Method for recovering chromium by reducing chromium-containing tailing leacheate based on microorganisms

Abstract

The invention provides a method for recovering chromium by reducing chromium-containing tailing leacheate based on microorganisms, hexavalent chromium is reduced into trivalent chromium at normal temperature by using a specific mixed flora, the consumption of chemical agents is remarkably reduced, and green treatment is realized. The reduced trivalent chromium is efficiently adsorbed by cation exchange resin, so that chromium resource recovery is realized, impurity anions such as silicon, aluminum and the like are effectively separated by utilizing cation characteristics of the trivalent chromium, and the recovery purity is further improved by pre-adjusting the pH value. The whole process highly integrates reduction and recovery links, overcomes the problems of long flow and more impurity introduction in the traditional method, can flexibly adjust the strain proportion according to the water quality of the leacheate to optimize the efficiency, and shows the obvious advantages of short flow, low cost and resource utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment and resource recycling, in particular to a method for recovering chromium based on microbial reduction of chromium-containing tailing leaching solution. BACKGROUND

[0002] After washing the tailings in the production process of chromium salt, a large amount of tailing leaching solution containing hexavalent chromium is produced, which must be disposed of before further use. At present, the methods for removing hexavalent chromium from wastewater mainly include reduction precipitation method and adsorption method.

[0003] However, the conventional reduction precipitation method has problems such as complex process, large land occupation, large consumption of reagents, and limited use scenarios; for the adsorption method, the cost is relatively high, and chromium is mainly recovered in the form of hexavalent chromium, and the toxicity cannot be effectively reduced. Therefore, it is urgent to propose a new chromium-containing tailing leaching solution short process treatment method which can effectively recover chromium resources to solve the problems of long treatment process, large consumption of reagents, and non-reduction of toxicity of the existing methods. SUMMARY

[0004] To solve the above problems, the present application provides a method for recovering chromium based on microbial reduction of chromium-containing tailing leaching solution, which reduces the consumption of chemical reagents by reducing hexavalent chromium to trivalent chromium at room temperature, and realizes green disposal. The trivalent chromium after reduction is adsorbed by cation exchange resin, not only realizing the recovery of chromium resources, but also effectively separating impurity anions such as silicon and aluminum by using its cationic characteristics, and further improving the recovery purity by pre-adjusting the pH. The whole process integrates reduction and recovery links, overcomes the problems of long process and introduction of impurities in traditional methods, and can flexibly adjust the proportion of strains to optimize efficiency according to the water quality of leaching solution, showing significant advantages of short process, low cost and resource utilization.

[0005] In the first aspect, the present application provides a method for recovering chromium based on microbial reduction of chromium-containing tailing leaching solution, which comprises: adjusting the pH of the chromium-containing tailing leaching solution to 6-9, and obtaining a filtrate after filtration; mixing the filtrate with freeze-dried reduction bacteria powder, and performing microbial reduction reaction at 25-35 DEG C to reduce hexavalent chromium in the filtrate to trivalent chromium; passing the filtrate after the microbial reduction reaction through an ion exchange column filled with cation exchange resin, so that the cation exchange resin adsorbs the trivalent chromium; after desorption treatment of the cation exchange resin adsorbed with the trivalent chromium, the recovery of chromium is completed; wherein the reduction bacteria are selected from at least two of Bacillus megaterium, Pseudomonas putida, Stenotrophomonas and Ochrobactrum.

[0006] Optionally, the mass-volume ratio of the freeze-dried reducing bacteria powder to the chromium-containing tailings leaching solution is 0.5 g:1 L-1 g:1 L.

[0007] Optionally, the cation exchange resin is a macroporous cation exchange resin and / or a chelating cation exchange resin.

[0008] Optionally, the flow rate of the filtrate after the microbial reduction reaction through the ion exchange column is 1.0 BV / h-20.0 BV / h.

[0009] Optionally, the method for obtaining the freeze-dried reducing bacteria powder comprises: Inoculating at least two of the Bacillus megaterium, the Pseudomonas putida, the Stenotrophomonas and the Ochrobactrum into a liquid alkaline medium containing hexavalent chromium, respectively, and culturing at a temperature of 30-35°C for 7 days; Then, inoculating at a 10% v / v inoculation amount and continuing to domesticate the microorganisms for 2-4 cycles with a cycle of 7 days; After domestication, inoculating at a 10% v / v inoculation amount for expansion culture, using a freeze dryer to prepare a freeze-dried powder from the bacterial liquid obtained after the expansion culture, and mixing at least two freeze-dried powders to obtain the freeze-dried reducing bacteria powder.

