents; after the incubation period, the total phosphorus content of the mixture matrix leachate is ≤2 mg / L, and the fluorine content is ≤0.02 mg / L.

[0008] In step (3) of the present invention, 15 to 25 mL of the enriched bacterial suspension is sprayed on the mixture matrix, which is then placed in a percolation device, and 30 to 40 g of regreening plant seeds after germination for 3 to 4 days are selected and evenly sprinkled on the surface of the mixture matrix, and covered with a small amount of the mixture matrix to maintain the moisture content of the mixture matrix at 60 to 80%. Thereafter, the daily watering amount is 50 to 100 mL, the culture days are ≥8 days, and the leachate is collected to detect the P and F contents: the total phosphorus content is ≤0.01 mg / L, and the total fluorine content is ≤0.01 mg / L.

[0009] In step (3) of the present invention, the regreening plant is an acid-resistant perennial herb.

[0010] In step (3) of the present invention, the regreening plant is any one or more of tall fescue, zoysia grass, vetiver grass, and ryegrass.

[0011] In the step (2) of the present invention, a phosphorus removal bacteria agent carrier is added to the enriched culture solution; the phosphorus removal bacteria agent carrier is an adsorbent rich in porous substances and having stable chemical properties.

[0012] The carrier of the phosphorus removal bacteria agent of the present invention is powder of vermiculite, pumice, zeolite, perlite, coconut shell, wood bark, sawdust, limestone, peat and peat, and the added amount is ≤ 2% of the mass of the enriched bacteria suspension.

[0013] The bacterial species in step (2) of the present invention is any one or more of Pseudomonas sp., Pseudomonas putida, Bacillus subtilis, and Burkholderia.

[0014] In step (1) of the present invention, the initial total phosphorus content in the emulsion phosphogypsum sample leachate is ≥600 mg / L, and the initial fluoride ion content is ≥40 m / L; in step (3), the total phosphorus content in the mixture matrix leachate is ≥45 mg / L; and the fluorine content is ≥35 mg / L.

[0015] The infiltration device in step (3) of the present invention is a container with drainage holes at the bottom, and a tray at the bottom to collect the infiltration liquid flowing out of the drainage holes.

[0016] The organic fertilizer in step (3) of the present invention is any one or more of chicken manure, sheep manure, straw and commercially available organic fertilizer.

[0017] The detection methods of the emulsion phosphogypsum sample, the mixture matrix, and the leachate of the present invention are as follows: Total phosphorus test method: The total phosphorus (TP) content in the collected leachate is determined by using the environmental protection standard "Determination of phosphate and total phosphorus in water - continuous flow-ammonium molybdate spectrophotometry" (HJ670-2013), and the analysis is performed on the AutoAnalyzer 3 continuous flow chemical analyzer. Fluoride test method: The environmental protection standard "Water quality inorganic anions (F - , Cl - 、NO2 - Br - 、NO3 - Determination of fluoride ions (F - ) content, tested and analyzed on an ion chromatograph.

[0018] In step (3) of the present invention, the strain screening method is as follows: take a soil sample rich in phosphogypsum waste, dissolve and mix it with water, take 15 mL of the fully mixed sample solution and inject it into a triangular flask containing 100 mL of enrichment culture medium, and culture it at a constant temperature of 30°C for 1 to 3 days. When the culture medium becomes turbid, absorb 8 mL of the culture solution and transfer it to the enrichment culture medium, and continue to culture it under the same shaking conditions for 1 to 3 days, and repeat this process. The transfer amount each time is 4 mL, 2 mL, 1 mL, and 0.5 mL, respectively, and the content of potassium dihydrogen phosphate in the enrichment culture medium is appropriately increased each time, and the contents are successively: 2 mg, 5 mg, 8 mg, 10 mg, 15 mg, and 20 mg; the components of the enrichment culture medium are: 2.0 g (NH4) SO4, 0.5 g MgSO4·7H2O, 5.0 g anhydrous sodium acetate, 0.2 g CaCl2, 2 to 20 mg KH2PO4, distilled water to 1000 mL, and a pH value of 7.2 to 7.4.

