Green, environment-friendly and harmless synergistic treatment method for ardealite

Abstract

The invention belongs to the technical field of phosphorus chemical industry, and particularly discloses a green, environment-friendly and harmless synergistic treatment method of phosphogypsum, which comprises the following steps: stirring phosphogypsum and a biological modified solution in proportion for reaction to obtain mixed slurry; carrying out solid-liquid separation on the mixed slurry, filtering the liquid and then outputting, then adding the biological modification solution again, and circularly repeating the steps to carry out biological modification treatment; after biological modification is finished, carrying out solid-liquid separation to obtain harmless phosphogypsum; adding a precipitant into the liquid obtained by solid-liquid separation in proportion, and stirring for reaction to obtain harmless liquid; and the harmless liquid is directly discharged or flows back to the biological modified solution storage tank for recycling. The MICP technology is utilized to generate calcium carbonate precipitates and dissolve out phosphorus, fluorine and heavy metal, then the precipitant is added to precipitate phosphorus and fluorine, the heavy metal and carbonate are combined and precipitated, green and environment-friendly harmless treatment of phosphogypsum is achieved, and the method has the advantages of being high in treatment efficiency, neutral in product pH, high in resource recovery rate and good in economical efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphorus chemical industry, and particularly relates to a green and environmentally friendly harmless collaborative treatment method for phosphogypsum with high treatment efficiency, neutral product pH, high resource recovery rate and good economy. Background Art

[0002] Phosphogypsum is an industrial solid waste generated in the production process of wet-process phosphoric acid. For every 1 ton of phosphoric acid produced, 4 - 6 tons of phosphogypsum will be generated. The main component of phosphogypsum is CaSO 4 ·2H 2 O. In addition, it also contains undecomposed phosphate rock and impurities such as unremoved phosphoric acid, fluorine, heavy metals, and radionuclides. Moreover, it has strong acidity and fine particles. Traditional stacking will cause problems such as heavy metal pollution of lakes and groundwater, water eutrophication, and air pollution, seriously threatening human health and life safety. Therefore, it has become an urgent need to harmlessly treat phosphogypsum, especially to remove or utilize resources such as phosphorus and fluorine therein.

[0003] At present, the harmless treatment methods of phosphogypsum are mainly divided into physical methods, chemical methods and biological methods. Among them, physical methods mainly remove impurities through physical means (such as washing with water, flotation, ball milling, etc.), but it is difficult to fundamentally change the chemical properties of phosphogypsum. Chemical methods remove harmful components through chemical reactions (such as acid leaching, precipitation, redox, etc.), but usually a large amount of chemical reagents such as strong acids and strong bases are required, and the process is complex, requiring precise control of reaction conditions, and the waste residues after treatment also need to be properly treated. Biological methods use the metabolic action of microorganisms to remove harmful components, but the treatment speed is slow, and the treatment effect on high-concentration pollutants is limited.

[0004] In the prior art, in order to solve the environmental problems caused by the stacking of phosphogypsum, phosphogypsum is mixed with cement, alkali-activated cementitious materials and other cementitious materials to prepare a phosphogypsum filling body for the backfill of mines. However, due to the high cost of cement, alkali-activated cementitious materials and other cementitious materials, and the filling body is strongly alkaline for a long time, which is easy to cause environmental pollution. In addition, the soluble fluorine, phosphorus pentoxide and heavy metal content in the phosphogypsum filling body are relatively high, which is easy to cause groundwater pollution. Therefore, a cementitious solution formed by an aqueous solution of urea and calcium chloride, and a Bacillus pasteurii bacterial solution are mixed and reacted with phosphogypsum, the supernatant of the slurry after the reaction is separated, and then a mixed solution formed by the bacterial solution and the cementitious solution is added. After stirring and mixing evenly, continuous aeration is carried out to maintain the microbial activity. Then, after adding the mixed solution 4 to 6 times, a phosphogypsum filling slurry is obtained. Although the soluble fluorine and phosphorus pentoxide in the phosphogypsum filling slurry are significantly reduced compared with the process without adding the bacterial solution, its supernatant is not effectively treated, resulting in a great environmental risk of discharging the supernatant containing high concentrations of soluble fluorine, phosphorus pentoxide and heavy metals. Moreover, after separating the supernatant, 4 to 6 times of biological modification treatment are required, and each biological modification treatment takes 3 to 5 days, resulting in a complete biological modification treatment taking 12 to 30 days, with extremely low treatment efficiency and relatively cumbersome operation. In addition, there are also biological methods such as the activated sludge method that uses microbial communities to degrade soluble phosphates and convert them into bioavailable forms (such as polyphosphates); the anaerobic-aerobic combined process that promotes denitrification bacteria to denitrify under anaerobic conditions and strengthens the adsorption and precipitation of phosphorus in the aerobic stage; and the biosorption method that uses specific microorganisms (such as sulfate-reducing bacteria, Bacillus) to adsorb heavy metal ions through extracellular polymers to reduce the toxicity of wastewater. However, the above methods are currently mostly limited to the laboratory scale, lacking large-scale engineering cases, and the treatment efficiency and stability are also insufficient. There are also deficiencies such as the need to precisely regulate the microbial community structure and metabolic pathway, resulting in a relatively high technical threshold for operation and maintenance, and the complex design of the bioreactor, which requires the combination of wastewater treatment systems or solid waste pretreatment processes. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a green, environmentally friendly and harmless collaborative treatment method for phosphogypsum with high treatment efficiency, neutral product pH, high resource recovery rate and good economy.

