CN104480493B - Method for recycling copper and cadmium and preparing cadmium bronze precursor employing compact biological electrochemical reactor - Google Patents

Abstract

The invention provides a compact bioelectrochemical reactor for recovering copper and cadmium and preparing a cadmium bronze precursor, which belongs to the technical field of bioelectrochemistry. The bioelectrochemical reactor is switched to microbial fuel cell or microbial electrolytic cell mode through a relay switch; in the microbial fuel cell mode, the external resistance is connected in series; in the microbial electrolytic cell mode, a small resistance is connected in series, and an external power supply is connected; The chamber is filled with a mixed salt solution of Cu(II) and Cd(II); the cathode and anode of the reactor are conductive carbon materials; the anode chamber of the reactor is inoculated with the clarifier sludge of the sewage treatment plant as electrochemically active microorganisms. The process of the invention is clean and efficient, the reactor is compact, the structure is simple, and the operation is convenient, and it has good application prospects for the treatment of copper and cadmium wastewater and the preparation of cadmium bronze precursor.

Description

A compact bioelectrochemical reactor for recovery of copper and cadmium and preparation of cadmium bronze precursors Methods

technical field

The invention belongs to the technical field of bioelectrochemistry, uses microbial fuel cells (MFCs) to selectively separate and recycle copper from copper-cadmium wastewater; and switches the MFCs to the microbial electrolysis cell (MECs) mode without changing the main body of the reactor , and further recover the metal cadmium in the above wastewater, which has the characteristics of compact reactor structure and convenient operation. Based on the catalysis of copper recovery in MFCs mode, the system utilizes copper in situ and realizes efficient recovery of cadmium. The resulting copper-cadmium complex is the precursor and raw material for preparing cadmium bronze with good electrical and thermal conductivity.

Background technique

Heavy metal copper and cadmium are widely used in many fields of industrial production, such as alloys, electroplating, neutron absorption control rods, pigments, plastic stabilizers, phosphors, insecticides, fungicides, and paints. Therefore, copper and cadmium heavy metal wastewater treatment has always been one of the focuses of attention. At present, there are more than 20 patents on the treatment and recovery of wastewater containing copper and cadmium. These methods mainly include chemical precipitation, adsorption, ion exchange, iron oxidation and electrochemical methods. For example, patents CN201310533532, CN201310615806, CN201410111803, etc. The disadvantages of these methods are mainly the large amount of treatment agent used, the reaction is not easy to control, easy to cause secondary pollution, high cost, difficult to recover metals, and high energy consumption. Finding new methods for copper and cadmium recovery that are clean, efficient, and energy-free/low-energy is an inevitable requirement for sustainable social development.

Cadmium bronze is a metal material with high electrical properties, thermal conductivity, and good wear resistance. It is one of the important non-ferrous metal materials used in the defense industry. The production of cadmium bronze is generally made of cadmium copper alloy, which is smelted by selecting a certain solution treatment temperature and time in a high-frequency electric furnace. If a clean and effective method can be selected to recover the valuable metals copper and cadmium in the copper-cadmium wastewater and prepare the precursor of the cadmium bronze, the resource utilization of the copper-cadmium wastewater can be realized.

