CN103266331B - The self-driven microorganism electrolysis cell coupled system of a kind of microbiological fuel cell reclaims the method for simple substance cobalt from cobalt acid lithium - Google Patents

Abstract

A method for recovering elemental cobalt from lithium cobaltate by using microbial fuel cells (MFCs) self-driven and coupled with microbial electrolysis cells (MECs). The anode is directly connected to the cathode, and the cathode of the MFCs is connected to the anode of the MECs through a resistor. The catholyte and lithium cobalt oxide particles are installed in the cathode chamber of MFCs; the clarifier sludge of the sewage treatment plant is inoculated in the anode chamber as electrochemically active microorganisms. The cathode compartment of MECs is filled with an aqueous solution containing Co(II); the anode compartment is inoculated with clarifier sludge from a sewage treatment plant as electrochemically active microorganisms. Both anode and cathode materials are graphite materials. The invention provides an effective way for the in-situ utilization of the output electric energy of the MFCs, and also provides a broad space for the application of the MECs without additional electric energy input and without limitations on the acidity of the catholyte.

Description

A method for recovering elemental cobalt from lithium cobaltate by a microbial fuel cell self-driven microbial electrolytic cell coupling system

technical field

The invention belongs to the technical field of microbial electrochemistry, and specifically utilizes the respective characteristics of microbial fuel cells MFCs and microbial electrolytic cells MECs to combine Co(III) leaching of lithium cobaltate particles into liquid phase Co(II), and from liquid phase Co( II) The chemical potential change of the reduction to elemental cobalt, which is driven by the leaching of Co(III) to Co(II) MFCs and coupled with the MECs process of Co(II) reduction to elemental cobalt.

Background technique

Both microbial fuel cells (Microbial Fuel Cells, MFCs) and microbial electrolysis cells (Microbial Electrolysis Cells, MECs) include an anode chamber, an anode electrode, a cathode chamber, a cathode electrode, and a proton exchange membrane. The difference is that the Gibbs free energy of the reaction between the cathode and anode of MFCs is less than zero, the reaction can proceed spontaneously, and the system outputs electric energy; on the contrary, the Gibbs free energy of the reaction between the cathode and anode of MECs is greater than zero, and the reaction cannot be spontaneous To proceed, the outside world needs to input energy to drive the reaction to proceed. The MFCs that output electrical energy are used to drive and couple the MECs that require input electrical energy. While the electrical energy of MFCs can be directly used in situ, valuable chemicals can be synthesized at the cathode of MFCs and MECs, and organic pollutants can also be removed at the anode of MFCs and MECs. Cleanliness is an inevitable requirement for sustainable social development.

Cobalt is an important rare metal in the production of lithium-ion batteries, accounting for 15–20% of the battery. With the mass production and widespread use of lithium-ion batteries, the environmental problems brought about by them are becoming more and more serious. At the same time, my country is the largest producer, consumer and exporter of lithium-ion batteries, accounting for more than 1/3 of the global share, and has the most urgent demand for cobalt. Clean and efficient recovery of the rare metal cobalt in waste lithium-ion batteries not only effectively solves battery pollution, but also recycles waste, which has obvious environmental, economic and social benefits.

Cobalt exists as lithium cobalt oxide (LiCoO ₂ ) in lithium-ion batteries. The traditional recovery methods mainly include physical, chemical, and biological methods. The main method is to reduce Co(III) in LiCoO ₂ to liquid phase Co(III) through acid leaching. II), and the subsequent recovery of cobalt by liquid phase Co(II) through advanced treatment (chemical deposition, solvent extraction, electrodeposition), has high energy consumption and cost, secondary pollution, many by-products, long cycle, low efficiency, The process is cumbersome and other disadvantages. As an emerging technology, although MFCs can reduce Co(III) in LiCoO ₂ particles to dissolved Co(II), advanced treatment is required to recover cobalt from the liquid phase; moreover, the output power of MFCs has not been effectively collected and utilized. Although MECs can leach _LiCoO2 and obtain elemental cobalt, the system needs to input a lot of energy; moreover, the catholyte needs to be limited to a strong acidic environment. It is still a hot spot to seek a cleaner, short-range material preparation and lithium cobalt oxide resource utilization technology.