[0010] Optionally, the reducing bacteria in the freeze-dried reducing bacteria powder are composed of the Stenotrophomonas, the Bacillus megaterium, the Pseudomonas putida and the Ochrobactrum. The mass ratio of the Stenotrophomonas freeze-dried reducing bacteria powder, the Bacillus megaterium freeze-dried reducing bacteria powder, the Pseudomonas putida freeze-dried reducing bacteria powder and the Ochrobactrum freeze-dried reducing bacteria powder is 2:1:1:1.

[0011] Optionally, the liquid alkaline medium comprises tryptone, yeast extract, potassium dichromate and sodium chloride. The addition amount of the tryptone, the yeast extract, the potassium dichromate and the sodium chloride is 8-12 g / L, 4-6 g / L, 0.1-0.5 g / L and 4-6 g / L, respectively.

[0012] Optionally, the chromium concentration in the chromium-containing tailings leaching solution is not more than 1 g / L.

[0013] Optionally, the method further comprises; Collecting the reducing bacteria in the remaining filtrate after the microbial reduction reaction after filtering through the ion exchange column.

[0014] Optionally, the pore size of the filter membrane for filtering the remaining filtrate after the microbial reduction reaction is 0.1-0.45 μm.

[0015] Beneficial technical effects: The application provides a method for recovering chromium based on microbial reduction of chromium-containing tailings leaching solution, integrates the reduction of hexavalent chromium and the chromium recovery link, continuously recovers chromium while completing the reduction of chromium, effectively avoids the problem of long processing flow caused by the separation of the treatment and recovery links in the existing treatment process, and has a significant short-flow advantage. The application uses microorganisms (at least two of bacillus megaterium, pseudomonas putida, stenotrophomonas and ochrobactrum) to reduce chromium, can effectively reduce the consumption of reagents in the treatment process of hexavalent chromium-containing wastewater, reduce the introduction amount of impurity heavy metal ions in the treatment process, and realize green disposal of the chromium-containing tailings leaching solution. The application realizes effective separation of chromium and impurity anions by reducing chromium to trivalent cations and adsorbing the trivalent cations on the cation exchange resin, can solve the problem that chromium is difficult to separate from impurities such as silicon and aluminum when chromium is adsorbed in the form of anions in the existing process, and can further improve the effect of selective recovery of chromium by pre-adjusting the pH to partially remove impurity cations in the chromium-containing tailings leaching solution. The application can flexibly adjust the proportion of the main species in the chromium-reducing bacteria according to the reduction effect of the microorganisms on hexavalent chromium in different chromium-containing tailings leaching solutions, thereby effectively improving the reduction efficiency of hexavalent chromium. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without any creative labor.

[0017] Figure 1 A flow chart of the method for recovering chromium based on microbial reduction of chromium-containing tailings leaching solution provided by the embodiments of the present application is shown. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, anyone can obtain any product same or similar to the present application under the inspiration of the present application or by combining the present application with other existing technical features, which falls within the protection scope of the present application. In addition, all other embodiments obtained by those skilled in the art without any creative labor are within the protection scope of the present application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The materials, methods, and examples provided herein are illustrative only and not intended to be limiting. Except in the Examples, or where otherwise explicitly indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, suitable methods and materials are described below. All publications mentioned herein are incorporated by reference in their entirety to disclose and provide

[0020] Techniques, methods, and apparatus known to the skilled artisan can not be discussed in detail herein. However, where appropriate, such techniques, methods, and apparatus should be considered as falling within the scope of the present application.

[0021] In the description of the present application, it needs to be understood that the use of the words such as "first", "second", and the like to qualify elements is merely intended to facilitate a distinction as to corresponding elements and does not have a special meaning unless otherwise stated, and therefore should not be understood as limiting the scope of protection of the present application.

[0022] In addition, the technical features involved in the different embodiments of the application described below can be combined with each other as long as they do not conflict with each other.