The bioelectrochemical system is a new technology emerging in recent years. When the chemical reaction between the anode and the cathode can proceed spontaneously, the system is MFCs; when a small voltage needs to be applied from the outside to make the anode and cathode reaction proceed, the system is MECs. With the development and deepening of research and development, the application fields of MFCs and MECs have been expanded. As far as 35 MECs and 543 MFCs patents have been published or authorized at home and abroad, the research goals have changed from simple organic wastewater treatment and hydrogen production (WO2014082989, CN201310627011, CN201410209650, CN201310148645, CN201210369997) to _CO2 fixation (CN201110209149, CN201410169707)、脱氮脱盐(WO2010124079、CN201210550133)、生产甲烷(CN201210240982)、传感与监测(CN201410298473、CN201310226890、CN201310214163)、污染场地修复(CN201420151230)、有机产品制备(US2013256149、CN201310212120)、钴和镍等Single metal leaching and recovery (CN201310345579, CN201210153753, CN201210153753, CN201310145779) and so on. As far as bioelectrochemical treatment and recovery of mixed metal wastewater is concerned, research and development work is relatively rare and limited to the recovery of copper, lead, cadmium, and zinc by MECs with different applied voltages (Modin O, Wang X, Wu X, Rauch S, Fedje et al. KK. Bioelectrochemical recovery of Cu, Pb, Cd, and Zn from dilute solutions. J Hazard Mater 2012, 235-236: 291-297). Our research group has also developed MFCs to drive MECs to recover chromium, copper and cadmium (CN201410175987), and Cu(II) to promote the leaching of Co(III) (201310071793.1). Completely different from the above-mentioned research ideas, research content and principles, research objectives and problems to be solved, the present invention cleverly realizes the switching and Function conversion, while saving reactor and site space, utilizes the underpotential deposition cadmium effect of copper recovery in MFCs mode to realize efficient recovery of cadmium and preparation of cadmium bronze precursor in MECs mode.

Contents of the invention

The invention provides a method with clean process, compact reactor structure, convenient operation, copper and cadmium waste water treatment, simultaneous recovery of copper and cadmium and preparation of cadmium bronze precursor.

The technical scheme adopted in the present invention is as follows: a method for reclaiming copper and cadmium in a compact bioelectrochemical reactor and preparing a cadmium bronze precursor, the specific steps are as follows:

The relay switch is controlled by the time electromagnetic relay to switch the bioelectrochemical reactor to the microbial fuel cell or microbial electrolytic cell mode;

When the bioelectrochemical reactor is in MFCs mode, connect an external resistance of 100-500Ω in series;

When the bioelectrochemical reactor is in the MECs mode, connect a 5-50Ω resistor in series and an external power supply of 0.5-1.0V;

The cathode compartment of the bioelectrochemical reactor is filled with a mixed salt solution of Cu(II) and Cd(II), and the cathode and anode electrodes of the bioelectrochemical reactor are conductive carbon materials;

The anode compartment of the bioelectrochemical reactor is filled with electrochemically active microorganisms and anolyte;

The anode compartment of the bioelectrochemical reactor was inoculated with clarifier sludge from a sewage treatment plant as electrochemically active microorganisms.

The mixed salt solution of Cu(II) and Cd(II) is a mixed salt solution of copper sulfate and cadmium sulfate, a mixed solution of copper sulfate and cadmium chloride, a mixed salt solution of copper chloride and cadmium sulfate, A mixture of copper and cadmium chloride.

The carbon material is carbon cloth, carbon rod or carbon felt.

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

The composition of the anolyte 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 ; 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 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, composed of 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 _B11 : 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 and the cathode chamber of the reactor of the present invention need to maintain an oxygen-free environment during operation, and anaerobic conditions can be realized by feeding nitrogen.

The process flow of the reactor operation 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, since the standard redox potentials of Cu(II) and Cd(II) are +0.52 V and –0.40 V, respectively, the Cu(II) and Cd(II) adsorbed on the electrode will flow in MFCs and MECs, respectively. mode is selectively reduced to elemental copper or cadmium.

The process flow of the operating stage for improving the recovery rate of cadmium in MECs of the present invention is as follows: Cu(II) is reduced to simple substances in MFCs mode. According to the underpotential deposition cadmium effect of copper, the copper-plated electrode catalyzes and efficiently recovers cadmium in the MECs mode, and simultaneously prepares the cadmium bronze precursor.

Description of drawings

Figure 1 is a schematic diagram of a bioelectrochemical reactor for recovering copper and cadmium and preparing cadmium bronze precursor.

Fig. 2 is the variation of Cu(II), Cd(II) recovery rate over time under the MFCs mode of embodiment 1.

Fig. 3 is the Cd (II) recovery rate and the hydrogen yield of the MECs mode operation 4h of embodiment 1, and the contrast of non-copper-plated electrode.