Taking pH 2.0 as an example, the theoretical redox potential of Co(III) to Co( _II ) in LiCoO ₂ is 1.845 V, which is comparable to the redox potential (–0.30 V) can be constructed as MFCs; while the reduction of Co(II) has nothing to do with pH, the theoretical redox potential of Co(II) (calculated at 50mg/L) reduced to elemental cobalt at any pH is only –0.373V, which is lower than that of organic matter (Taking sodium acetate as an example) redox potential (–0.30V), it is necessary to construct MECs, and the reaction is driven by input energy. Therefore, if MFCs leached from Co(III) to Co(II) are self-driven and coupled with MECs that reduce Co(II) to elemental cobalt, the clean recovery of elemental cobalt in spent lithium-ion batteries can be achieved, and the original It provides an effective way to utilize the output power of MFCs; meanwhile, it also provides a broad space for the application of MECs with no additional power input and no restriction on the acidity of catholyte.

Contents of the invention

The invention provides a clean microbial fuel cell self-driven microbial electrolytic cell technology for recovering elemental cobalt from lithium cobalt oxide without external energy consumption.

The present invention uses MFCs to self-drive MECs to reclaim elemental cobalt from lithium cobalt oxide. It is to add inorganic acid solutions such as hydrochloric acid in the cathode chamber of MFCs. The cathode electrodes are conductive materials such as carbon rods and carbon felts, and the amount of lithium cobalt oxide is ≤ 100g. /L (w/v), the particle size of lithium cobaltate is 8-9 μm, and the lithium cobaltate particles are attached to the surface of the cathode electrode.

Add CoCl ₂ solution in the cathode chamber of MECs, and the cathode electrode is a conductive material such as carbon rod.

The anode compartments of MFCs and MECs are filled with electrochemically active microorganisms and anolyte, and the anode electrodes are conductive materials such as carbon rods and carbon felts.

The cathode of the MFCs is connected to the anode of the MECs through a series resistance coupling, and the current in the circuit is collected and calculated through the resistance.

The anode chamber is inoculated with sewage treatment plant clarifier sludge as electrochemically active microorganisms.

The pH of the clarifier sludge: 6.8-7.0; electrical conductivity: 0.80-0.93mS/cm; suspended solids: 30-35g/L; chemical oxygen demand (COD): 150-300mg/L.

The composition of the anolyte is: 12.0mM sodium acetate; 5.8mM NH ₄ Cl; 1.7mM KCl; 17.8mMNaH ₂ PO ₄ ·H ₂ O; 32.3mM Na ₂ HPO ₄ ; mineral elements: 12.5mL/L (MgSO ₄ : 3.0g/L; MnSO ₄ ·H ₂ O: 0.5g/L; NaCl: 1.0g/L; FeSO ₄ ·7H ₂ O: 0.1g/L; CaCl ₂ ·2H ₂ O: 0.1g/L; CoCl ₂ 6H ₂ O: 0.1g/L; ZnCl ₂ : 0.13g/L; CuSO ₄ 5H ₂ O: 0.01g/L; KAl(SO ₄ ) ₂ 12H ₂ O: 0.01g/L; H ₃ BO ₃ : 0.01g/L; Na ₂ MoO ₄ : 0.025g/L; NiCl ₂ 6H ₂ O: 0.024g/L; Na ₂ WO ₄ 2H ₂ O: 0.024g/L); vitamins: 12.5mL/L ( The composition is vitamin B ₁ : 5.0g/L; vitamin B ₂ : 5.0g/L; vitamin B ₃ : 5.0g/L; vitamin B ₅ : 5.0g/L; vitamin B ₆ : 10.0g/L; vitamin B ₁₁ : 2.0g/L; vitamin H: 2.0g/L; p-aminobenzoic acid: 5.0g/L; lipoic acid: 5.0g/L; aminotriacetic acid: 1.5g/L).

The MFCs and MECs anode chambers of the present invention need to maintain an oxygen-free environment during operation, and anaerobic conditions can be realized by feeding nitrogen.