[0006] The present invention is realized as follows: it includes steps of slurry preparation, cyclic modification, solid output, precipitation treatment, and liquid disposal. The specific contents are as follows: A. Slurry preparation: Phosphogypsum and a biological modification solution are transported to a reaction device in proportion and stirred for reaction to prepare a mixed slurry. B. Cyclic modification: Separate the solid-liquid mixture in the reaction device, and filter and output the liquid from the bottom of the reaction device; then add the biological modification solution into the reaction device at least once in a cycle, and perform the biological modification treatment operation of solid-liquid separation after stirring and reacting according to step A. C. Output of solid: After step B completes the predetermined biological modification treatment operation, take out the solid obtained by solid-liquid separation, and thus obtain harmless phosphogypsum. D. Precipitation treatment: Transport the liquid obtained by solid-liquid separation in steps B and C to the liquid harmless treatment device, add a precipitant in proportion, and obtain harmless liquid after stirring and reacting. E. Liquid disposal: Directly discharge the harmless liquid or recycle it back to the biological modification solution storage tank for reuse.

[0007] Furthermore, in step A, the ratio of the biological modification solution is: peptone 5 g / L, tryptone 15 g / L, sodium chloride 5 g / L, urea 60 - 90 g / L, and the liquid of Bacillus pasteurii with an OD600 value of 1 - 2; the solid-liquid mass ratio of the phosphogypsum to the biological modification solution is (2 - 1):1.

[0008] Furthermore, in step A, the biological modification solution is obtained by activating Bacillus pasteurii, inoculating 1 V% of Bacillus pasteurii in a liquid medium containing peptone 5 g / L, tryptone 15 g / L, sodium chloride 5 g / L, and urea 60 - 90 g / L for cultivation, and obtaining the liquid of Bacillus pasteurii with an OD600 value of 1 - 2.

[0009] Furthermore, in step A, the phosphogypsum and the biological modification solution are stirred and reacted at a reaction temperature of 30 °C and a pH of 7 - 8 in the reaction device at 300 - 500 rpm for 20 - 24 h.

[0010] Furthermore, in step B, the biological modification treatment operation is cycled 1 - 3 times.

[0011] Furthermore, in steps B and C, solid-liquid separation is carried out until no liquid flows out from the bottom of the suction filtration mechanism at the bottom of the reaction device.

[0012] Furthermore, in step D, the precipitant is calcium chloride, and the addition amount of calcium chloride is 8 - 10% of the total mass of the solution after addition.

[0013] Furthermore, the calcium chloride and the liquid obtained by solid-liquid separation are stirred and reacted at room temperature and 300 - 500 rpm in the liquid harmless treatment device for 0.5 - 2 h.

[0014] Furthermore, after the calcium chloride and the liquid obtained by solid-liquid separation are stirred and reacted, they are filtered to obtain harmless liquid and filter residue, and the filter residue further recovers phosphorus, fluorine and heavy metals therein.