Fig. 4 is the current density under the MECs mode of embodiment 1, and the contrast of non-copper plated electrode.

Fig. 5 is the cyclic voltammetry curve in the MECs mode of Example 1, and the comparison of non-copper-plated electrodes, no copper-plated electrodes-no Cd(II), and copper-plated electrodes-no Cd(II).

In the figure: 1 carbon rod; 2 reference electrode; 3 carbon cloth; 4 hydrogen collection tube; 5 cathode mixture;

6 cation exchange membrane; 7 anode chamber; 8 cathode chamber; 9 power supply; external resistance in 10MFCs mode;

11 Resistor in MECs mode; 12 Time electromagnetic relay; 13 In and out sample port.

detailed description

The specific implementation manners of the present invention will be further described below in conjunction with the accompanying drawings and technical solutions.

Example 1

Step 1: Build the reactor, as shown in Figure 1: the anode chamber 7 and the cathode chamber 8 of the reactor are made of plexiglass, the volume of the solution in the anode chamber is 15mL, and the volume of the solution in the cathode chamber is 25mL, and the ion exchange membrane (CMI-7000) 6 separated, 200Ω external resistance 10 in series in MFCs mode, 10Ω resistance 11 in series in MECs mode and 0.5V voltage applied.

Step 2: Place the reactor anode electrode (carbon rod and carbon felt) and cathode electrode (carbon cloth) in the reactor anode chamber 7 and cathode chamber 8 respectively. The apparent size of the carbon rod (Beijing Sanye Carbon Material Co., Ltd.) is , carbon felt (Beijing Sanye Carbon Materials Co., Ltd.) with an apparent size of 3.0cm×2.0cm×1.0cm). The reference electrode 2 is connected to the cathode chamber of the reactor, and the voltage across the resistor 11 is collected through the computer and the data acquisition system and the current is calculated; the cathode potential of the reactor is collected according to the reference electrode.

Step 3: Add 15mL of culture solution to the anode chamber of the reactor, 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 ; 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 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 4: Add 25 mL of deionized water to the cathode chamber of the reactor.

Step 5: Close the main switch of the circuit, and place the switch of the electromagnetic relay in the MFCs mode. The device was brought to room temperature (20-25°C) for acclimation and operation. When the current drops below 0.02mA, one cycle is completed, and the above-mentioned medium components are added. Five consecutive cycles of domestication and enrichment of anodic electrochemically active bacteria.

Step 6: Replace the cathode deionized water in step 4 with a mixture of 100 mg/L CuSO ₄ and 50 mg/L CdSO ₄ , the medium is 0.1M sodium acetate-acetic acid buffer solution (pH=4.6), and aerate with nitrogen for 20 minutes.

Step 7: Place the electromagnetic relay switch in the MFCs mode, take samples regularly, analyze the Cu(II) and Cd(II) content in the liquid phase, and calculate the recovery rate.

Step 8: Copper is basically recovered when the MFCs mode is operated for 21 hours, and the electromagnetic relay switch is placed in the MECs mode, and samples are taken regularly to analyze the Cd(II) in the liquid phase and the hydrogen content in the gas phase.

Step 9: Characterize the cyclic voltammetry curves of the copper-plated electrode in MECs mode, the blank electrode without copper plating, and the control with or without Cd(II); calculate the cathode Coulombic efficiency, external electric energy efficiency, and total system efficiency based on cadmium and hydrogen in MECs mode. Energy efficiency, cadmium yield, hydrogen yield.

The following table is the cathode coulombic efficiency, external electric energy efficiency, total system energy efficiency, cadmium yield, and hydrogen yield based on cadmium and hydrogen in the MECs mode of Example 1.

