Method for recycling scandium element by using microbial electrolysis cell

Abstract

The invention relates to the technical field of bioelectrochemistry, and discloses a method for recycling scandium element by using a microbial electrolysis cell, the microbial electrolysis cell comprises an anode chamber and a cathode chamber, the anode chamber comprises a positive electrode, and the cathode chamber comprises a negative electrode; comprising the following steps that organic wastewater is injected into an anode chamber, and a positive electrode comprises a microorganism-enriched carbon-based material; injecting the scandium-containing waste liquid into the cathode chamber; external voltage is applied to the microbial electrolysis tank for electrolysis, and Sc (OH) 3 generated in the cathode chamber is collected after electrolysis is completed. According to the method, a microorganism-enriched carbon-based material is used as a positive electrode, electron donors in organic wastewater are utilized, electrons are transmitted to a negative electrode through an external circuit, hydrogen is generated at the negative electrode, meanwhile, a large amount of OH <-> is generated, Sc < 3 + > in the scandium-containing waste liquid is combined with OH <-> to generate Sc (OH) 3, and after solid-liquid separation, precipitates are heated to obtain Sc2O3; organic pollutants are effectively degraded, scandium in the rare earth ore wastewater is recycled, and resource utilization is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of bioelectrochemistry, and in particular to a method for recovering scandium by utilizing a microbial electrolytic cell. Background Art

[0002] Scandium (Sc), one of the most valuable rare earth elements, can not only be used as a dopant to reduce the weight of automobiles, aerospace industry equipment, electronic equipment, etc., but can also significantly improve the output performance of solid oxide fuel cells and reduce the operating temperature.

[0003] Scandium is generally associated with other minerals and rarely exists as an independent ore. A very small amount of scandium is extracted from primary resources, and most of it is extracted from secondary resources, such as from bauxite slag red mud, laterite nickel ore, titanium dioxide waste acid, etc. Scandium recovery and extraction technology has significant characteristics such as complex process, high cost, and great difficulty. In the existing technology, the main methods used to recover rare earth elements such as scandium include: first forming different types of pre-concentrates from ores containing rare earth elements, then dissolving them with strong acids (acid leaching process with a pH lower than 4), and finally extracting with organic solvents. The above-mentioned technology has the disadvantages of low scandium recovery rate, high acid consumption, and the leachate or contaminated water produced by acid leaching must be treated with separation technology, requiring multi-stage extraction, and the organic solvent is toxic, time-consuming and labor-intensive. In other words, the low recovery rate and high recovery cost of scandium limit its application in cutting-edge fields.

[0004] Therefore, how to adjust and optimize the scandium recovery method to achieve effective comprehensive utilization of recovered scandium resources is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a method for recovering scandium using a microbial electrolytic cell to solve the problem of low scandium recovery rate in the prior art.

[0006] In a first aspect, the present invention provides a method for recovering scandium using a microbial electrolysis cell, wherein the microbial electrolysis cell comprises an anode chamber and a cathode chamber, wherein the anode chamber comprises an anode electrode, and the cathode chamber comprises a cathode electrode; and the method comprises the following steps:

[0007] Injecting organic wastewater into the anode chamber, wherein the anode comprises a carbon-based material enriched with microorganisms; injecting scandium-containing wastewater into the cathode chamber;

[0008] An external voltage is applied to the microbial electrolysis cell to perform electrolysis, and after the electrolysis is completed, Sc(OH)3 generated in the cathode chamber is collected.

[0009] In an optional embodiment, the concentration of scandium ions in the scandium-containing waste liquid is 5 mg / L-200 mg / L.

[0010] In an optional embodiment, the electrolysis temperature is 20°C-40°C, and the time is 1h-24h.

[0011] In an optional embodiment, the applied external voltage is 1.0V-2.5V, and the external resistance is 1Ω-1000Ω.

[0012] In an optional embodiment, the chemical oxygen demand of the organic wastewater is 100 mg / L-2000 mg / L.

[0013] In an optional embodiment, after the electrolysis is completed, the Sc(OH)3 is obtained by centrifugation and drying steps; and the Sc(OH)3 is calcined to obtain Sc2O3.

[0014] In an optional embodiment, the centrifugation time is 10 min-30 min, and the rotation speed is 4000 rpm-10000 rpm.

[0015] In an optional embodiment, the drying temperature is 100° C.-110° C., and the drying time is 18 h-36 h.

[0016] In an optional embodiment, the calcination temperature is 500° C.-600° C., and the calcination time is 1 h-3 h.

[0017] In an optional embodiment, the carbon-based material includes at least one of a carbon brush, a carbon felt, a carbon rod, and a graphite felt.

[0018] In an optional embodiment, the cathode electrode of the microbial electrolysis cell includes a composite metal material; the composite metal material includes at least one of a stainless steel mesh, a titanium sheet, Pt / C, and a metal-organic framework material.