[0015] Further, in step E, the harmless liquid is recycled back to the biological modification solution storage tank for reuse. Specifically, the harmless liquid is returned to the biological modification solution storage tank at a ratio of 30% - 50% of the total mass of the liquid in the storage tank, and the pH value of the harmless liquid is adjusted to be the same as that of the biological modification solution before returning.

[0016] Advantages of the present invention: 1. The present invention uses biological and chemical methods to synergistically treat phosphogypsum. First, based on the Microbially Induced Calcium Carbonate Precipitation (MICP) technology, through the interaction between the biological modification solution and phosphogypsum, different cycles of treatment are carried out. This not only effectively dissolves and releases phosphoric acid, fluorine, and heavy metals in phosphogypsum into the solution, thus purifying phosphogypsum, but also generates more stable, harmless, and recyclable calcium carbonate precipitation, effectively demonstrating the advantages of environmental friendliness and cost control of the microbial treatment technology in phosphogypsum treatment. Then, combined with chemical precipitants, phosphorus and fluorine in the solution are precipitated and removed in solid form, while heavy metals are precipitated and removed by combining with the remaining carbonate and calcium chloride, and resources such as phosphorus and fluorine can be further recovered, also demonstrating the characteristics of high treatment efficiency and easy control of treatment products of the chemical method. Finally, the harmless treatment of phosphogypsum is achieved, and the entire treatment process maintains a neutral pH, without the need for traditional strong acids and strong bases and other chemicals, so the relative cost is low and there is no environmental pollution after discharge.

[0017] 2. The present invention combines a specific formulation of Bacillus pasteurii bacterial solution (containing soy peptone / casein peptone / sodium chloride / urea, etc.). Through 1 - 3 cycles (20 - 24 h / cycle) of biological modification treatment, that is, it can effectively dissolve phosphoric acid, fluorine, and heavy metals in phosphogypsum in up to 3 days, and can convert phosphogypsum into recyclable calcium carbonate precipitation. And it only takes 0.5 - 2 h to precipitate and remove phosphorus, fluorine, and heavy metals in the solution in solid form through chemical precipitants. Therefore, compared with the existing biological modification treatment which takes 12 - 30 days, the present invention significantly improves the treatment efficiency. At the same time, the integration of the solid-liquid separation function in the reaction device simplifies the operation process.

[0018] 3. The present invention uses calcium chloride precipitant to deeply purify the solution after biological modification treatment, which can precipitate and remove phosphorus, fluorine, and heavy metals in the solution, thus achieving the discharge or reuse of wastewater up to the standard, and completely solving the environmental pollution risk existing in the discharge of the solution after the existing biological method treatment.

[0019] 4. The calcium carbonate precipitate after biological modification of the present invention is stable in nature and low in harmful components, and can be utilized as a resource, while the filter residue obtained by chemical precipitation can further recover phosphorus, fluorine and heavy metal resources, thereby improving the comprehensive utilization rate of resources; and the present invention uses urea to replace the high-priced gelling material of the phosphogypsum filling body, combined with the bacterial liquid circulation culture technology, which can effectively reduce the processing cost; and the present invention firstly performs biological modification and solid-liquid separation, which significantly reduces the processing volume of chemical precipitation, can effectively reduce the consumption of reagents, and thus further reduces the processing cost.

[0020] 5. The process parameters of the biological modification treatment of the present invention are clear, the reaction conditions are mild (basically operated at room temperature), and the equipment compatibility is strong (conventional stirring + filtering device), which overcomes the traditional biological method's reliance on precise control of the bacterial flora and is suitable for industrial continuous production.

[0021] In summary, the present invention achieves the harmless treatment of phosphogypsum through the synergistic effect of biological and chemical methods, and has the advantages of high treatment efficiency, neutral product pH, high resource recovery rate and good economy, providing a new and more effective solution for the harmless treatment of phosphogypsum. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the phosphogypsum processing principle of the present invention; In the figure: 1-reaction device, 2-filtration mechanism, 3-liquid harmless device, 4-aeration device, 5-harmless phosphogypsum collection device, 6-phosphogypsum storage tank, 7-biological modification solution storage tank. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] like Figure 1 As shown, the present invention includes the steps of slurry preparation, circulation modification, solid output, precipitation treatment, and liquid disposal, and the specific contents are as follows: A. Slurry preparation: transporting phosphogypsum and bio-modified solution to a reaction device in proportion and stirring to react to prepare a mixed slurry; B. Circulation modification: the mixed slurry in the reaction device is separated into solid and liquid, and the liquid is filtered and discharged from the bottom of the reaction device; then the biological modification solution is added to the reaction device at least once, and the biological modification treatment operation of solid-liquid separation is performed after stirring the reaction according to step A; C. Outputting solids: After the predetermined biological modification treatment operation is completed in step B, the solids obtained by solid-liquid separation are taken out to obtain harmless phosphogypsum; D. Precipitation treatment: The liquid obtained by solid-liquid separation in steps B and C is transported to a liquid harmless treatment device, and a precipitant is added in proportion. After stirring and reacting, harmless liquid is obtained. E. Liquid disposal: The harmless liquid is directly discharged or recycled to the biological modification solution storage tank for reuse.