In this example, copper and cadmium are recovered and a cadmium bronze precursor with a certain composition is prepared. The reactions that occur at the cathode in the MFCs mode are formula (1), and the reactions at the cathode in the MECs mode are formulas (2) and (3). In MECs mode, cathode coulombic efficiency based on cadmium (CE _Cd ), cathode coulombic efficiency based on hydrogen (CE _H2 ), external electric energy efficiency (η _E,Cd ,η _E,H2 ), total system energy efficiency (η _E+S, The calculations of _Cd ,η _E+S,H2 ), cadmium yield (Y _Cd ), and hydrogen yield (Y _H2 ) are shown in formulas (4)-(11).

Cu ²⁺ +2e ^- → Cu(s) (1)

Cd ²⁺ +2e ^- →Cd(s) (2)

2H ⁺ +2e ^- →H ₂ (g) (3)

${\mathrm{<span\; class="notranslate">\; CE</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 96485</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&Delta;C</span>}}_{{\mathrm{<span\; class="notranslate">\; CD</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; a</span>}}}{\mathrm{<span\; class="notranslate">\; 1000</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; \&times;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}\mathrm{<span\; class="notranslate">\; \%</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; CE</span>}}_{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 96485</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}\mathrm{<span\; class="notranslate">\; \%</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 96485</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&Delta;C</span>}}_{{\mathrm{<span\; class="notranslate">\; CD</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{{\mathrm{<span\; class="notranslate">\; CD</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>}}}{\mathrm{<span\; class="notranslate">\; 1000</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; \&times;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}\mathrm{<span\; class="notranslate">\; \%</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&Delta;H</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; \&times;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}\mathrm{<span\; class="notranslate">\; \%</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 96485</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&Delta;C</span>}}_{{\mathrm{<span\; class="notranslate">\; CD</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{{\mathrm{<span\; class="notranslate">\; CD</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>}}}{\mathrm{<span\; class="notranslate">\; 1000</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; \&times;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}\mathrm{<span\; class="notranslate">\; \%</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; \&Delta;H</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; \&times;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}\mathrm{<span\; class="notranslate">\; \%</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&Delta;C</span>}}_{{\mathrm{<span\; class="notranslate">\; CD</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; a</span>}}}{\mathrm{<span\; class="notranslate">\; 1000</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{{\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{{\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

In the MECs mode, the change value (mg/L) of the cadmium ion concentration in the initial and final states of the reaction, b ₁ and b ₂ are the number of electrons required to reduce a unit of cadmium and generate a unit of hydrogen, respectively; V _ca and _Van are the reactor The cathode and anolyte volumes (L); E _Cd2+ is the theoretical reduction electrode potential (V) of Cd(II) under experimental conditions, E _ap is the applied voltage (V), n _H2 and n _S are the reaction from the beginning to the end, respectively The amount of substance in state hydrogen, the amount of substance (mol) consumed by the anode substrate, G _S is the Gibbs free energy (J/mol) of sodium acetate oxidation under experimental conditions, ΔH _{S, H2} is the combustion heat of hydrogen ( J/mol), the change value of chemical oxygen demand in the anode of the ΔCOD reactor (g/L), I is the current in the circuit (A), t is the running time of the reactor (s), M _Cd and M _O2 are elemental The relative molecules of cadmium and oxygen (g/mol), 96485 is Faraday's constant, (C/mol e ^- ); 1000 is the dimension conversion unit (mg/g).

Results: With the prolongation of the operation time of the reactor in MFCs mode, the recovery rate of Cu(II) increased continuously, and the recovery rate of Cu(II) in 21h reached 96.8±1.6% (Fig. 2); while the Cd(II) recovery rate in the whole process ) (10.6 ± 1.3% (Fig. 2)) was mainly attributed to the adsorption of the electrodes. When the reactor was switched to MECs mode, the recovery rate of Cd(II) was 46.6±1.3% at 4h (Figure 3); while the comparison experiment of non-copper-coated cathode under the same conditions showed that the recovery rate of Cd(II) was only 26.1% ±1.1% (Figure 3), so the cadmium recovery efficiency of the copper-plated electrode has increased by 78.5%. The current densities under copper-plated and non-copper-plated electrode conditions were 1.52±0.09A/m ² and 0.31±0.01A/m ² (Figure 4), indicating that copper deposited in MFCs mode promotes Recovery and reduction of Cd(II). Cyclic voltammetry analysis (Figure 5) shows that the reduction peak potentials of cadmium in copper-plated and non-copper-plated cathodes in MECs mode appear at –0.57V and –0.61V, respectively, and the potential of the former is positive compared with the latter, indicating that the electrode surface The generated copper has a catalytic effect on the subsequent reduction of Cd(II); correspondingly, the reduction peak current of cadmium on the copper-plated electrode is also larger, indicating that the copper generated in the MFCs mode accelerates the electrode reaction speed in the MECs mode.