[0019] In an optional embodiment, the microbially enriched carbon-based material is prepared by the following steps: injecting the anolyte and electrochemically active microorganisms into the anode chamber, injecting the cathode liquid into the cathode chamber, and testing the voltage of the microbial electrolysis cell until the voltage is maintained at 300mV-600mV, indicating that the enrichment is complete.

[0020] In an optional embodiment, the raw material composition of the anolyte includes, per 1L of deionized water, KH2PO4 2.0g-2.5g, Na2HPO4 2.5g-3.0g, MgSO4·7H2O 0.3g-0.7g, NH4Cl0.8g-1.2g, NaHCO3 0.4g-0.6g, CaCl2·2H2O 0.01g-0.03g, ammonium ferric citrate 0.03g-0.06g, H3BO3 0.003g-0.006g, ZnSO4·7H2O 0.001g-0.003g, CoCl2·6H2O 0.003g-0.005g, NaMoO4·2H2O 0.0004g-0.0007g, NiCl2·6H2O 0.0002g-0.0005g, MnCl2·4H2O0.0005g-0.0008g, CuSO4·5H2O 0.0001g-0.0004g.

[0021] In an alternative embodiment, the anode chamber is inoculated with sludge from a sewage treatment plant as electrochemically active microorganisms.

[0022] In an optional embodiment, the volume ratio of the anolyte to the sludge is 8-10:1.

[0023] In an optional embodiment, the pH of the sludge is 6.5-7.5, the conductivity is 0.7 mS / cm-1.2 mS / cm, and the chemical oxygen demand is 150 mg / L-350 mg / L.

[0024] In an optional embodiment, the cathode liquid includes at least one of an aqueous solution of potassium ferrocyanide, an aqueous solution of sodium chloride, an aqueous solution of dipotassium hydrogen phosphate, and an aqueous solution of sodium dihydrogen phosphate.

[0025] In an optional embodiment, the concentration of the cathode liquid is 10mM-60mM.

[0026] In an optional embodiment, the step of enriching the carbon-based material with microorganisms is carried out in an anaerobic environment.

[0027] In an optional embodiment, the enrichment temperature is 20°C-25°C.

[0028] In an optional embodiment, in the anode bioaccumulation step, when the voltage drops below 150 mV, one cycle is completed, and 200 mL of anode solution is added until the voltage of the microbial fuel cell can maintain 300 mV-600 mV for three consecutive cycles.

[0029] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0030] 1. The present invention provides a method for recovering scandium using a microbial electrolysis cell. The microbial electrolysis cell includes an anode chamber and a cathode chamber, wherein the anode chamber includes an anode electrode and the cathode chamber includes a cathode electrode. The method includes the following steps: injecting organic wastewater into the anode chamber, wherein the anode electrode includes a carbon-based material enriched by microorganisms; injecting scandium-containing wastewater into the cathode chamber; applying an external voltage to the microbial electrolysis cell for electrolysis, and collecting Sc(OH)3 generated in the cathode chamber after the electrolysis is completed. The present invention uses the carbon-based material enriched by microorganisms as the anode electrode and utilizes the electron donor in the organic wastewater. The electrons are transmitted to the cathode through an external circuit, generating hydrogen at the cathode and simultaneously generating a large amount of OH. - Sc in scandium-containing wastewater 3+ With OH - The Sc(OH)3 precipitate is generated by combination, and after solid-liquid separation, the precipitate is heated to obtain Sc2O3; it can effectively degrade organic pollutants from wastewater, recover scandium in rare earth mine wastewater, and realize resource utilization; at the same time, the bioelectrochemical method has low energy consumption, and the electrons generated by the anode microorganisms in degrading organic matter can greatly reduce the amount of external power supply, avoid the use of strong acid, avoid multi-stage extraction, and the process operation is simple and environmentally friendly.

[0031] 2. The present invention provides a method for recovering scandium using a microbial electrolytic cell, wherein the cathode liquid includes at least one of an aqueous solution of potassium ferrocyanide, an aqueous solution of sodium chloride, an aqueous solution of dipotassium hydrogen phosphate, and an aqueous solution of sodium dihydrogen phosphate; the function of the solute is to provide cations and enhance the conductivity. DETAILED DESCRIPTION

[0032] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0033] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0034] In order to solve the problems existing in the above-mentioned related art, according to a first aspect of the present invention, the present invention provides a method for recovering scandium using a microbial electrolysis cell, comprising the following steps:

[0035] (1) Construction of a bioelectrochemical system: A double-chamber cubic reactor is fixed by combining a reactor module, a stainless steel nut screw and a rubber gasket. The reactor module consists of an anode chamber, an anode electrode, a cathode chamber and a cathode electrode. A cation exchange membrane is set between the chambers. The chamber size is (1-10) cm × (1-10) cm × (1-15) cm, and the working volume is 1 mL-1200 mL. The anode chamber and the cathode chamber are made of organic glass. The anode electrode includes a carbon-based material enriched with microorganisms, and the carbon-based material includes at least one of a carbon brush, a carbon felt, a carbon rod and a graphite felt. The cathode electrode includes a composite metal material. The invention comprises at least one of a stainless steel mesh, a titanium sheet, Pt / C, and a metal organic framework material; the metal organic framework material comprises at least one of MIL-100(Fe), MIL-101(Fe), Cu-HHTP, and ZIF-67; the anolyte is organic wastewater, and the catholyte is a waste liquid containing scandium; the reactor module is connected to a data collection system via an external resistor to collect voltage and calculate current; the external resistor is 1Ω-1000Ω; the concentration of scandium ions in the waste liquid containing scandium is 5mg / L-200mg / L; and the chemical oxygen demand in the organic wastewater is 100mg / L-2000mg / L.

[0036] (2) Preparation of the anode: The anode is an important component of the bioelectrochemical system and is directly related to the adsorption capacity of microorganisms and the electron transfer efficiency between microorganisms and electrodes. The anode electrode is tightly wound on the anode electrode brush. The length of the anode electrode brush is 0.1cm-10cm and the diameter is 0.1cm-10cm. The prepared anode electrode brush is then pretreated to remove surface impurities. Specifically, the anode electrode brush is soaked in 1mol / L NaOH solution and 1mol / L HCl solution for 1h-6h, then cleaned with deionized water, and then boiled in deionized water for 2h-6h. Fresh deionized water is replaced every half an hour. Finally, the anode electrode brush is heated in a muffle furnace at 500℃-600℃ for 10min-30min to obtain the anode electrode.

[0037] (3) Preparation of cathode electrode: The cathode electrode is cut into (0.1-10) cm × (0.1-10) cm × (0.1-10) cm, punched, and fixed with glue and wire to make a cathode electrode brush. The prepared cathode electrode brush is pretreated to remove surface impurities, specifically including: soaking in 1 mol / L NaOH solution and 1 mol / L HCl solution for 4 h to 8 h, respectively, and then placed in an ultrasonic cleaner and cleaned with deionized water until neutral, to obtain a cathode electrode;

[0038] (4) Carbon-based materials for microbial enrichment: The positive electrode is installed in the anode chamber, and the negative electrode is installed in the cathode chamber. After the reactor is assembled, the inoculated sludge and the anode liquid are injected into the anode chamber at a volume ratio of 1:8-10. In order to maintain the anaerobic environment of the anode chamber, the nitrogen blower is connected to the anode chamber for 10min-30min and microbial enrichment is carried out; the cathode liquid includes at least one of potassium ferrocyanide aqueous solution, sodium chloride aqueous solution, dipotassium hydrogen phosphate aqueous solution, and sodium dihydrogen phosphate aqueous solution, and the concentration of the cathode liquid is 10mM-60mM; the microbial enrichment is carried out at room temperature (20℃-25℃), and the microbial enrichment is carried out by using Wan Use a meter to record the voltage change. When the voltage drops below 150mV, one cycle is complete. Add 200mL of anolyte and continue to observe the change in the output voltage until the reactor voltage can maintain 300mV-600mV for three consecutive cycles. Microbial enrichment is complete. The pH of the inoculated sludge is 6.5-7.5, the conductivity is 0.7mS / cm-1.2mS / cm, and the chemical oxygen demand (COD) is 150mg / L-350mg / L. The raw materials of the anolyte in 1L of deionized water include: KH2PO4 2.0g-2.5g, Na2HPO4 2.5g-3.0g, MgSO4·7H2O 0.3g-0.7g, NH4Cl 0.8g-1.2g, NaHCO30.4g-0.6g, CaCl2·2H2O 0.01g-0.03g, ferric ammonium citrate 0.03g-0.06g, H3BO30.003g-0.006g, ZnSO4·7H2O 0.001g-0.003g, CoCl2·6H2O 0.003g-0.005g, NaMoO4·2H2O 0.0004g-0.0007g, NiCl2·6H2O 0.0002g-0.0005g, MnCl2·4H2O0.0005g-0.0008g, CuSO4·5H2O 0.0001g-0.0004g;

[0039] (5) After the microbial enrichment is completed, the solution in the anode chamber is replaced with organic wastewater with a COD of 100 mg / L-2000 mg / L, and the solution in the cathode chamber is replaced with wastewater containing scandium. 3+ The concentration is 5 mg / L-200 mg / L, the power supply voltage is 1.0 V-2.5 V at 30 ° C, and after running for 1 h-24 h, centrifuge for 10 min-30 min at a speed of 4000 rpm-10000 rpm. The solid after centrifugation is dried at 100 ° C-110 ° C for 18 h-36 h to obtain Sc(OH)3 solid, and the solid powder is calcined at 500 ° C-600 ° C for 1 h-3 h to obtain Sc2O3 powder.