The flow process of the MFCs operating stage of the present invention is as follows: the organic matter in the anolyte is oxidized by microorganisms in the anode chamber, the protons produced in the process pass through the proton permeable membrane and enter the cathode chamber, and the electrons are introduced into the cathode electrode through an external circuit. On the surface of the cathode electrode, Co(III) attached to lithium cobaltate particles reacts with the electrons provided by the cathode electrode and the proton hydrogen in the solution, and is reduced to dissolved Co(II). The process flow of the MECs operating stage of the present invention is as follows: the organic matter in the anolyte is oxidized by microorganisms in the anode chamber, and the electrons generated by the MFCs are introduced into the cathode of the MECs. On the surface of the cathode electrode, the dissolved Co(II) obtains the electrons provided by the cathode electrode and is reduced to elemental cobalt, thereby realizing the MFCs self-driven MECs coupling process of recovering elemental cobalt from lithium cobaltate. The anode chamber of MFCs and MECs can be municipal sewage containing organic matter, while the cathode chamber of MFCs and MECs takes lithium cobalt oxide as the starting substrate to reduce Co(III) to Co(II) and Co(II) to elemental cobalt respectively. Reaction, the system uses MFCs electrical energy in situ, without additional energy input to MECs, and without maintaining the strong acidic environment of MECs catholyte. While recycling the valuable metal cobalt in waste lithium-ion batteries, it can also treat municipal and other organic sewage, achieving better environmental pollution control and resource utilization effects. The process is clean and has both environmental and ecological benefits, social benefits and economic benefits.

Description of drawings and attached tables

Fig. 1 is a structural schematic diagram of recovering elemental cobalt from lithium cobaltate particles by the MFCs self-driven MECs coupling system of the present invention.

FIG. 2 is a time-varying graph of Co(II) leaching of lithium cobaltate in the MFCs of Example 1. FIG.

FIG. 3 is a time-varying graph of Co(II) reduction in MECs of Example 1. FIG.

FIG. 4 is the polarization curve of the MFCs of Example 1. FIG.

5 is a cyclic voltammetry curve of the MECs of Example 1.

In the figure: 1 carbon rod; 2MFCs anode chamber; 3 carbon felt; 4 ion exchange membrane; 5MFCs cathode chamber; 6 carbon felt; 7 lithium cobaltate particles; 8 carbon rod; 9 reference electrode; 10 data acquisition board; Resistance; 12 reference electrode; 13 carbon rod; 14MECs anode chamber; 15 carbon felt; 16 ion exchange membrane; 17MECs cathode chamber;

detailed description

Example 1

Step 1: Construct MFCs and MECs, as shown in Figure 1: MFCs anode chamber 2 and cathode chamber 5, MECs anode chamber 14 and cathode chamber 17 are made of organic glass, the volume of the anode chamber solution of MFCs and MECs is 15mL, MFCs The volume of solution in the cathodic chamber of MFCs and MECs is 25mL, separated by ion exchange membrane (CMI-7000) 4 or 16, and a 10Ω small resistor 11 is connected in series between MFCs and MECs, so as to collect and calculate the current in the circuit.

Step 2: MFCs anode electrode (carbon rod and carbon felt) and cathode electrode (carbon rod and carbon felt) are placed in MFCs anode chamber 2 and cathode chamber 5 respectively, MECs anode electrode (carbon rod and carbon felt) and cathode Electrodes (carbon rods) are placed in the anode chamber 14 and cathode chamber 17 of the MECs. The apparent size of the carbon rod (Beijing Sanye Carbon Material Co., Ltd.) is 0.8cm×3.5cm, the carbon felt (Beijing Sanye Carbon Material Co., Ltd.) has an apparent size of 3.0cm×2.0cm×1.0cm). The reference electrodes 9 and 12 are respectively connected to the MFCs anode chamber and the MECs cathode chamber, and the voltage across the small resistor 11 is collected through the computer and the data acquisition system 10 and the current is calculated; the MFCs anode and MECs cathode potentials are collected according to the reference electrodes.

Step 3: Place 0.25g of lithium cobaltate powder (particle size 8-9μm) and MFCs cathode electrode 8 in 100mL of deionized water, and stir magnetically at 100rpm for 20min. And reduce the cathode electrode of Co(III) in lithium cobaltate.