In the MECs mode (above table), compared with the non-copper-coated control electrode, the total system energy efficiency and cadmium yield of the copper-coated electrode are both increased; while the cadmium-based cathode Coulombic efficiency and the external electric energy efficiency are lower; based on The cathode coulombic efficiency of hydrogen, the efficiency of external electric energy, the total energy efficiency of the system and the yield of hydrogen all increase. These results indicate that the reduction efficiency of cadmium at the cathode is enhanced after copper plating, and the evolution of hydrogen gas is also increased, and the hydrogen production competes for the reduction of cadmium.

In summary, MFCs were used to selectively separate and recover copper from copper-cadmium wastewater, and the recovery rate of Cu(II) reached 96.8±1.6%. On the premise of not changing the main body of the reactor, the MFCs were switched to the MECs mode for further recovery Metallic cadmium in wastewater. Compared with the blank without copper plating on the electrode, the recovery rate of Cd(II) was increased by 78.5% on the copper-coated electrode, thus realizing the in-situ catalysis of copper recovery in MFCs mode and the efficient recovery of Cd(II) in MECs mode. The ratio of copper and cadmium in the prepared cadmium bronze precursor is 4.16±0.07g/g. By controlling the amount of Cd(II) reduction in the MECs mode through a time electromagnetic relay, the content of cadmium in the copper-cadmium product can be further adjusted, and cadmium bronze precursors with different proportions can be prepared according to the needs. The process is clean and pollution-free, and has both environmental and ecological benefits, social benefits and economic benefits.

Claims (8)

1. a kind of compact bio-electrochemical reactor reclaim copper, cadmium and prepare cadmium bronze precursor method it is characterised in that

Relay switch is controlled by time electromagnetic relay, bio-electrochemical reactor is switched to microbiological fuel cell or micro- Biological electrolysis pool mode；

When bio-electrochemical reactor is in mfcs pattern, the extrernal resistance of series connection 100-500 ω；

When bio-electrochemical reactor is in mecs pattern, the resistance of series connection 5-50 ω, and external power supply 0.5-1.0v；

The cathode chamber of bio-electrochemical reactor loads the mixing salt solution of cu (ii) and cd (ii), bio-electrochemical reactor Negative electrode and anode electrode are conductive material with carbon element；

Equipped with electro-chemical activity microorganism and anolyte in the anode chamber of bio-electrochemical reactor；

The anode chamber of bio-electrochemical reactor is inoculated the depositing reservoir mud of sewage treatment plant as electro-chemical activity microorganism.

2. method according to claim 1 is it is characterised in that the mixing salt solution of described cu (ii) and cd (ii) is sulfur The mixing salt solution of the mixed liquor of the mixing salt solution of sour copper and cadmium sulfate, copper sulfate and Caddy (Cleary), copper chloride and cadmium sulfate, chlorine Change the mixed liquor of copper and Caddy (Cleary).

3. method according to claim 1 and 2 is it is characterised in that described material with carbon element is carbon cloth, carbon-point or carbon felt.

4. method according to claim 1 and 2 is it is characterised in that described depositing reservoir mud ph:6.8-7.0；Electrical conductivity: 0.80-0.93ms/cm；Suspension solid content: 30-35g/l；COD: 150-300mg/l.

5. method according to claim 3 is it is characterised in that described depositing reservoir mud ph:6.8-7.0；Electrical conductivity: 0.80-0.93ms/cm；Suspension solid content: 30-35g/l；COD: 150-300mg/l.