[0040] The present invention uses carbon-based materials enriched with microorganisms as the positive electrode, utilizes electron donors in organic wastewater, and transmits electrons to the cathode through an external circuit, generating hydrogen at the cathode and a large amount of OH at the same time. - Sc in scandium-containing wastewater 3+ With OH - The Sc(OH)3 precipitate is generated by combining and, after solid-liquid separation, the precipitate is heated to obtain Sc2O3; it can effectively degrade organic pollutants from wastewater and recover scandium from rare earth mine wastewater, realizing resource utilization; at the same time, the bioelectrochemical method has low energy consumption, and the electrons generated by the degradation of organic matter by anode microorganisms can significantly reduce the amount of external power supply, avoid the use of strong acid, avoid multi-stage extraction, and the process operation is simple and environmentally friendly. Bioelectrochemical cathode:

[0041] 2H2O+2e-→H2↑+2OH - (1)

[0042] Sc 3+ +3OH - →Sc(OH)3↓ (2)

[0043] Incineration of recovered precipitate:

[0044] Sc(OH)3→Sc2O3+3H2O (3)

[0045] Compared with the reagent- and energy-intensive nature of commonly used recovery processes (solvent extraction, ion exchange, etc.), bioelectrochemical methods can effectively avoid the large-scale use of toxic chemicals, the generation of secondary waste, large pH values or thermal fluctuations due to their versatility, modularity, reversibility and scalability.

[0046] The cathode liquid of the present invention comprises at least one of potassium ferricyanide aqueous solution, sodium chloride aqueous solution, dipotassium hydrogen phosphate aqueous solution and sodium dihydrogen phosphate aqueous solution; the solute functions to provide cations and enhance the conductivity.

[0047] In the present invention, the organic wastewater is domestic organic wastewater taken from a sewage treatment plant, and the inoculated sludge is anaerobic sludge from a sewage treatment plant.

[0048] The present invention is further described in detail below with reference to specific examples. These examples should not be construed as limiting the scope of protection claimed in the present invention.

[0049] Example 1

[0050] This embodiment provides a method for recovering scandium using a microbial electrolysis cell, comprising the following steps:

[0051] (1) A carbon brush with a length of 3 cm and a diameter of 2 cm was tightly wound around the anode electrode brush. -1Soak in NaOH solution for 6 h to remove impurity ions; then -1 Soak in HCl solution for 6 hours, ultrasonically clean with deionized water until neutral; then boil in deionized water for 3 hours, changing the water every 30 minutes, and finally heat in a muffle furnace at 500℃ for 10 minutes to obtain the positive electrode;

[0052] (2) Punch holes in a 3cm×3cm×1mm stainless steel mesh and fix it with glue and wire to make a cathode electrode brush. -1 Soak in NaOH solution for 5 h to remove impurity ions; then -1 Soak in HCl solution for 6 h, and ultrasonically clean with deionized water until neutral to obtain a cathode electrode;

[0053] (3) The positive electrode was installed in the anode chamber, and the negative electrode was installed in the cathode chamber. The chamber size was 10 cm × 10 cm × 5 cm, and the working volume was 400 mL. After the reactor was assembled, 40 mL of inoculated sludge and 360 mL of anolyte were injected into the anode chamber, and nitrogen was introduced for 10 minutes to enrich the microorganisms. The cathode liquid was 50 mM 400mL potassium ferricyanide aqueous solution was added, and the reactor was placed in a 25℃ constant temperature incubator. The voltage change was recorded with a multimeter. When the voltage dropped below 150mV, one cycle was completed. 200mL of anolyte was added, and the change in the output voltage was continuously observed until the reactor voltage could maintain 300mV-600mV for three consecutive cycles, indicating that microbial enrichment was complete. Among them, the pH of the inoculated sludge was 7.20, the conductivity was 0.9mS / cm, and the COD was 300mg / L. The raw materials of the anolyte were composed of 2.0g KH2PO4, 2.7g Na2HPO4, 0.5g MgSO4·7H2O, 1.0g NH4Cl, 0.5g NaHCO3, and CaCl2·2H2O per 1L of deionized water. 0.02g, ammonium ferric citrate 0.05g, H3BO3 0.004g, ZnSO4·7H2O 0.002g, CoCl2·6H2O 0.004g, NaMoO4·2H2O 0.0005g, NiCl2·6H2O 0.0004g, MnCl2·4H2O 0.0006g and CuSO4·5H2O 0.0002g;