Step 4: Add 25mL of 0.01M HCl solution to the MFCs cathode chamber, and aerate with nitrogen for 20min.

Step 5: Add CoCl ₂ to 25 mL of boric acid buffer (0.1 M, pH 6.0) in the cathode compartment of the MECs to make the concentration 50 mg/L.

Step 6: Add 15mL of culture solution to the anode compartment of MFCs and MECs respectively, the composition of which is 12.0mM sodium acetate; 5.8mM NH ₄ Cl; 1.7mM KCl; 17.8mM NaH ₂ PO ₄ ·H ₂ O; 32.3mM Na ₂ HPO ₄ ; Mineral elements: 12.5mL/L (MgSO ₄ : 3.0g/L; MnSO ₄ ·H ₂ O: 0.5g/L; NaCl: 1.0g/L; FeSO ₄ ·7H ₂ O: 0.1g/L; CaCl ₂ 2H ₂ O: 0.1g/L; CoCl ₂ 6H ₂ O: 0.1g/L; ZnCl ₂ : 0.13g/L; CuSO ₄ 5H ₂ O: 0.01g/L; KAl(SO ₄ ) ₂ 12H ₂ O: 0.01g/L; H ₃ BO ₃ : 0.01g/L; Na ₂ MoO ₄ : 0.025g/L; NiCl ₂ 6H ₂ O: 0.024g/L; Na ₂ WO ₄ 2H ₂ O: 0.024 g/L); vitamins: 12.5mL/L (vitamin B ₁ : 5.0g/L; vitamin B ₂ : 5.0g/L; vitamin B ₃ : 5.0g/L; vitamin B ₅ : 5.0g/L; vitamin B ₆ : 10.0g/L; vitamin B ₁₁ : 2.0g/L; vitamin H: 2.0g/L; p-aminobenzoic acid: 5.0g/L; lipoic acid: 5.0g/L; aminotriacetic acid: 1.5g/L ). The anode chamber was inoculated with 10g of sludge from the clarification tank of the sewage treatment plant (Dalian Lingshuihe sewage treatment plant). The anolyte was exposed to nitrogen for 20 minutes and then sealed.

Step 7: Assemble the MFCs cathode electrode in step 3 with the MFCs cathode chamber and catholyte in step 4. Allow the device to acclimate and operate at room temperature (20–25°C). When the current drops below 0.02mA, one cycle is completed, and the above-mentioned medium components are added. When the output voltage stabilized at a similar value for three consecutive cycles, it indicated that the anode electrochemically active bacteria had been domesticated and started successfully.

Step 8: Combine the MECs carbon rod cathode in step 2 with the MECs cathode chamber and catholyte in step 5. Allow the device to acclimate and operate at room temperature (20–25°C). When the current at a certain voltage drops below 0.02mA, one cycle is completed, and the above-mentioned medium components are added.

Step 9: Drive the MFCs in step 7 to the MECs in step 8.

Step 10: Take regular samples and analyze the Co(II) content in the liquid phase; characterize the MFCs polarization curve and MECs cyclic voltammetry curve; calculate the specific leaching yield of lithium cobaltate, the specific yield of elemental cobalt, and the cathode coulomb of MFCs Efficiency, system energy efficiency and effective acid utilization, MECs cathode coulombic efficiency and system energy efficiency, and total efficiency of MFCs–MECs system.

The following table 1 is the specific leaching yield of lithium cobaltate in Example 1, the specific yield of elemental cobalt, the MFCs cathode coulombic efficiency, the MFCs system energy efficiency, the acid effective utilization rate of MFCs, the MECs cathode coulombic efficiency, and the MECs system energy efficiency , and the overall efficiency of the MFCs–MECs coupled system.