[0025] In step A, the formulation of the biological modification solution is as follows: 5 g / L of soy peptone, 15 g / L of casein peptone, 5 g / L of sodium chloride, 60 - 90 g / L of urea, and a Bacillus pasteurii bacterial solution with an OD600 value of 1 - 2; the solid-liquid mass ratio of the phosphogypsum to the biological modification solution is (2 - 1):1.

[0026] In step A, the biological modification solution is obtained by activating Bacillus pasteurii and then inoculating 1 V% of Bacillus pasteurii in a liquid medium containing 5 g / L of soy peptone, 15 g / L of casein peptone, 5 g / L of sodium chloride, and 60 - 90 g / L of urea for cultivation to obtain a Bacillus pasteurii bacterial solution with an OD600 value of 1 - 2.

[0027] In step A, the phosphogypsum and the biological modification solution are stirred and reacted at a reaction temperature of 30 °C and a pH of 7 - 8 at 300 - 500 rpm for 20 - 24 h in a reaction device.

[0028] In step B, the biological modification treatment operation is cycled 1 - 3 times.

[0029] In steps B and C, solid-liquid separation is carried out until no liquid flows out from the bottom of the suction filtration mechanism at the bottom of the reaction device.

[0030] In step D, the precipitant is calcium chloride, and the addition amount of calcium chloride is 8 - 10% of the total mass of the solution after addition.

[0031] The calcium chloride and the liquid obtained by solid-liquid separation are stirred and reacted at room temperature and 300 - 500 rpm for 0.5 - 2 h in the liquid harmless treatment device.

[0032] After the calcium chloride and the liquid obtained by solid-liquid separation are stirred and reacted, they are filtered to obtain harmless liquid and filter residue, and the filter residue is further recycled for phosphorus, fluorine, and heavy metals therein.

[0033] In step E, when the harmless liquid is recycled to the biological modification solution storage tank for reuse, the harmless liquid is returned to the biological modification solution storage tank at a ratio of 30 - 50% of the total mass of the liquid in the storage tank, and the pH value of the harmless liquid is adjusted to be the same as that of the biological modification solution before returning.

[0034] The reuse ratio of the harmless liquid is dynamically adjusted according to its water quality (COD, ion concentration).

[0035] Example 1

[0036] S100: Feed phosphogypsum and the biological modification solution into the reaction device 1 at a solid-liquid mass ratio of 1:1, and stir and react at 30 °C and a pH of 7 - 8 for 24 h at 300 rpm to prepare a mixed slurry.

[0037] Among them, the biological modification solution is obtained by activating Bacillus pasteurii and inoculating 1 V% Bacillus pasteurii in a liquid medium containing 5 g / L of soy peptone, 15 g / L of casein peptone, 5 g / L of sodium chloride, and 60 g / L of urea for cultivation to obtain a Bacillus pasteurii bacterial solution with an OD600 value of 1.

[0038] S200: Separate the solid and liquid of the mixed slurry in the reaction device 1 until no more liquid flows out from the suction filtration mechanism 2 at the bottom. The liquid is filtered from the bottom of the reaction device and then output; then, the biological modification treatment operation of adding the biological modification solution into the reaction device 1 once and stirring and reacting according to the steps of S100 and then separating the solid and liquid is cycled.

[0039] S300: After completing the predetermined biological modification treatment operation in step S200, separate the solid and liquid until no more liquid flows out from the suction filtration mechanism 2 at the bottom of the reaction device 1, take out the obtained solid, and thus obtain harmless phosphogypsum and output it to the harmless collection device 5.