[0054] (4) After the microbial enrichment is completed, the solution in the anode chamber is replaced with 400 mL of organic wastewater with a COD of 200 mg / L, and the solution in the cathode chamber is replaced with 400 mL of wastewater containing scandium. 3+The concentration is 10 mg / L, at 30 ° C, the external voltage applied by the power supply is 1.2 V, the external resistance is 10 Ω, after running for 24 hours, the cathode chamber solution is centrifuged at 10000 rpm for 10 minutes, the supernatant is discarded, the solid after centrifugation is washed with deionized water and centrifuged again, repeated 2 times, after 3 centrifugations, the solid is dried at 105 ° C for 24 hours to obtain Sc(OH)3 solid, and the solid powder is calcined at 600 ° C for 1 hour to obtain Sc2O3 powder. After testing, the COD removal rate in the anode wastewater and the cathode Sc 3+ The removal rate and Sc2O3 powder production results are shown in Table 1. It can be seen from Table 1 that after the system runs for 24 hours, the anode COD removal rate of the system is higher than 75%, and the cathode Sc 3+ The removal rate is higher than 90%, and the Sc2O3 powder yield is as high as 14.15 mg / L, indicating that this method can simultaneously achieve the functions of wastewater treatment and scandium recovery; Among them, COD removal rate = (COD content in organic wastewater before electrolysis - COD content in organic wastewater after electrolysis) / COD content in organic wastewater before electrolysis × 100%, cathode Sc 3+ Removal rate = (Sc in the waste liquid containing scandium before electrolysis 3+ Content-Sc in scandium-containing wastewater after electrolysis 3+ Content) / Sc in scandium-containing wastewater before electrolysis 3+ Content × 100%.

[0055] Table 1 Anode COD removal rate, cathode Sc in Example 1 3+ Removal rate and Sc2O3 powder production test results

[0056] COD removal rate % <![CDATA[Cathode Sc 3+ Removal rate %]]> <![CDATA[Sc2O3 powder production mg / L]]> 77.3 92.3 14.15

[0057] Example 2

[0058] This embodiment provides a method for recovering scandium using a microbial electrolytic cell, which is substantially the same as the steps in Example 1, except that in step (5), the external voltage applied is 1.5V.

[0059] After testing, the COD removal rate in the anode wastewater and the cathode Sc 3+ The removal rate and Sc2O3 powder production results are shown in Table 2. It can be seen from Table 2 that the present invention can not only effectively reduce the COD content in wastewater, but also has good scandium recovery performance. Increasing the applied voltage is beneficial to improving the cathode Sc 3+ The removal rate is as high as 97.5%, and the Sc2O3 powder production is increased to 14.95 mg / L.

[0060] Table 2 Anode COD removal rate, cathode Sc in Example 2 3+ Removal rate and Sc2O3 powder production test results

[0061] COD removal rate % <![CDATA[Cathode Sc 3+ Removal rate %]]> <![CDATA[Sc2O3 powder production mg / L]]> 78.6 97.5 14.95

[0062] Example 3

[0063] This embodiment provides a method for recovering scandium using a microbial electrolytic cell, which is basically the same as the steps in Example 1, except that in step (5), the Sc2-containing waste liquid is 3+ The concentration is 20mg / L.

[0064] After testing, the COD removal rate in the anode wastewater and the cathode Sc 3+ The removal rate and Sc2O3 powder production results are shown in Table 3. It can be seen from Table 3 that the present invention can effectively reduce the COD in wastewater with different concentrations of scandium-containing wastewater and has good scandium recovery performance, which is higher than 90%. 3+ The increase in concentration increased the Sc2O3 powder yield to 27.66 mg / L.

[0065] Table 3 Anode COD removal rate, cathode Sc in Example 3 3+ Removal rate and Sc2O3 powder production test results

[0066] COD removal rate % <![CDATA[Cathode Sc 3+ Removal rate %]]> <![CDATA[Sc2O3 powder production mg / L]]> 75.7 90.2 27.66

[0067] Example 4

[0068] This embodiment provides a method for recovering scandium using a microbial electrolytic cell, which is substantially the same as the steps in Example 3, except that, in step (2), the 3 cm × 3 cm × 1 mm stainless steel mesh is replaced with a 3 cm × 3 cm × 1 mm titanium sheet.

[0069] After testing, the COD removal rate in the anode wastewater and the cathode Sc 3+ The removal rate and Sc2O3 powder production results are shown in Table 4. It can be seen from Table 4 that replacing the stainless steel mesh with titanium sheet can significantly improve the COD removal rate and scandium recovery rate.

[0070] Table 4 Anode COD removal rate, cathode Sc 3+ Removal rate and Sc2O3 powder production test results

[0071] COD removal rate % <![CDATA[Cathode Sc 3+ Removal rate %]]> <![CDATA[Sc2O3 powder production mg / L]]> 80.1 96.3 29.53

[0072] Example 5

[0073] This embodiment provides a method for recovering scandium using a microbial electrolysis cell, which is substantially the same as the steps in Example 1, except that in step (4), the COD concentration of the anode organic wastewater is 400 mg / L.

[0074] After testing, the COD removal rate in the anode wastewater and the cathode Sc 3+ The removal rate and Sc2O3 powder production results are shown in Table 5. It can be seen from Table 5 that the COD concentration in the anode wastewater is increased, and the wastewater or COD content can be effectively reduced, and the scandium recovery performance is good.

