CN212750932U

CN212750932U - Cathode capable of accelerating chromium reduction and microbial fuel cell reactor

Info

Publication number: CN212750932U
Application number: CN202021090535.XU
Authority: CN
Inventors: 李猛; 莫测辉; 李彦文; 向垒; 冯乃宪; 蔡全英
Original assignee: Jinan University
Current assignee: Jinan University; University of Jinan
Priority date: 2020-06-12
Filing date: 2020-06-12
Publication date: 2021-03-19
Anticipated expiration: 2030-06-12

Abstract

The utility model relates to a cathode and a microbial fuel cell reactor capable of accelerating chromium reduction. The cathode capable of accelerating chromium reduction comprises a cathode body, and a biomass carbon layer and a polypyrrole layer which are sequentially loaded on the cathode body. The cathode provided by the utility model has excellent conductivity, higher charge mobility and excellent electrochemical stability; the utility model provides a can accelerate negative pole microbial fuel cell reactor electricity production power height that chromium reduced, chromium reduction efficiency is high, and output is high, and the operation is high-efficient stable.

Description

Cathode capable of accelerating chromium reduction and microbial fuel cell reactor

Technical Field

The utility model belongs to the field of microbial electrochemistry, in particular to a cathode and a microbial fuel cell reactor capable of accelerating the reduction of chromium.

Background

Microbial fuel cells (Microbial fuel cells) are a new science developed in recent years, and are a new device which converts chemical energy in organic matters into electric energy by using electricity-generating microbes and can remove pollutants. The microbial fuel cell can degrade organic pollutants in a water body, and can also receive electrons generated in the process of degrading organic matters through the anode electrode, the external circuit and the cathode electrode to generate electric energy. As an energy conversion device, compared with a conventional fuel cell, the microbial fuel cell not only can be used for organic matter, but also can obtain biological energy; the battery can reduce toxic heavy metals into low-toxicity heavy metals at the cathode, obviously reduces the toxicity of the heavy metals, has the advantages of simple operation environment, wide anolyte source, high pollutant removal efficiency, recycling and the like, is an electrochemical technology with great prospect, and continuously obtains the attention of broad students.

Currently, the microbial fuel cell has the defects of low output power, incomplete pollutant removal and the like. This is mainly caused by the slow oxidation rate of the substrate by the microorganisms, the reduction of the cathode conductivity by the chromium hydroxide precipitation at the cathode, and the increase of the internal resistance of the battery. In order to enhance the output power of the microbial fuel cell, and the chromium reduction efficiency, related studies, especially, studies on the cathode electrode and the catalyst, have been made.

The influence of the cathode electrode on the performance of the microbial fuel cell is mainly reflected in that: (1) the structure and the material influence the self conductivity of the electrode and the transmission rate of electrons, influence the output power of the battery and further reduce the chromium removal efficiency of the battery; (2) the resistance characteristics of the cathode are also important factors affecting the output power and the dechromization efficiency of the battery, and therefore, excellent conductivity is a problem that must be considered when selecting a cathode material; however, when a carbon material such as graphite, carbon cloth, or carbon paper is directly used as a cathode, the resulting chromium hydroxide is precipitated on the electrode, and the conductivity of the electrode is suppressed, resulting in poor effects. For example, in CN201410481785.9, when hexavalent chromium is treated by using graphite paper, carbon paper or carbon felt as a cathode material, the generated chromium hydroxide will precipitate on the electrode to inhibit the conductivity of the electrode, and the removal efficiency of total chromium is low (as low as 24%).

In order to solve the problem, the cathode can be modified by properly adopting a high-activity catalyst, so that the electrode still has higher conductivity when the surface of the electrode has precipitates, thereby further accelerating the reaction rate. The composite material of biomass carbon and organic polymer is the best choice of cathode catalyst due to excellent conductive capability, simple processing, high charge mobility and excellent electrochemical stability, and is widely popular in the research fields of energy storage and conversion, pollutant degradation and the like.

Disclosure of Invention

The utility model aims to overcome the defects of low output power, incomplete pollutant removal and the like of the existing chromium removal of the microbial fuel cell, and provide a cathode capable of accelerating the reduction of chromium. The utility model provides a compound catalyst is obtained to the negative pole utilizes living beings carbon-layer and polypyrrole layer complex, has outstanding electric conductivity, higher charge mobility and outstanding electrochemistry stability, uses in the two room microbial fuel cell, can improve the electrogenesis power greatly, has strengthened the reduction effect, and chromium reduction efficiency is high, and output is high, moves high-efficiently stably; moreover, the raw materials selected for use by the utility model have wide sources and low price.

Another object of the present invention is to provide a cathode microbial fuel cell reactor capable of accelerating the reduction of chromium.

In order to realize the purpose of the utility model, the utility model adopts the following technical scheme:

a cathode capable of accelerating chromium reduction comprises a cathode body, and a biomass carbon layer and a polypyrrole layer which are sequentially loaded on the cathode body.

The biomass carbon has the advantages of excellent conductivity, simple processing, high charge mobility, excellent electrochemical stability, wide source and low cost.

Polypyrrole is a conductive polymer which is easy to polymerize into a film, has good stability, and the synthetic method is simple and easy to implement.