[0040] S400: Feed the liquid separated from the solid and liquid in steps S200 and S300 into the liquid harmless device 3, add calcium chloride as a precipitant in proportion (the addition amount of calcium chloride is 8% of the total mass of the solution after addition), stir and react at 300 - 500 rpm at room temperature for 0.5 h and then filter to obtain harmless liquid and filter residue.

[0041] S500: Directly discharge or recycle the harmless liquid, and further recover phosphorus, fluorine, and heavy metals from the filter residue.

[0042] Perform toxicity leaching experiments on the harmless phosphogypsum obtained in step S300, the liquid separated from the solid and liquid in steps S200 and S300, and the finally obtained harmless liquid respectively. At the same time, measure phosphorus, fluorine, and pH in the harmless liquid. The results are shown in Table 1.

[0043] Table 1 Results of toxicity leaching experiments

[0044] As can be seen from Table 1: 1) The pH value of the non-hazardous phosphogypsum toxic leaching liquid is 6.90, close to neutral, indicating that the phosphogypsum after non-hazardous treatment has little impact on the acidity and alkalinity of water bodies during the leaching process. The pH value of the liquid is 7.93, showing weak alkalinity, but still meeting the requirements of GB 8978-1996. The pH value of the non-hazardous liquid is 7.13, close to neutral, indicating that after precipitation treatment, the acidity and alkalinity of the liquid tend to be stable, meeting environmental protection requirements.

[0045] 2) The phosphorus content in the non-hazardous phosphogypsum toxic leaching liquid is 0.719 mg / L, far lower than the phosphorus content of 129.000 mg / L in the toxic leaching liquid of the original phosphogypsum, indicating that the non-hazardous treatment effectively reduces the phosphorus leaching amount. The phosphorus content in the liquid is 12.240 mg / L, indicating that during the biological modification process, phosphorus is dissolved and released into the solution. The phosphorus content in the non-hazardous liquid is 9.36 mg / L. After precipitation treatment, the phosphorus content is further reduced, and the phosphorus content meets the requirements of GB 8978-1996.

[0046] 3) The fluorine content in the non-hazardous phosphogypsum toxic leaching liquid is 3.48 mg / L, far lower than the fluorine content of 8.13 mg / L in the toxic leaching liquid of the original phosphogypsum, indicating that the non-hazardous treatment effectively reduces the fluorine leaching amount. The fluorine content in the liquid is 13.36 mg / L, indicating that during the biological modification process, fluorine is dissolved and released into the solution. The fluorine content in the non-hazardous liquid is 0.006 mg / L. After precipitation treatment, the fluorine content is significantly reduced and almost undetectable, indicating that the precipitant has a very good effect on removing fluorine.

[0047] In summary, the non-hazardous treatment in Example 1 effectively reduces the phosphorus and fluorine contents in the toxic leaching liquid of phosphogypsum, and the pH value of the treated liquid is close to neutral, meeting environmental protection requirements. It shows that this method has a significant effect in removing harmful substances.

[0048] Example 2

[0049] S100: The phosphogypsum and the biological modification solution are transported to the reaction device 1 at a solid-liquid mass ratio of 2:1, and stirred and reacted at 500 rpm for 20 h under the conditions of a reaction temperature of 30 °C and a pH of 7-8 to prepare a mixed slurry.

[0050] Among them, the biological modification solution is obtained by activating Bacillus pasteurii and inoculating 1 V% of Bacillus pasteurii in a liquid medium containing 5 g / L of soy peptone, 15 g / L of casein peptone, 5 g / L of sodium chloride, and 90 g / L of urea for cultivation to obtain a Bacillus pasteurii bacterial solution with an OD600 value of 2.

[0051] S200: The mixed slurry in the reaction device 1 is separated into solid and liquid until no more liquid flows out of the suction filtration mechanism 2 at the bottom, and the liquid is filtered and output from the bottom of the reaction device; then the biological modification solution is added to the reaction device 1 in two cycles, and the biological modification treatment operation of solid-liquid separation is performed after stirring the reaction according to step S100.

[0052] S300: After the predetermined biological modification treatment operation is completed in step S200, the solid and liquid are separated until no more liquid flows out of the suction filtration mechanism 2 at the bottom of the reaction device 1, and the obtained solid is taken out, that is, the harmless phosphogypsum is obtained and output to the harmless collection device 5.