[0075] Table 5 Anode COD removal rate of Example 5, cathode Sc 3+ Analysis results of removal rate and Sc2O3 powder production

[0076] COD removal rate % <![CDATA[Cathode Sc 3+ Removal rate %]]> <![CDATA[Sc2O3 powder production mg / L]]> 75.1 93.2 14.35

[0077] Example 6

[0078] This embodiment provides a method for recovering scandium using a microbial electrolysis cell, comprising the following steps:

[0079] (1) A 5 cm long and 4 cm diameter carbon rod was tightly wound around the anode electrode brush. -1 Soak in NaOH solution for 2 h to remove impurity ions; then -1 Soak in HCl solution for 2 hours, ultrasonically clean with deionized water until neutral; then boil in deionized water for 4 hours, changing the water every 30 minutes, and finally heat in a muffle furnace at 500℃ for 20 minutes to obtain the positive electrode;

[0080] (2) First, the graphite plate was heated to 1 mol·L -1 Soak in NaOH solution for 5 h to remove impurity ions; then -1 The cathode electrode was prepared by soaking the sample in an HCl solution for 6 h, ultrasonically cleaning the sample with deionized water until the sample was neutral, and then coating 50 mg of an iron-based metal-organic framework material MIL-100(Fe) on a 3 cm × 7 cm × 2 mm graphite plate and placing the plate at room temperature for 24 h to obtain a cathode electrode. The preparation method of MIL-100(Fe) comprises the following steps: adding 2.7 g of FeCl3·6H2O, 1.4 g of 1,3,5-benzenetricarboxylic acid, and 60 mL of H2O to a Teflon-lined steel autoclave and heating the plate at 150°C for 12 h. After cooling, the light orange solid product was filtered and recovered by a two-step method. The solid product was further purified in 80°C hot water and 60°C ethanol, respectively, and then dried at 80°C to obtain the metal-organic framework material MIL-100(Fe).

[0081] (3) The positive electrode was installed in the anode chamber, and the negative electrode was installed in the cathode chamber. The chamber size was 8cm×10cm×5cm, and the working volume was 300mL. After the reaction electrodes were assembled, 30mL of inoculated sludge and 270mL of anolyte were injected into the anode chamber, and nitrogen was introduced for 20 minutes to enrich the microorganisms. The cathode liquid was 300mL of 10mM potassium dihydrogen phosphate aqueous solution. The reactor was placed in a 20℃ constant temperature incubator, and the voltage change was recorded using a multimeter. When the voltage dropped below 150mV, a cycle was completed. 200mL of anolyte was added, and the change in its output voltage was continued to be observed until the reactor voltage could maintain 300mV-600mV for three consecutive cycles. The microorganism enrichment was completed. Among them, the pH of the inoculated sludge was 6.5, the conductivity was 1.2mS / cm, and the COD was 350mg / L. The raw materials of the anolyte in each 1L of deionized water included: KH2PO42.3g, Na2HPO4 3.0g, MgSO4·7H2O0.3g, NH4Cl 1.2g, NaHCO3 0.4g, CaCl2·2H2O 0.03g, ammonium ferric citrate 0.06g, H3BO3 0.003g, ZnSO4·7H2O0.003g, CoCl2·6H2O0.003g, NaMoO4·2H2O0.0007g, NiCl2·6H2O0.0005g, MnCl2·4H2O0.0008g and CuSO4·5H2O0.0001g;

[0082] (4) After the microbial enrichment is completed, the solution in the anode is replaced with 300 mL of wastewater with a COD of 300 mg / L, and the solution in the cathode is replaced with 300 mL of wastewater containing scandium. 3+ The concentration is 100 mg / L. At 30°C, the external voltage applied by the power supply is 1.4V, the external resistance is 10Ω, and after running for 12 hours, the cathode solution is centrifuged at 7000rpm for 20 minutes, the supernatant is discarded, the solid after centrifugation is washed with deionized water and centrifuged again, repeated 2 times, and the solid after 3 centrifugation is dried at 110°C for 24 hours to obtain Sc(OH)3 solid. The solid powder is calcined at 600°C for 2 hours to obtain Sc2O3 powder. After testing, the COD removal rate in the anode wastewater and the cathode Sc 3+ The removal rate and Sc2O3 powder production results are shown in Table 6. It can be seen from Table 6 that the COD removal rate of this embodiment is 82.3%, and it has a good recovery effect on high-concentration scandium-containing wastewater. 3+ The removal rate reached 95.1%, and 145.82 mg / L of Sc2O3 powder could be recovered.