6. the method according to claim 1,2 or 5 is it is characterised in that described anolyte composition is: 12.0mm acetic acid Sodium；5.8mm nh₄cl；1.7mm kcl；17.8mm nah₂po₄·h₂o；32.3mm na₂hpo₄；Mineral element: 12.5ml/l, Consist of mgso₄:3.0g/l；mnso₄·h₂o:0.5g/l；nacl:1.0g/l；feso₄·7h₂o:0.1g/l；cacl₂· 2h₂o:0.1g/l；cocl₂·6h₂o:0.1g/l；zncl₂:0.13g/l；cuso₄·5h₂o:0.01g/l；kal(so₄)₂· 12h₂o:0.01g/l；h₃bo₃:0.01g/l；na₂moo₄:0.025g/l；nicl₂·6h₂o:0.024g/l；na₂wo₄·2h₂o: 0.024g/l；Vitamin: 12.5ml/l, consists of vitamin b₁:5.0g/l；Vitamin b₂:5.0g/l；Vitamin b₃:5.0g/ l；Vitamin b₅:5.0g/l；Vitamin b₆:10.0g/l；Vitamin b₁₁:2.0g/l；W factor: 2.0g/l；P-aminophenyl first Acid: 5.0g/l；Thioctic acid: 5.0g/l；Aminotriacetic acid: 1.5g/l.

7. method according to claim 3 is it is characterised in that described anolyte composition is: 12.0mm sodium acetate； 5.8mm nh₄cl；1.7mm kcl；17.8mm nah₂po₄·h₂o；32.3mm na₂hpo₄；Mineral element: 12.5ml/l, composition For mgso₄:3.0g/l；mnso₄·h₂o:0.5g/l；nacl:1.0g/l；feso₄·7h₂o:0.1g/l；cacl₂·2h₂o: 0.1g/l；cocl₂·6h₂o:0.1g/l；zncl₂:0.13g/l；cuso₄·5h₂o:0.01g/l；kal(so₄)₂·12h₂o: 0.01g/l；h₃bo₃:0.01g/l；na₂moo₄:0.025g/l；nicl₂·6h₂o:0.024g/l；na₂wo₄·2h₂o:0.024g/ l；Vitamin: 12.5ml/l, consists of vitamin b₁:5.0g/l；Vitamin b₂:5.0g/l；Vitamin b₃:5.0g/l；Vitamin b₅:5.0g/l；Vitamin b₆:10.0g/l；Vitamin b₁₁:2.0g/l；W factor: 2.0g/l；Para-amino benzoic acid: 5.0g/ l；Thioctic acid: 5.0g/l；Aminotriacetic acid: 1.5g/l.

8. method according to claim 4 is it is characterised in that described anolyte composition is: 12.0mm sodium acetate； 5.8mm nh₄cl；1.7mm kcl；17.8mm nah₂po₄·h₂o；32.3mm na₂hpo₄；Mineral element: 12.5ml/l, composition For mgso₄:3.0g/l；mnso₄·h₂o:0.5g/l；nacl:1.0g/l；feso₄·7h₂o:0.1g/l；cacl₂·2h₂o: 0.1g/l；cocl₂·6h₂o:0.1g/l；zncl₂:0.13g/l；cuso₄·5h₂o:0.01g/l；kal(so₄)₂·12h₂o: 0.01g/l；h₃bo₃:0.01g/l；na₂moo₄:0.025g/l；nicl₂·6h₂o:0.024g/l；na₂wo₄·2h₂o:0.024g/ l；Vitamin: 12.5ml/l, consists of vitamin b₁:5.0g/l；Vitamin b₂:5.0g/l；Vitamin b₃:5.0g/l；Vitamin b₅:5.0g/l；Vitamin b₆:10.0g/l；Vitamin b₁₁:2.0g/l；W factor: 2.0g/l；Para-amino benzoic acid: 5.0g/ l；Thioctic acid: 5.0g/l；Aminotriacetic acid: 1.5g/l.