[0019] The beneficial effect of adopting the above technical solution is that: the present invention combines the actual status of the polluted site and proposes a biological / bio-chemical method for harmless treatment of phosphogypsum that combines microorganisms and plants according to local conditions. A variety of technical means are used for coordinated repair, and ultimately the content of P and F elements in soil leachate is reduced, thereby achieving purification of groundwater sources. The selected plants also play a role in ecological restoration of the contaminated site. The research results provide basic theoretical and technical support for the comprehensive utilization of phosphogypsum, and while increasing the vegetation coverage rate in the mining area, effectively solve the problem of excessive leaching concentrations of phosphorus and fluorine elements in the phosphogypsum accumulation area. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below in conjunction with specific embodiments.

[0021] Example 1

[0022] A method for harmless treatment of phosphogypsum comprises the following steps:

[0023] (1) Pretreatment of phosphogypsum waste: After the emulsion phosphogypsum sample is allowed to stand for stratification, the upper clear liquid is filtered to obtain the phosphogypsum leaching solution and the pH value is measured; another emulsion phosphogypsum sample is taken, placed in an oven at 120°C for 120 min for drying, and then crushed after cooling, and passed through a 2 mm sieve to obtain phosphogypsum powder for use;

[0024] (2) Preparation of biological bacterial agent: The selected bacterial strains (Pseudomonas and Pseudomonas putida mixed in equal proportions) were added to the enriched culture solution and mixed. After activation and culture for more than 24 hours, an enriched bacterial suspension was obtained. Vermiculite powder, a carrier of the phosphorus removal bacterial agent, was added at 1% of the mass of the enriched culture solution. The bacterial strain concentration in the enriched bacterial suspension was 3.5×10 8 cfu / mL;

[0025] (3) Harmless treatment of phosphogypsum: Phosphogypsum powder, soil sample, and organic fertilizer (commercially available organic fertilizer) were uniformly mixed in a mass ratio of 9:1:0.8, and quicklime was added to ensure that the pH of the leachate of the mixture was 6 to obtain a mixture matrix; three groups of experiments were carried out simultaneously, namely, a blank control "sterile and grassless" group: no addition of any substance; a "sterile and grassless" group: spraying 20 mL of enriched bacterial suspension; a "sterile and grass" group: spraying 20 mL of enriched bacterial suspension, selecting 40 g of regreening plant seeds (the regreening plant is a mixture of tall fescue, zoysia grass, etc. in a mass ratio) that had germinated for 3 to 4 days and evenly sprinkled on the surface of the mixture matrix, and then covered with a small amount of the mixture matrix.

[0026] The mixture matrix was placed in a percolation device, the moisture content of the mixture matrix was maintained at 60%, and then 50-100 mL of water was applied daily. The culture period was 14 days, and the percolation liquid was collected and filtered through a 0.45 μm filter membrane to detect the P and F contents.

[0027] (4) Experimental results:

[0028] Emulsion phosphogypsum sample: total phosphorus content 633.85 mg / L; fluorine content 40.33 mg / L.

[0029] Mixture matrix: total phosphorus content 49.06 mg / L; fluorine content 39.22 mg / L.

[0030] The blank control "sterile and grass-free" group: total phosphorus content was 14.38 mg / L, and fluorine content was 37.15 mg / L.

[0031] “With bacteria but without grass” group: total phosphorus content 1.64 mg / L, fluorine content 0.24 mg / L.

[0032] "With bacteria and grass" group: total phosphorus content 0.098 mg / L, meeting the national standard GB 383830-2002 for Class I water bodies for total phosphorus concentration limit (0.02 mg / L); fluoride content 0 mg / L (10th day), meeting the national standard GB / T 14848-2017-2002 for Class I water bodies for fluoride ion concentration limit.

[0033] Example 2

[0034] A method for harmless treatment of phosphogypsum comprises the following steps:

[0035] (1) Pretreatment of phosphogypsum waste: After the emulsion phosphogypsum sample is allowed to stand for stratification, the upper clear liquid is filtered to obtain the phosphogypsum leaching solution and the pH value is measured; another emulsion phosphogypsum sample is taken, placed in an oven at 120°C for 120 min for drying, and then crushed after cooling, and passed through a 2 mm sieve to obtain phosphogypsum powder for use;

[0036] (2) Preparation of biological agent: The selected strain (Bacillus subtilis) was added to the enrichment culture solution and mixed. After activation and culture for more than 24 hours, an enrichment suspension was obtained. Peat powder, a carrier of the phosphorus removal agent, was added at a concentration of 2% of the mass of the enrichment culture solution. The strain concentration in the enrichment suspension was 4×10 8 cfu / mL;