[0053] S400: The liquid obtained by solid-liquid separation in steps S200 and S300 is transported to the liquid harmless device 3, calcium chloride is added as a precipitant in proportion (the amount of calcium chloride added is 10% of the total mass of the solution after addition), and the mixture is stirred at 300-500 rpm for 0.5 h at room temperature and then filtered to obtain a harmless liquid and filter residue.

[0054] S500: The pH value of the harmless liquid is adjusted to be the same as that of the biological modification solution, and then the harmless liquid is returned to the storage tank of the biological modification solution at a ratio of 30% of the total mass of the liquid in the storage tank for reuse, and the filter residue is further used to recover phosphorus, fluorine and heavy metals therein.

[0055] The harmless phosphogypsum obtained in step S300, the liquid obtained by solid-liquid separation in steps S200 and S300, and the finally obtained harmless liquid were subjected to toxicity leaching experiments respectively, and the phosphorus, fluorine and pH in the harmless liquid were measured. The results are shown in Table 2.

[0056] Table 2 Toxicity leaching test results

[0057] From Table 2, we can see that: 1) The pH value of the toxic leaching liquid of harmless phosphogypsum is 7.87, which is weakly alkaline, indicating that the harmless phosphogypsum has little effect on the acidity and alkalinity of the water body during the leaching process. The pH value of the liquid is 8.90, which is weakly alkaline, which may be due to the alkaline substances produced during the biological modification process. The pH value of the harmless liquid is 6.83, which is close to neutral, indicating that after precipitation treatment, the acidity and alkalinity of the liquid tends to be stable and meets environmental protection requirements.

[0058] 2) The phosphorus content in the non-hazardous phosphogypsum toxic leaching liquid is 0.472 mg / L, far lower than the phosphorus content of 129.000 mg / L in the toxic leaching liquid of the original phosphogypsum, indicating that the non-hazardous treatment effectively reduces the phosphorus leaching amount. The phosphorus content in the liquid is 14.560 mg / L, indicating that during the biological modification process, phosphorus is dissolved and released into the solution. The phosphorus content in the non-hazardous liquid is 0.008 mg / L. After precipitation treatment, the phosphorus content is significantly reduced and almost undetectable, indicating that the precipitant has a very good removal effect on phosphorus.

[0059] 3) The fluorine content in the non-hazardous phosphogypsum toxic leaching liquid is 1.14 mg / L, far lower than the fluorine content of 8.13 mg / L in the toxic leaching liquid of the original phosphogypsum, indicating that the non-hazardous treatment effectively reduces the fluorine leaching amount. The fluorine content in the liquid is 11.67 mg / L, indicating that during the biological modification process, fluorine is dissolved and released into the solution. The fluorine content in the non-hazardous liquid is 5.70 mg / L. Although the fluorine content is significantly reduced after the liquid is subjected to precipitation treatment, it is still higher than that of the non-hazardous phosphogypsum toxic leaching liquid, which may be due to the limited removal efficiency of the precipitant for fluorine.

[0060] In summary, the non-hazardous treatment in Example 2 is also effective in reducing the phosphorus and fluorine contents in the phosphogypsum toxic leaching liquid, and the pH value of the treated liquid is close to neutral, meeting the requirements of GB 8978-1996. Compared with Example 1, Example 2 is more significant in the removal effect of phosphorus, but slightly inferior in the removal effect of fluorine.

[0061] Control Example The toxicity leaching experiment was carried out on the original phosphogypsum according to the standard, and the values of phosphorus, fluorine and pH in it are shown in Table 3.

[0062] Table 3 Results of Phosphogypsum Leaching Experiment

[0063] The metal ion contents in the toxic leaching liquids of the phosphogypsums obtained after the non-hazardous treatments of Example 1 and Example 2 and the original phosphogypsum were detected, and the results are shown in Table 4.