[0023] In the related art, after the tailings in the production process of chromium salt are washed, a large amount of tailings leaching solution containing hexavalent chromium is generated, which must be disposed to be further utilized. At present, the methods for removing hexavalent chromium in wastewater mainly include reduction precipitation method and adsorption method. However, the conventional reduction precipitation method has problems such as complex process, large land occupation, large consumption of reagents, and the like, and the use scene is limited; for the adsorption method, the cost is relatively high, and chromium is mainly recovered in the form of hexavalent chromium, and the toxicity cannot be effectively reduced.

[0024] For example, CN120364830A discloses a method for treating chromium wastewater by modified biochar infiltration column combined with microorganisms, a composite filler layer is constructed by loading hydroxyapatite on straw biochar through alkali modification, and a synergistic system is formed with the selected Bacillus cereus FZUY-01, so as to realize chemical fixation of trivalent chromium; but the preparation process of the filler used in the method is relatively complex, and effective recovery of trivalent chromium cannot be realized; CN120463885A discloses a phenolic resin polymer ball and a preparation method thereof, the provided phenolic resin polymer ball can significantly improve the adsorption capacity and adsorption efficiency of chromium, and shorten the treatment process of chromium-containing wastewater; but the method still needs to add chemical reagents to reduce hexavalent chromium in wastewater, and the consumption of reagents is large; CN120117790A discloses a chromium-containing wastewater treatment device, which utilizes a photoreduction reaction to treat hexavalent chromium ions in wastewater, shortens the treatment period of wastewater containing hexavalent chromium ions, and is relatively convenient to operate; however, the method needs to prepare a photoreduction agent, the treatment effect of the device is subject to the performance of the reduction agent, and the treated trivalent chromium cannot be recovered.

[0025] Under the overall trend of increasingly strict green and environmental protection production requirements, microbial treatment technology has become an important development direction of chromium-containing wastewater treatment and resource recycling industry. Based on this, the embodiment of the present application provides a method for recovering chromium from chromium-containing tailing leaching solution based on microbial reduction, which can realize detoxification and disposal of hexavalent chromium at the same time compared with conventional methods, and has obvious process advantages.

[0026] Figure 1 The flow chart of the method for recovering chromium from chromium-containing tailing leaching solution based on microbial reduction provided by the embodiment of the present application is shown as follows, Figure 1 The method specifically includes the following steps: Step S1: adjusting the pH of the chromium-containing tailing leaching solution to 6-9 to obtain a filtrate after filtration; It should be noted that the chromium-containing tailing leaching solution is wastewater containing highly toxic hexavalent chromium obtained after washing the hexavalent chromium-containing tailings generated in the production process of chromium salt; In some embodiments, the chromium concentration in the chromium-containing tailing leaching solution is not more than 1g / L; In the chromium-containing tailing leaching solution with a chromium concentration of not more than 1g / L, the mixed bacteria population with specific domestication can efficiently and stably reduce hexavalent chromium within its tolerance and metabolic capacity range in the embodiment of the present application.

[0027] In some embodiments, the reagent for adjusting the pH of the chromium-containing tailing leaching solution is concentrated sulfuric acid or calcium hydroxide; by pre-adjusting the pH of the chromium-containing tailing leaching solution, the present embodiment can partially remove impurity cations in the chromium-containing tailing leaching solution, which helps to further improve the effect of selective chromium recovery; Step S2: mixing the filtrate with freeze-dried reduction bacteria powder and performing a microbial reduction reaction at 25-35℃ to reduce hexavalent chromium in the filtrate to trivalent chromium; It should be noted that the reduction bacteria are selected from at least two of Bacillus megaterium, Pseudomonas putida, Stenotrophomonas and Ochrobactrum anthropi; the present application utilizes the synergistic effect between bacteria to enhance the adaptability to different environmental conditions, improve the efficiency and stability of the hexavalent chromium reduction reaction, so as to more reliably achieve the goal of toxicity reduction and chromium recovery on the basis of simplifying the process and reducing the use of reagents; In some embodiments, the method for obtaining the freeze-dried reduction bacteria powder includes: Inoculate at least two of the Bacillus megaterium, the Pseudomonas putida, the Stenotrophomonas sp and the Ochrobactrum anthropi respectively into the alkaline liquid medium containing hexavalent chromium, and culture at a temperature of 30-35 DEG C for 7 days; Inoculate at the amount of 10% v / v again and continue to domesticate the microorganisms for 2-4 cycles with a cycle of 7 days; Inoculate the domesticated strains at the amount of 10% v / v for expansion culture, freeze dry the bacterial liquid obtained after the expansion culture to prepare freeze-dried powder, mix at least two freeze-dried powders to prepare the freeze-dried reducing bacteria powder.