The MFCs self-driven MECs coupling system in this embodiment recovers elemental cobalt from lithium cobaltate. The reaction at the cathode of MFCs is formula (1), the reaction at the cathode of MECs is formula (2), and the overall reaction formula experienced by cobalt is shown in (3). Specific leaching yield of lithium cobalt oxide (Y _LiCoO2 ), specific yield of cobalt (Y _co ), MFCs cathode coulombic efficiency (CE _MFC ), MECs cathode coulombic efficiency (CE _MEC ), MFCs system energy efficiency (η _MFC ), the energy efficiency of the MECs system (η _MEC ), the total efficiency of the MFCs–MECs coupled system (η _sys ), and the acid availability (AUE) of the MFCs are calculated as shown in equations (4)–(11).

LiCoO ₂ (s)+4H ⁺ +e ^- →Co ²⁺ +Li ⁺ +2H ₂ O (1)

Co ²⁺ +2e ^- → Co (2)

LiCoO ₂ (s)+4H ⁺ +3e ^- →Co+Li ⁺ +2H ₂ O (3)

Δn _Co2+ is the change value (mg/L) of the concentration of cobalt ions in the initial and final states of the reaction in MFC or MEC, 1 is the stoichiometric ratio of lithium cobaltate to Co(II); a ₁ and a ₂ are cobalt acid The stoichiometric ratio of lithium to Co(II), Co(II) to elemental cobalt; b ₁ and b ₂ are the number of electrons (mol/mol) required for the leaching of lithium cobaltate and the reduction of Co(II) respectively ; M _LiCoO2 and M _Co are the relative molecular mass (g/mol) of lithium cobaltate and cobalt, _{Van is the anolyte volume (L) of MFC or MEC, V ca is} the catholyte volume (L) of MFC or MEC, ΔCOD _MFC and ΔCOD _MEC are the change values of chemical oxygen demand in MFC and MEC respectively (g/L), I is the current in the loop (A), t is the reactor running time (s), Δ[H+] is the MFC cathode The change value of hydrogen ion concentration in the initial and final state of the chamber (mol/L), M _LiCoO2 , M _Co and M _O2 are the relative molecular or atomic weights (g/mol) of lithium cobaltate, elemental cobalt and oxygen respectively, and 96485 is the Faraday constant , (C/mol e ^- ); 4 is the number of electrons obtained by oxygen per unit amount of substance (mol/mol), and 1000 is the unit of dimension conversion (mg/g).

Results: The concentration of Co(II) in MFCs gradually increased to 12.7±0.2mg/L within the reaction time of 0-6h (Figure 2). However, in the MECs driven by MFCs with an initial concentration of 50 mg/L, the Co(II) concentration gradually decreased to 35.1±0.2 mg/L (Figure 3), indicating that the MFCs leached lithium cobalt oxide while using output power to drive MECs reduce Co(II). The open circuit voltage of the MFCs system is 0.80V, and the maximum output power is 1.0W/m ³ (4.4A/m ³ ) (Fig. 4). Cyclic voltammetry analysis showed that the redox peaks of MECs cathode appeared at –0.30V and +0.20V, and the maximum current window was –1.35mA (–0.3V) (Figure 5), which was consistent with the reduction potential of Co(II) , indicating that Co(II) was reduced on the electrode surface of MECs.

When the system was running for 6 hours, the specific leaching yield of lithium cobaltate of MFCs was 0.65±0.01g Co/g COD, the cathode Coulombic efficiency was 26±2%, the system energy efficiency was 22±1%, and the effective utilization rate of acid was 9 ±0% (Table 1); the specific cobalt yield of MECs is 0.83±0.14g Co/g COD, the cathode Coulombic efficiency is 44±7%, and the system energy efficiency is 52±1% (Table 1); MFCs–MECs The overall efficiency of the coupling system is 11±2%. These results demonstrate that the MFCs self-driven MECs coupled system can efficiently recover elemental cobalt from lithium cobaltate without energy input to the system. In-situ utilization of MFCs electrical energy and recycling of valuable metal cobalt in waste lithium-ion batteries can also treat municipal sewage; it also provides a broad space for the application of MECs with no additional electrical energy input and no limitation on the acidity of catholyte. The process is clean and pollution-free, and has both environmental and ecological benefits, social benefits and economic benefits.