[0064] Table 4 Heavy Metal Leaching Experiment Results of Examples and Original Phosphogypsum

[0065] As can be seen from Table 3, the pH value of the original phosphogypsum toxic leaching liquid is 2.27, showing strong acidity. The phosphorus content in the toxic leaching liquid is 129.000 mg / L, with a very high content, indicating that the original phosphogypsum contains a large amount of soluble phosphorus, which has a significant impact on water eutrophication. The fluorine content in the toxic leaching liquid is 8.13 mg / L, with a relatively high content, indicating that the original phosphogypsum contains a large amount of soluble fluorine, causing serious pollution to water bodies and soil. The phosphorus and fluorine contents in the toxic leaching liquid of the original phosphogypsum are extremely high and show strong acidity, posing a serious hazard to the environment.

[0066] As can be seen from Table 4, after the original phosphogypsum is treated harmlessly, the contents of various harmful metal ions in the phosphogypsum are significantly reduced or even completely removed. This indicates that the harmless treatment method has a significant effect in removing heavy metals and can effectively reduce the environmental pollution risk of phosphogypsum.

[0067] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art, within the technical scope disclosed by the present invention, can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A green, environmentally friendly and harmless coordinated treatment method for phosphogypsum, characterized in that: It includes slurry preparation, recycling modification, solid output, precipitation treatment, and liquid disposal steps, and the specific contents are: A. Slurry preparation: transporting phosphogypsum and bio-modified solution to a reaction device in proportion and stirring to react to prepare a mixed slurry; B. Circulation modification: the mixed slurry in the reaction device is separated into solid and liquid, and the liquid is filtered and discharged from the bottom of the reaction device; then the biological modification solution is added to the reaction device at least once, and the biological modification treatment operation of solid-liquid separation is performed after stirring the reaction according to step A; C. Outputting solids: After the predetermined biological modification treatment operation is completed in step B, the solids obtained by solid-liquid separation are taken out to obtain harmless phosphogypsum; D. Precipitation treatment: The liquid obtained by solid-liquid separation in steps B and C is transported to a liquid harmless device, a precipitant is added in proportion, and a harmless liquid is obtained after stirring and reacting; E. Liquid disposal: Discharge the harmless liquid directly or return it to the bio-modification solution storage tank for reuse.

2. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to claim 1 is characterized in that: In the step A, the ratio of the bio-modification solution is: 5 g / L soy peptone, 15 g / L casein peptone, 5 g / L sodium chloride, 60-90 g / L urea, and Bacillus pasteurianus liquid with an OD600 value of 1-2; the solid-liquid mass ratio of the phosphogypsum to the bio-modification solution is (2-1):

1.

3. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to claim 2 is characterized in that: In the step A, the biological modification solution is obtained by activating Bacillus pasteurianus and then inoculating 1V% Bacillus pasteurianus in a liquid culture medium containing 5g / L soy peptone, 15g / L casein peptone, 5g / L sodium chloride, and 60-90g / L urea for cultivation to obtain a Bacillus pasteurianus bacterial solution with an OD600 value of 1-2.

4. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to claim 2 is characterized in that: In the step A, the phosphogypsum and the bio-modified solution are stirred in a reaction device at 30° C. and pH 7 to 8 at 300 to 500 rpm for 20 to 24 hours.

5. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to claim 1 is characterized in that: In the step B, the biological modification treatment operation is cycled 1 to 3 times.

6. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to claim 1 is characterized by: In the steps B and C, the solid and liquid are separated until no more liquid flows out from the bottom of the suction filtration mechanism at the bottom of the reaction device.

7. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to any one of claims 1 to 6, characterized in that: In the step D, the precipitant is calcium chloride, and the amount of calcium chloride added is 8-10% of the total mass of the solution after addition.

8. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to claim 7 is characterized by: The liquid obtained by separating the calcium chloride from the solid and liquid is stirred in a liquid harmless device at room temperature and 300-500 rpm for reaction for 0.5-2 hours.

9. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to claim 8, characterized in that: The liquid obtained by solid-liquid separation is stirred and reacted with the calcium chloride, and then filtered to obtain a harmless liquid and a filter residue, and phosphorus, fluorine and heavy metals in the filter residue are further recovered.

10. The green, environmentally friendly and harmless coordinated treatment method of phosphogypsum according to any one of claims 1 to 6, characterized in that: In the step E, the harmless liquid is returned to the bio-modified solution storage tank for reuse, that is, the harmless liquid is returned to the bio-modified solution storage tank at a ratio of 30-50% of the total mass of the liquid in the storage tank, and the pH value of the harmless liquid is adjusted to be the same as the pH value of the bio-modified solution before returning.

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