[0028] In some embodiments, the alkaline liquid medium comprises tryptone, yeast extract, potassium dichromate and sodium chloride; The addition amounts of the tryptone, the yeast extract, the potassium dichromate and the sodium chloride are 8-12 g / L, 4-6 g / L, 0.1-0.5 g / L and 4-6 g / L respectively; The addition amount of the tryptone is 8 g / L, 9 g / L, 10 g / L, 11 g / L or 12 g / L; The addition amount of the yeast extract is 4 g / L, 4.5 g / L, 5 g / L, 5.5 g / L or 6 g / L; The addition amount of the potassium dichromate is 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L or 0.5 g / L; The addition amount of the sodium chloride is 4 g / L, 4.5 g / L, 5 g / L, 5.5 g / L or 6 g / L; In the embodiments of the present application, the tryptone and the yeast extract in the alkaline liquid medium provide sufficient nutrients for the growth of the microorganisms, and the specific low concentration range of the potassium dichromate serves as the domestication pressure, so that the strains can grow stably while obtaining high reducing activity; It should be noted that, for example, at least two of the Bacillus megaterium, the Pseudomonas putida, the Stenotrophomonas sp and the Ochrobactrum anthropi are inoculated into the alkaline liquid medium containing hexavalent chromium, and cultured at a temperature of 30 DEG C, 31 DEG C, 32 DEG C, 33 DEG C, 34 DEG C or 35 DEG C; The freeze-dried powder is prepared by freeze-drying the bacterial liquid into a dry powder, which can maintain the activity and stability of the strains for a long time, greatly facilitating the storage, transportation and ready access of the microbial agent; In the embodiments of the present application, the specific strains are induced by using the alkaline medium containing hexavalent chromium in the pre-sequence domestication stage for multiple cycles, and finally prepared into freeze-dried powder, so that the obtained microbial agent has strong tolerance and high reducing activity to the target leaching liquid environment, thereby ensuring the efficiency and stability of the microbial reduction reaction and realizing the unification of the simplification of the treatment process and the operation reliability.

[0029] It should be further noted that before use, the bacterial liquid of the above at least two bacteria can be inoculated into the filtrate of the chromium tailings leaching solution adjusted in pH and filtered at an inoculation amount of 10% v / v, and cultured at 30℃ for 3 days, the reduction effect of the four bacteria on hexavalent chromium in the filtrate is investigated, and the best bacteria is selected as the main bacteria.

[0030] In some embodiments, the oligotrophic bacteria have the best reduction effect on hexavalent chromium in the filtrate; In some embodiments, the reduction bacteria in the freeze-dried reduction bacteria powder are composed of the oligotrophic bacteria, the bacillus megaterium, the pseudomonas putida and the xanthobacter; The mass ratio of the oligotrophic bacteria freeze-dried reduction bacteria powder, the bacillus megaterium freeze-dried reduction bacteria powder, the pseudomonas putida freeze-dried reduction bacteria powder and the xanthobacter freeze-dried reduction bacteria powder is 2:1:1:1. In some embodiments, the mass-volume ratio of the freeze-dried reduction bacteria powder to the chromium tailings leaching solution is 0.5g:1L-1g:1L.

[0031] It should be noted that, for example, the mass-volume ratio of the freeze-dried reduction bacteria powder to the chromium tailings leaching solution is 0.5g:1L, 0.6g:1L, 0.7g:1L, 0.8g:1L, 0.9g:1L, 1g:1L; by setting the mass-volume ratio of the freeze-dried reduction bacteria powder to the chromium tailings leaching solution in the range of 0.5g:1L-1g:1L, the present embodiment ensures that the high-activity bacteria powder cultured can quickly start and efficiently complete the reduction reaction of hexavalent chromium, optimizes the processing cost, and avoids the efficiency problem caused by the waste of bacteria or insufficient amount.