Claims (5)

1. utilize microbiological fuel cell MFCs self-driven microorganism electrolysis cell MECs coupled system from cobalt acid lithium, reclaim a method for simple substance cobalt, it is characterized in that,

The anode of MFCs is connected with the cathode coupling of MECs;

Add inorganic acid solution at the cathode compartment of MFCs, cathode electrode is electro-conductive material, cobalt acid lithium add-on≤100g/L (w/v), and cobalt acid lithium particle is attached to cathode electrode surface;

CoCl is added at the cathode compartment of MECs ₂solution, cathode electrode is electro-conductive material;

In the anolyte compartment of MFCs and MECs, electrochemical activity microorganism and anolyte are all housed, anode electrode is electro-conductive material;

The negative electrode of MFCs and MECs anode are coupled by series resistance and are connected, and by electric current in this resistor collecting and counting circuit, described series resistance is 1 ~ 1000;

The settling pond mud of inoculation sewage work of anolyte compartment is as electrochemical activity microorganism.

2. method according to claim 1, is characterized in that, described electro-conductive material is carbon-point or carbon felt.

3. method according to claim 1 and 2, is characterized in that, described settling pond sludge pH: 6.8 – 7.0; Specific conductivity: 0.80 – 0.93mS/cm; Suspension solid substance: 30 – 35g/L; Chemical oxygen demand (COD): 150 – 300mg/L.

4. method according to claim 1 and 2, is characterized in that, described MFCs and MECs anolyte composition is: 12.0mM sodium acetate; 5.8mMNH ₄cl; 1.7mMKCl; 17.8mMNaH ₂pO ₄h ₂o; 32.3mMNa ₂hPO ₄; Mineral element: 12.5mL/L, consists of MgSO ₄: 3.0g/L; MnSO ₄h ₂o:0.5g/L; NaCl:1.0g/L; FeSO ₄7H ₂o:0.1g/L; CaCl ₂2H ₂o:0.1g/L; CoCl ₂6H ₂o:0.1g/L; ZnCl ₂: 0.13g/L; CuSO ₄5H ₂o:0.01g/L; KAl (SO ₄) ₂12H ₂o:0.01g/L; H ₃bO ₃: 0.01g/L; Na ₂moO ₄: 0.025g/L; NiCl ₂6H ₂o:0.024g/L; Na ₂wO ₄2H ₂o:0.024g/L; VITAMIN: 12.5mL/L, consists of vitamins B ₁: 5.0g/L; Vitamins B ₂: 5.0g/L; Vitamins B ₃: 5.0g/L; Vitamins B ₅: 5.0g/L; Vitamins B ₆: 10.0g/L; Vitamins B ₁₁: 2.0g/L; Vitamin H: 2.0g/L; Para-amino benzoic acid: 5.0g/L; Thioctic Acid: 5.0g/L; Nitrilotriacetic acid: 1.5g/L.

5. method according to claim 3, is characterized in that, described MFCs and MECs anolyte composition is: 12.0mM sodium acetate; 5.8mMNH ₄cl; 1.7mMKCl; 17.8mMNaH ₂pO ₄h ₂o; 32.3mMNa ₂hPO ₄; Mineral element: 12.5mL/L, consists of MgSO ₄: 3.0g/L; MnSO ₄h ₂o:0.5g/L; NaCl:1.0g/L; FeSO ₄7H ₂o:0.1g/L; CaCl ₂2H ₂o:0.1g/L; CoCl ₂6H ₂o:0.1g/L; ZnCl ₂: 0.13g/L; CuSO ₄5H ₂o:0.01g/L; KAl (SO ₄) ₂12H ₂o:0.01g/L; H ₃bO ₃: 0.01g/L; Na ₂moO ₄: 0.025g/L; NiCl ₂6H ₂o:0.024g/L; Na ₂wO ₄2H ₂o:0.024g/L; VITAMIN: 12.5mL/L, consists of vitamins B ₁: 5.0g/L; Vitamins B ₂: 5.0g/L; Vitamins B ₃: 5.0g/L; Vitamins B ₅: 5.0g/L; Vitamins B ₆: 10.0g/L; Vitamins B ₁₁: 2.0g/L; Vitamin H: 2.0g/L; Para-amino benzoic acid: 5.0g/L; Thioctic Acid: 5.0g/L; Nitrilotriacetic acid: 1.5g/L.