[0083] Table 6 Anode COD removal rate, cathode Sc 3+ Removal rate and Sc2O3 powder production test results

[0084] COD removal rate % <![CDATA[Cathode Sc 3+ Removal rate %]]> <![CDATA[Sc2O3 powder production mg / L]]> 82.3 95.1 145.82

[0085] Example 7

[0086] This embodiment provides a method for recovering scandium using a microbial electrolysis cell, comprising the following steps:

[0087] (1) A graphite felt with a length of 7 cm and a diameter of 5 cm was tightly wound around the anode electrode brush. -1 Soak in NaOH solution for 2 h to remove impurity ions; then -1 Soak in HCl solution for 2 hours, ultrasonically clean with deionized water until neutral; then boil in deionized water for 3 hours, changing the water every 30 minutes, and finally heat in a muffle furnace at 550℃ for 30 minutes to obtain the positive electrode;

[0088] (2) Punch a hole in a 3cm×3cm×2mm titanium sheet and fix it with glue and wire to make a cathode electrode brush. -1 Soak in NaOH solution for 2 h to remove impurity ions; then -1 Soak in HCl solution for 2 h, and ultrasonically clean with deionized water until neutral to obtain a cathode electrode;

[0089] (3) The positive electrode was installed in the anode chamber, and the negative electrode was installed in the cathode chamber. The chamber size was 5 cm × 5 cm × 10 cm, and the working volume was 200 mL. After the reactor was assembled, 20 mL of inoculated sludge and 180 mL of anolyte were injected into the anode chamber, and nitrogen was introduced for 30 minutes for microbial enrichment. The cathode liquid was 60 mM 200mL sodium chloride aqueous solution, place the reactor in a 23℃ constant temperature incubator, use a multimeter to record the voltage change, and complete a cycle when the voltage drops below 150mV. Add 200mL of anolyte and continue to observe the change in its output voltage until the reactor voltage can maintain 300mV-600mV for three consecutive cycles, indicating that microbial enrichment is complete; Among them, the pH of the inoculated sludge is 7.5, the conductivity is 0.7mS / cm, and the COD is 150mg / L; the raw materials of the anolyte in 1L of deionized water include: KH2PO42.5g, Na2HPO42.5g, MgSO4·7H2O0.7g, NH4Cl0.8g, NaHCO30.6g, CaCl2·2H2O 0.01g, ammonium ferric citrate 0.03g, H3BO3 0.006g, ZnSO4·7H2O 0.001g, CoCl2·6H2O 0.005g, NaMoO4·2H2O 0.0004g, NiCl2·6H2O 0.0002g, MnCl2·4H2O 0.0005g and CuSO4·5H2O 0.0004g;

[0090] (4) After the microbial enrichment is completed, the solution in the anode chamber is replaced with 200 mL of organic wastewater with a COD of 2000 mg / L, and the solution in the cathode chamber is replaced with 200 mL of wastewater containing scandium. 3+ The concentration is 180 mg / L. At 30°C, the external voltage applied by the power supply is 1.6 V, and the external resistance is 100 Ω. After running for 1 hour, the cathode chamber solution is centrifuged at 4000 rpm for 30 minutes, the supernatant is discarded, and the solid after centrifugation is washed with deionized water and centrifuged again. This is repeated 2 times. After 3 centrifugations, the solid is dried at 100°C for 18 hours to obtain Sc(OH)3 solid. The solid powder is calcined at 550°C for 1 hour to obtain Sc2O3 powder. After testing, the COD removal rate in the anode wastewater and the cathode Sc 3+ The removal rate and Sc2O3 powder production results are shown in Table 7. It can be seen from Table 7 that the COD removal rate of the anode of this embodiment is 80.9%, and the cathode Sc 3+ The removal rate is 93.8%, and the Sc2O3 powder yield is 258.89 mg / L.

[0091] Table 7 Anode COD removal rate, cathode Sc in Example 7 3+ Removal rate and Sc2O3 powder production test results

[0092] COD removal rate % <![CDATA[Cathode Sc 3+ Removal rate %]]> <![CDATA[Sc2O3 powder production mg / L]]> 80.9 93.8 258.89

[0093] Comparative Example 1

[0094] This comparative example provides a method for recovering scandium using a microbial electrolytic cell. The steps are basically the same as those in Example 1, except that step (4) is omitted. The organic wastewater and the scandium-containing wastewater are injected into the anode chamber and the cathode chamber respectively before enrichment. The COD removal rate in the anode wastewater and the Sc removal rate in the cathode chamber are respectively 3+ The removal rate and Sc2O3 powder production results are shown in Table 8.

[0095] As can be seen from Table 8, in the state of no microbial enrichment at the anode, due to the absence of microbial degradation process and lack of microbial-electrode interface regulation (such as biofilm formation mechanism), it only relies on physical and chemical processes (such as adsorption, precipitation) or non-biological electrochemical reactions. The COD removal efficiency is extremely low, only 5.3%, and the cathode scandium recovery efficiency is significantly reduced. 3+ The removal rate is 10.1%, and the Sc2O3 powder yield is 1.55 mg / L.