[0032] It should be further noted that the temperature of the microbial reduction reaction is 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃; in the present embodiment, the temperature of the microbial reduction reaction is in the range of 25℃-35℃, which provides the most suitable and easy-to-maintain metabolic activity conditions for the domesticated high-efficiency mixed bacteria, without the need for additional energy consumption for heating or cooling, further reducing the operating cost and operation complexity, and strengthening the practicality and economy of the method.

[0033] Step S3: passing the filtrate after the microbial reduction reaction through an ion exchange column filled with cation exchange resin, so that the cation exchange resin adsorbs the trivalent chromium; after desorption treatment of the cation exchange resin adsorbed with the trivalent chromium, the recovery of chromium is completed; In some embodiments, the cation exchange resin is a macroporous cation exchange resin and / or a chelating cation exchange resin. By using a macroporous cation exchange resin and / or a chelating cation exchange resin, the embodiments of the present application take advantage of the high mechanical strength, large specific surface area, and high selectivity and adsorption capacity for trivalent chromium ions, to ensure that the trivalent chromium generated by microbial reduction can be efficiently and stably adsorbed and enriched.

[0034] It should be noted that the amount of cation exchange resin can be determined according to the total amount of the filtrate after the microbial reduction reaction and the concentration of trivalent chromium therein.

[0035] In some embodiments, the flow rate of the filtrate after the microbial reduction reaction through the ion exchange column is 1.0 BV / h-20.0 BV / h.

[0036] For example, the flow rate of the filtrate after the microbial reduction reaction through the ion exchange column is 1.0 BV / h, 2 BV / h, 4 BV / h, 5 BV / h, 8 BV / h, 10 BV / h, 12 BV / h, 14 BV / h, 16 BV / h, 18 BV / h, or 20.0 BV / h. By setting the operating flow rate of the ion exchange column in the range of 1.0 BV / h-20.0 BV / h, the embodiments of the present application ensure that the trivalent chromium ions in the filtrate after microbial reduction have sufficient contact time with the cation exchange resin to achieve efficient adsorption, while also taking into account the processing efficiency, optimizing the operating efficiency and stability of the overall process under the premise of high recovery rate of chromium resources.

[0037] It should be noted that in step S3, the filtrate after the microbial reduction reaction is passed through the ion exchange column filled with cation exchange resin, so that the trivalent chromium in the filtrate after the microbial reduction reaction is continuously adsorbed. When the total chromium content in the filtrate is reduced to below 1 mg / L, the flow of the filtrate into the ion exchange column is stopped.

[0038] In summary, the embodiment of the present application provides a short process solution for the resource treatment of the leaching solution of chromium-containing tailings by constructing a synergistic treatment system combining microbial reduction and ion exchange resin adsorption. First, the pH value of the leaching solution of chromium-containing tailings is regulated, and then the mixed bacteria group (such as Bacillus megaterium, Pseudomonas putida, etc.) which is domesticated for multiple cycles by a specific chromium-containing alkaline medium and is preserved in the form of freeze-dried bacteria powder is used to efficiently reduce the high-toxicity hexavalent chromium to low-toxicity trivalent chromium at an optimized bacteria powder dosage ratio (0.5-1 g / L) under normal temperature conditions of 25-35 DEG C, thereby fundamentally realizing effective reduction of toxicity. Subsequently, the filtrate is guided to an ion exchange column filled with macroporous cation exchange resin or chelating cation exchange resin, and under an optimized flow rate of 1.0-20.0 BV / h, the trivalent chromium ions are selectively adsorbed and enriched, thereby realizing efficient recovery of chromium resources. The whole process is closely linked, the pre-domestication of the bacteria agent guarantees the reduction efficiency, the selection of the ion exchange resin and the optimization of the operation parameters guarantee the recovery rate, and the terminal bacteria collection step (using 0.1-0.45 μm microfiltration) ensures the clarity of the effluent water quality and the stable operation of the system. The method provided by the embodiment of the present application completely avoids the inherent defects of the traditional reduction precipitation method such as large reagent consumption and large sludge production and the adsorption method such as high cost and non-reduction of toxicity, forms a clean treatment path which is free of complex equipment, easy to operate, has high resource recovery rate and is environmentally friendly, and significantly improves the sustainability level of hazardous waste treatment in the chromium salt industry.