[0037] (3) Harmless treatment of phosphogypsum: Phosphogypsum powder, soil sample, and organic fertilizer (mixture of chicken manure, sheep manure, etc.) were uniformly mixed in a mass ratio of 8:2:1, and quicklime was added to ensure that the pH of the leachate of the mixture was 7 to obtain a mixture matrix. Three groups of experiments were carried out simultaneously, namely the blank control "sterile and grassless" group: no addition of any substance; the "sterile and grassless" group: spraying 25 mL of enriched bacterial suspension; the "sterile and grass" group: spraying 25 mL of enriched bacterial suspension, selecting 3-4 days after germination of regreening plant seeds (the regreening plant is vetiver) and evenly sprinkling 35 g on the surface of the mixture matrix, and covering it with a small amount of the mixture matrix.

[0038] The specific operation method is: put the mixture matrix into the infiltration device, keep the moisture of the mixture matrix at 80%, then water it with 50-100 mL per day, culture it for 14 days, collect the infiltrate, filter it through a 0.45 μm filter membrane, and then detect the P and F contents.

[0039] (4) Experimental results:

[0040] Emulsion phosphogypsum sample: total phosphorus content 633.85 mg / L; fluorine content 40.33 mg / L.

[0041] Mixture matrix: total phosphorus content 47.55 mg / L; fluorine content 39.22 mg / L.

[0042] Blank control "sterile and grass-free" group: total phosphorus content 11.35 mg / L, fluorine content 35.55 mg / L.

[0043] “With bacteria but without grass” group: total phosphorus content 1.53 mg / L, fluorine content 0.02 mg / L.

[0044] "With bacteria and grass" group: total phosphorus content 0 mg / L, meeting the national standard GB 383830-2002 for Class I water bodies for total phosphorus concentration limit (0.02 mg / L); fluoride content 0 mg / L (9th day), meeting the national standard GB / T14848-2017-2002 for Class I water bodies for fluoride ion concentration limit.

[0045] Example 3

[0046] A method for harmless treatment of phosphogypsum comprises the following steps:

[0047] (1) Pretreatment of phosphogypsum waste: After the emulsion phosphogypsum sample is allowed to stand for stratification, the upper clear liquid is filtered to obtain the phosphogypsum leaching solution and the pH value is measured; another emulsion phosphogypsum sample is taken, placed in an oven at 120°C for 120 min for drying, and then crushed after cooling, and passed through a 2 mm sieve to obtain phosphogypsum powder for use;

[0048] (2) Preparation of biological agent: The selected strain (Burkholderia) was added to the enrichment culture solution and mixed. After activation and culture for more than 24 hours, an enriched bacterial suspension was obtained. The strain concentration in the enriched bacterial suspension was 3.5×10 8 cfu / mL;

[0049] (3) Harmless treatment of phosphogypsum: Phosphogypsum powder, soil sample, and organic fertilizer (chicken manure) were uniformly mixed in a mass ratio of 7:3:0.5, and quicklime was added to ensure that the pH of the leachate of the mixture was 5 to obtain a mixture matrix; three groups of experiments were carried out simultaneously, namely, the blank control "sterile and grassless" group: no addition of any substance; the "sterile and grassless" group: spraying 15 mL of enriched bacterial suspension; the "sterile and grass" group: spraying 15 mL of enriched bacterial suspension, selecting 3-4 days after germination of regreening plant seeds (the regreening plant is a mixture of tall fescue, ryegrass, etc. in a mass ratio) and evenly sprinkling 30 g on the surface of the mixture matrix, and covering it with a small amount of the mixture matrix.

[0050] The specific operation method is: put the mixture matrix into the infiltration device, maintain the moisture content of the mixture matrix at 70%, then water it with 50-100 mL per day, culture it for 14 days, collect the infiltrate, filter it through a 0.45 μm filter membrane, and then detect the P and F contents.

[0051] (4) Experimental results:

[0052] Emulsion phosphogypsum sample: total phosphorus content 633.85 mg / L; fluorine content 40.33 mg / L.

[0053] Mixture matrix: total phosphorus content 45.03 mg / L; fluorine content 39.22 mg / L.

[0054] Blank control "sterile and grass-free" group: total phosphorus content 8.32 mg / L, fluorine content 31.11 mg / L.

[0055] “With bacteria but without grass” group: total phosphorus content 0.8 mg / L, fluorine content 0.01 mg / L.