[0096] Table 8 Anode COD removal rate, cathode Sc 3+ Removal rate and Sc2O3 powder production test results

[0097] COD removal rate % <![CDATA[Cathode Sc 3+ Removal rate %]]> <![CDATA[Sc2O3 powder production mg / L]]> 5.3 10.1 1.55

[0098] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for recovering scandium using a microbial electrolytic cell, wherein the microbial electrolytic cell comprises an anode chamber and a cathode chamber, wherein the anode chamber comprises a positive electrode and the cathode chamber comprises a negative electrode; The method comprises the following steps: Injecting organic wastewater into the anode chamber, wherein the anode comprises a carbon-based material enriched with microorganisms; injecting scandium-containing wastewater into the cathode chamber; An external voltage is applied to the microbial electrolysis cell to perform electrolysis, and after the electrolysis is completed, Sc(OH)3 generated in the cathode chamber is collected.

2. The method for recovering scandium using a microbial electrolytic cell according to claim 1, wherein: In the scandium-containing waste liquid, the concentration of scandium ions is 5 mg / L-200 mg / L.

3. The method for recovering scandium using a microbial electrolytic cell according to claim 1, wherein: The electrolysis temperature is 20°C-40°C and the time is 1h-24h; And / or, the applied external voltage is 1.0V-2.5V, and the external resistance is 1Ω-1000Ω.

4. The method for recovering scandium using a microbial electrolytic cell according to claim 1, wherein: The chemical oxygen demand of the organic wastewater is 100 mg / L-2000 mg / L.

5. The method for recovering scandium using a microbial electrolytic cell according to claim 1, characterized in that: After the electrolysis is completed, the Sc(OH)3 is obtained by centrifugation and drying; and the Sc(OH)3 is calcined to obtain Sc2O3; The centrifugation time is 10 min-30 min, and the rotation speed is 4000 rpm-10000 rpm; And / or, the drying temperature is 100° C.-110° C., and the drying time is 18 h-36 h; And / or, the calcination temperature is 500° C.-600° C., and the calcination time is 1 h-3 h.

6. The method for recovering scandium using a microbial electrolytic cell according to claim 1, wherein: The carbon-based material includes at least one of a carbon brush, a carbon felt, a carbon rod, and a graphite felt; And / or, the cathode electrode of the microbial electrolysis cell comprises a composite metal material; the composite metal material comprises at least one of a stainless steel mesh, a titanium sheet, Pt / C, and a metal-organic framework material.

7. The method for recovering scandium using a microbial electrolytic cell according to claim 1, characterized in that: The microbial-enriched carbon-based material is prepared by the following steps: injecting anolyte and electrochemically active microorganisms into the anode chamber, injecting catholyte into the cathode chamber, and testing the voltage of the microbial electrolysis cell until the voltage is maintained at 300mV-600mV, indicating that the enrichment is complete.

8. The method for recovering scandium using a microbial electrolytic cell according to claim 7, characterized in that: In every 1L of deionized water, the raw material composition of the anolyte includes: KH2PO4 2.0g-2.5g, Na2HPO4 2.5g-3.0g, MgSO4·7H2O 0.3g-0.7g, NH4Cl 0.8g-1.2g, NaHCO3 0.4g-0.6g, CaCl2·2H2O 0.01g-0.03g, ammonium ferric citrate 0.03g-0.06g, H3BO3 0.003g-0.006g, ZnSO4·7H2O 0.001g-0.003g, CoCl2·6H2O 0.003g-0.005g, NaMoO4·2H2O 0.0004g-0.0007g, NiCl2·6H2O 0.0002g-0.0005g, MnCl2·4H2O0.0005g-0.0008g, CuSO4·5H2O 0.0001g-0.0004g.

9. The method for recovering scandium using a microbial electrolytic cell according to claim 7, characterized in that: The anode chamber is inoculated with sewage treatment plant sludge as electrochemically active microorganisms; and / or, the volume ratio of the anolyte to the sludge is 8-10:1; and / or, the sludge has a pH of 6.5-7.5, a conductivity of 0.7 mS / cm-1.2 mS / cm, and a chemical oxygen demand of 150 mg / L-350 mg / L; And / or, the cathode liquid comprises at least one of an aqueous solution of potassium ferrocyanide, an aqueous solution of sodium chloride, an aqueous solution of dipotassium hydrogen phosphate, and an aqueous solution of sodium dihydrogen phosphate; and / or, the concentration of the cathode liquid is 10 mM-60 mM; and / or, the step of enriching the carbon-based material with microorganisms is carried out in an anaerobic environment; And / or, the enrichment temperature is 20°C-25°C.

10. The method for recovering scandium using a microbial electrolytic cell according to claim 7, characterized in that: In the step of preparing the microbial-enriched carbon-based material, a cycle is completed when the voltage drops below 150 mV, and 200 mL of anode liquid is added until the voltage of the microbial fuel cell can maintain 300 mV-600 mV for three consecutive cycles.