[0039] In some embodiments, the method further comprises; filtering the remaining filtrate after the microbial reduction reaction, and collecting the reduction bacteria in the remaining filtrate after the microbial reduction reaction.

[0040] The embodiment of the present application realizes effective separation of the bacteria and the treated liquid by adding a collection step of the reduction bacteria in the remaining filtrate after passing through the ion exchange column, thereby avoiding potential influence of the bacteria residues on the effluent water quality or subsequent process steps.

[0041] In some embodiments, the pore size of the filter membrane for filtering the remaining filtrate after the microbial reduction reaction is 0.1-0.45 μm.

[0042] It should be noted that, for example, the pore size of the filter membrane for filtering the remaining filtrate after the microbial reduction reaction is mainly 0.1 μm, 0.22 μm, 0.45 μm or other available pore sizes within the range of 0.1-0.45 μm. The embodiment of the present application uses a filter membrane with a pore size of 0.1-0.45 μm to filter the remaining filtrate after ion exchange, which can efficiently and completely intercept and separate the microbial reduction bacteria, thereby ensuring the clarity of the final effluent water and effectively preventing potential interference of the bacteria residues on subsequent processes or discharge environment.

[0043] In order for those skilled in the art to more clearly understand the present application, the method for recovering chromium from chromium-containing tailing leaching solution based on microorganisms provided by the present application is described in detail through the following examples.

[0044] Example 1 This example disposes of 30L of chromium-containing tailing leaching solution from alkaline leaching of a chromium-iron ore in Gansu and recovers chromium, including the following steps: (1) The pH of the chromium-iron ore alkaline leaching tailing leaching solution is measured to be 11.6, and concentrated sulfuric acid is slowly added until the pH drops to 9.0, filtered, and the main element composition of the obtained filtrate is measured as shown in Table 1; Table 1. Main element composition of chromium-iron ore alkaline leaching tailing leaching solution

[0045] (2) Four 100ml filtrates are taken, and four bacteria species with chromium reduction capacity, i.e., Bacillus megaterium, Pseudomonas putida, Stenotrophomonas and Xanthobacter, are inoculated into the filtrates at an addition amount of 10% v / v, respectively. After 3 days of culture at 30°C, the content of hexavalent chromium in the four filtrates is measured and the hexavalent chromium removal rate is calculated, and the results are shown in Table 2. It can be seen that Stenotrophomonas has better hexavalent chromium removal effect among the four bacteria; Table 2. Reduction effect of four bacteria on hexavalent chromium

[0046] (3) The four bacteria are expanded and cultured, respectively, and the bacterial liquid is inoculated into an alkaline liquid medium containing hexavalent chromium at a concentration of 100mg / L and pH 9, and cultured at 30°C for 7 days. After the end, the inoculation is transferred at an inoculation amount of 10% v / v, and the microorganisms are domesticated for 4 cycles with a period of 7 days. After domestication, the bacteria are expanded and cultured at 30°C in an alkaline liquid medium with pH 9 at an inoculation amount of 10% v / v, to obtain expanded bacterial liquid, and freeze-dried to form freeze-dried powder. The freeze-dried powders of the four bacteria are mixed to form freeze-dried reduction bacteria powder; (4) According to the amount of chromium-iron ore alkaline leaching tailing leaching solution, inoculation is carried out at a total inoculation amount of 0.8g / L, i.e., a total of 24g of freeze-dried reduction bacteria powder is inoculated, wherein the amount of Stenotrophomonas freeze-dried reduction bacteria powder is 9.6g, and the amounts of Bacillus megaterium freeze-dried reduction bacteria powder, Pseudomonas putida freeze-dried reduction bacteria powder and Xanthobacter freeze-dried reduction bacteria powder are 4.8g, respectively; (5) The freeze-dried reduced bacteria powder is added to the filtrate, and the filtrate is circulated and adsorbed through an ion exchange column filled with 100 mL of CH-90 chelated ion exchange resin at a flow rate of 5.0 BV / h. The change of the total chromium concentration in the solution with the adsorption time is shown in Table 3. After the CH-90 chelated ion exchange resin is circulated and adsorbed for 120 h, the total chromium concentration in the filtrate is reduced to 0.48 mg / L. The filtrate is filtered through a microporous filter membrane with a pore size of 0.3 μm to obtain a secondary filtrate. The CH-90 chelated ion exchange resin loaded with trivalent chromium is desorbed to obtain a chromium-containing solution for further recovery of chromium.