[0056] "With bacteria and grass" group: total phosphorus content is 0 mg / L, which meets the national standard GB 383830-2002 for Class I water bodies for total phosphorus concentration limit (0.02 mg / L); fluoride content is 0 mg / L (8th day), which meets the national standard GB / T14848-2017-2002 for Class I water bodies for fluoride ion concentration limit.

[0057] By comparing the above examples 1-3, it can be seen that the P and F contents in the leachate of the phosphogypsum treated by the method of the present invention are greatly reduced, and the P and F are reused or solidified in microorganisms or plants, and no longer pollute the groundwater source. The "bacteria without grass" group and the "bacteria with grass" remediation technology can more efficiently treat phosphorus and fluorine in phosphogypsum, and effectively solve the problem of excessive P and F concentrations in the leachate of phosphogypsum.

[0058] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for harmless treatment of phosphogypsum, characterized in that: The method comprises the following steps: (1) Pretreatment of phosphogypsum waste: drying the emulsion phosphogypsum sample, cooling it, crushing it, and sieving it to obtain phosphogypsum powder for later use; (2) Preparation of biological bacterial agent: adding the screened bacterial strains to the enrichment culture solution, mixing, activating and culturing for more than 24 hours, and obtaining an enriched bacterial suspension; the bacterial strain concentration in the enriched bacterial suspension is 3×10 8 ~4×10 8 cfu / mL; (3) Harmless treatment of phosphogypsum: evenly mix phosphogypsum powder, soil sample and organic fertilizer in a mass ratio of 7-9:1-3:0.5-1, add quicklime, ensure that the pH of the mixture leachate is 5-7, and obtain a mixture matrix; spray 15-25 mL of enriched bacterial suspension on the mixture matrix, put it into the infiltration device, keep the moisture content of the mixture matrix at 60-80%, then water it with 50-100 mL per day, cultivate it for ≥14 days, collect the leachate to detect the P and F content; after the cultivation, the total phosphorus content of the mixture matrix leachate is ≤2 mg / L, and the fluorine content is ≤0.02 mg / L; In the step (1), the initial total phosphorus content in the emulsion phosphogypsum sample leachate is ≥600 mg / L, and the initial fluoride ion content is ≥40 mg / L; In the step (3), the mixture matrix is ​​sprayed with 15-25 mL of the enriched bacterial suspension, placed in a percolation device, 30-40 g of regreening plant seeds after germination for 3-4 days are selected and evenly sprinkled on the surface of the mixture matrix, and covered with a small amount of the mixture matrix to maintain the moisture content of the mixture matrix at 60-80%. After that, the daily watering amount is 50-100 mL, the culture days are ≥8 days, and the leachate is collected to detect the P and F contents: the total phosphorus content is ≤0.01 mg / L, and the total fluorine content is ≤0.01 mg / L; In step (3), the regreening plant is any one or more of tall fescue, zoysia grass, vetiver grass, and ryegrass; The bacterial species in step (2) is any one or more of Pseudomonas putida, Bacillus subtilis and Burkholderia.

2. The method for harmless treatment of phosphogypsum according to claim 1, characterized in that: In the step (2), a phosphorus removal bacteria agent carrier is added to the enriched culture solution; the phosphorus removal bacteria agent carrier is an adsorbent rich in porous substances and having stable chemical properties.

3. The method for harmless treatment of phosphogypsum according to claim 2, characterized in that: The carrier of the phosphorus removal bacteria agent is powder of vermiculite, pumice, zeolite, perlite, coconut shell, wood bark, sawdust, limestone, peat and peat, and the added amount is ≤ 2% of the mass of the enriched bacteria suspension.

4. A method for harmless treatment of phosphogypsum according to any one of claims 1 to 3, characterized in that: In the step (3), in the mixture matrix leachate: the total phosphorus content is ≥45 mg / L; the fluorine content is ≥35 mg / L.

5. A method for harmless treatment of phosphogypsum according to any one of claims 1 to 3, characterized in that: The infiltration device in step (3) is a container with drainage holes at the bottom and a tray at the bottom to collect the leachate flowing out of the drainage holes.

6. A method for harmless treatment of phosphogypsum according to any one of claims 1 to 3, characterized in that: The organic fertilizer in step (3) is any one or more of chicken manure, sheep manure, straw and commercially available organic fertilizer.