[0047] Table 3. Change of total chromium concentration with time in the adsorption process of CH-90 chelated ion exchange resin

[0048] According to Table 3, it can be seen that as the adsorption time is prolonged from 12 h to 120 h, the total chromium concentration in the solution is continuously and significantly reduced from the initial 171.56 mg / L to 0.48 mg / L. This result proves that the ion exchange step can efficiently and thoroughly remove chromium in the solution. The adsorption process has a faster rate in the early stage (0-72 h) and a slower rate in the later stage. The final chromium concentration in the effluent is very low, which meets the dual goals of efficient recovery and deep purification, and verifies the feasibility and effectiveness of the ion exchange process for chromium resource recovery in the embodiment of the present application.

[0049] Example 2 Example 2 is different from Example 1 only in that the filtrate is circulated and adsorbed through a resin column filled with 100 mL of T-52 chelated ion exchange resin at a flow rate of 5.0 BV / h. The change of the total chromium concentration in the solution with the adsorption time is shown in Table 4. After the T-52 chelated ion exchange resin is circulated and adsorbed for 102 h, the total chromium concentration in the filtrate is reduced to 0.53 mg / L. The filtrate is filtered through a microporous filter membrane with a pore size of 0.45 μm to obtain a secondary filtrate. The T-52 chelated ion exchange resin loaded with trivalent chromium is desorbed with 10% sulfuric acid to obtain a chromium-containing solution for further recovery of chromium.

[0050] Table 4. Change of total chromium concentration with time in the adsorption process of T-52 chelated ion exchange resin

[0051] According to Table 4, it can be obtained that with the adsorption time being prolonged from 12h to 102h, the chromium concentration continuously and significantly decreases from 171.56 mg / L to 0.53 mg / L. This result verifies that the T-52 chelate type ion exchange resin has the ability of efficiently and deeply removing chromium, and the adsorption kinetics characteristics are similar to those of the CH-90 chelate type ion exchange resin, both of which show that the adsorption rate is fast in the early stage and tends to be balanced in the later stage. It is further verified that the reliability and effectiveness of the ion exchange process for realizing chromium resource recovery in the embodiment of the application, which indicates that different types of suitable resins can achieve excellent chromium recovery effect.

[0052] In summary, the embodiment of the application provides a method for recovering chromium based on microbial reduction of chromium-containing tailings leaching solution, which integrates the reduction of hexavalent chromium and the chromium recovery link, and continuously recovers chromium while completing the reduction of chromium, which can effectively avoid the problem of long processing flow caused by the separation of the treatment and recovery links in the existing treatment process, and has a significant short flow advantage; The embodiment of the application can effectively reduce the consumption of reagents in the treatment process of the wastewater containing hexavalent chromium, reduce the introduction amount of impurity heavy metal ions in the treatment process, and realize green disposal of the chromium-containing tailings leaching solution by using microorganisms (at least two of Bacillus megaterium, Pseudomonas putida, Stenotrophomonas and Bacteroides) to reduce chromium. The embodiment of the application can effectively separate chromium from impurity anions by reducing chromium to trivalent cations and being adsorbed by resins, which can solve the problem that chromium is difficult to separate from impurities such as silicon and aluminum when adsorbed in the form of anions in the existing process, and the impurity cations in the chromium-containing tailings leaching solution can be partially removed by pre-adjusting the pH, which can further improve the selective recovery effect of chromium. The embodiment of the application can flexibly adjust the proportion of the main strain composition in the chromium reduction bacteria according to the reduction effect of the microorganisms on the hexavalent chromium in the different chromium-containing tailings leaching solution, thereby effectively improving the reduction efficiency of hexavalent chromium.

[0053] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same and similar parts of each embodiment can be referred to each other.

[0054] Although the preferred embodiments of the application have been described, those skilled in the art can make other changes and modifications to the embodiments once they know the basic creative concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the application.

[0055] Finally, it is to be understood that the phraseology or terminology such as "first" and "second" etc. used herein is merely intended to differentiate one entity or operation from another without necessarily requiring or implying any actual such relationship or order between such entities or operations. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0056] The above describes in detail the method for recovering chromium from the leaching solution of chromium-containing tailings by microorganism reduction provided by the present application. The principles and implementation manners of the present application are described by using specific examples. The above description of the examples is only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A method for recovering chromium from a leachate of chromium-containing tailings based on microbial reduction, characterized by, The method comprises: adjusting the pH of the chromium-containing tailings leachate to 6-9, and obtaining a filtrate after filtration; mixing the filtrate with freeze-dried reducing bacteria powder, and performing a microbial reduction reaction at 25-35 DEG C to reduce hexavalent chromium in the filtrate to trivalent chromium; passing the filtrate after the microbial reduction reaction through an ion exchange column filled with cation exchange resin, allowing the cation exchange resin to adsorb the trivalent chromium, and performing desorption treatment on the cation exchange resin adsorbed with the trivalent chromium to complete chromium recovery; wherein the reducing bacteria are selected from at least two of Bacillus megaterium, Pseudomonas putida, Stenotrophomonas and Ochrobactrum.

2. The method for recovering chromium from a chromium-containing tailings leaching solution based on microorganisms according to claim 1, characterized in that, The mass-volume ratio of the freeze-dried reducing bacteria powder to the chromium-containing tailings leachate is 0.5 g:1 L-1 g:1 L.

3. The method for recovering chromium from a chromium-containing tailings leaching solution based on microorganisms according to claim 1, characterized in that, The cation exchange resin is a macroporous cation exchange resin and / or a chelating cation exchange resin.

4. The method for recovering chromium from a chromium-containing tailings leaching solution based on microorganisms according to claim 1, characterized in that, The flow rate of the filtrate after the microbial reduction reaction through the ion exchange column is 1.0 BV / h-20.0 BV / h.

5. The method for recovering chromium from a chromium-containing tailings leaching solution based on microorganisms according to claim 1, characterized in that, The method for obtaining the freeze-dried reducing bacteria powder comprises: Inoculating at least two of the Bacillus megaterium, Pseudomonas putida, Stenotrophomonas and Ochrobactrum into a basic liquid medium containing hexavalent chromium, and culturing at 30-35 DEG C for 7 days; Transferring at an inoculation amount of 10% v / v and continuing to domesticate the microorganisms for 2-4 cycles with a cycle of 7 days; Inoculating the domesticated strains at an inoculation amount of 10% v / v, expanding the culture, using a freeze dryer to prepare a freeze-dried powder from the bacterial liquid obtained after the expansion culture, and mixing at least two freeze-dried powders to obtain the freeze-dried reducing bacteria powder.

6. The method for recovering chromium from a chromium-containing tailings leachate based on microorganisms according to claim 5, characterized in that, The reducing bacteria in the freeze-dried reducing bacteria powder are composed of the Stenotrophomonas, the Bacillus megaterium, the Pseudomonas putida and the Ochrobactrum; The mass ratio of the Stenotrophomonas freeze-dried reducing bacteria powder, the Bacillus megaterium freeze-dried reducing bacteria powder, the Pseudomonas putida freeze-dried reducing bacteria powder and the Ochrobactrum freeze-dried reducing bacteria powder is 2:1:1:

1.

7. The method for recovering chromium from a chromium-containing tailings leaching solution based on microorganisms according to claim 5, characterized in that, The basic liquid medium comprises tryptone, yeast extract, potassium dichromate and sodium chloride; The addition amounts of the tryptone, the yeast extract, the potassium dichromate and the sodium chloride are 8-12 g / L, 4-6 g / L, 0.1-0.5 g / L and 4-6 g / L, respectively.

8. The method for recovering chromium from a chromium-containing tailings leaching solution based on microorganisms according to claim 1, characterized in that, The chromium concentration in the chromium-containing tailings leachate is not more than 1 g / L.

9. The method for recovering chromium from a chromium-containing tailings leachate based on microorganisms according to any one of claims 1-8, characterized in that, The method further comprises; collecting the reducing bacteria in the remaining filtrate after the microbial reduction reaction.

10. The method for recovering chromium from a chromium-containing tailings leachate based on microorganisms according to claim 9, characterized in that, The pore size of the filter membrane for filtering the remaining filtrate after the microbial reduction reaction is 0.1-0.45 μm.

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