The inventor of the utility model tries to load a biomass carbon layer on the electrode body to modify the electrode body, but researches show that the biomass carbon modified carbon cloth shows excellent electrochemical capacity, but the deposition after chromium reduction can inhibit the conductive capacity of the electrode; the polypyrrole layer is loaded on the electrode body to modify the electrode body, and although the distribution condition of chromium precipitates can be regulated, the conductivity of the electrode is limited.

The utility model discloses an inventor is through trying to discover many times, load polypyrrole layer again on the basis of load living beings carbon-layer, and the composite catalyst who obtains possesses strong electric conductive property simultaneously and can regulate and control the chromium deposit of negative pole and distribute, has outstanding electric conductivity, higher charge mobility and outstanding electrochemical stability.

When the cathode is applied to the microbial fuel cell for removing chromium, chromium hydroxide can be prevented from precipitating on the cathode, so that the electricity generating power is greatly improved, the reduction effect is enhanced, the chromium reduction efficiency is high, the output power is high, and the running is efficient and stable. Moreover, the raw materials selected for use by the utility model have wide sources and low price.

The carbon cloth has better conductivity and smaller resistance, and is an excellent electrode carrier; preferably, the cathode body is a carbon cloth.

The sludge carbon has wide source and low price, and can realize the waste utilization of resources; preferably, the biomass carbon layer is a sludge carbon layer.

Preferably, the total thickness of the cathode is 0.06-0.1 mm.

Preferably, the thickness of the cathode body is 0.05-0.08 mm.

Preferably, the thickness of the biomass carbon layer is 0.01-0.03 mm.

Preferably, the thickness of the polypyrrole layer is 0.004-0.008 mm.

The utility model provides a can accelerate negative pole accessible of chromium reduction and prepare to carbon cloth is the negative pole body, and the mud carbon-coat is as living beings carbon-coat as the example, and preparation method is as follows:

(1) high-temperature pyrolysis to obtain sludge carbon

Drying the sludge at 50-60 ℃ for 20-24 h;

and then pyrolyzing the dried sludge at the high temperature of 600-900 ℃ for 120-180 min to obtain sludge carbon.

(2) The sludge carbon layer is loaded on the carbon cloth

Soaking the carbon cloth for 45-75 min by using a hydrochloric acid solution (the mass fraction is 37%), then soaking the carbon cloth for 45-75 min by using a sodium hydroxide solution (0.1mol/L), and then soaking the carbon cloth for 60-100 min by using deionized water to remove impurities and organic matters on the surface;

mixing Nafion, sludge carbon and an organic solvent (such as ethanol) to obtain a mixed solution (the dosage ratio of the Nafion, the sludge carbon and the organic solvent is 5-7: 1: 3-4 muL/mg/muL), and then spraying for 3-5 min by using a small spraying pot to obtain the sludge carbon layer.

(3) The polypyrrole layer is loaded on the sludge carbon layer

Carrying out electrodeposition on the carbon cloth loaded with the sludge carbon layer in a mixed solution of pyrrole and sulfuric acid, then soaking the carbon cloth in deionized water for 15-30 min, and carrying out vacuum drying at 45-60 ℃ for 12-18 h to obtain a polypyrrole layer; the concentration of pyrrole in the mixed solution is 0.4-0.6 mol/L, and the concentration of sulfuric acid is 0.1-0.3 mol/L; the molar ratio of pyrrole to sulfuric acid is 0.8-1.2: 1; the current density of the electrodeposition is 0.001-0.004A/cm²(ii) a The time of the electrodeposition is 20-30 min.

The utility model discloses still request protection one kind and can accelerate chromium reduction negative pole microbial fuel cell reactor, cathode chamber and anode chamber that form including the proton exchange membrane interval, the above-mentioned negative pole that can accelerate chromium reduction arranges in the cathode chamber, and the anode chamber is arranged in to the positive pole, and negative pole and positive pole are placed relatively.

The microbial fuel cell reactor can be used for removing hexavalent chromium. The treatment solution (containing hexavalent chromium) to be dechromized is injected into the cathode chamber as catholyte.

The electricity generation and chromium removal process of the microbial fuel cell reactor comprises the following steps: in an anaerobic environment, the electrogenesis microorganisms at the anode oxidize organic matters into protons, electrons and carbon dioxide, the protons diffuse to the cathode through a proton exchange membrane, and the electrons are transferred to the cathode through an external circuit; meanwhile, hexavalent chromium in the cathode chamber obtains electrons to perform reduction reaction with protons to generate trivalent chromium and water, and current is generated.

Preferably, a cathode sampling sample port is arranged on the cathode chamber, and an anode sampling sample port is arranged on the anode chamber.

The cathode sampling sample port and the anode sampling sample port are convenient for sample adding and sampling at any time, and the removal condition and the power generation condition of chromium in the reactor are obtained.

More preferably, the cathode sampling sample injection port is arranged at the top of the cathode chamber; the anode sampling sample adding port is arranged at the top of the anode chamber.

Preferably, an external resistor is connected between the anode and the cathode in series; and the external resistor is connected with a data acquisition unit in parallel.

Preferably, catholyte is injected into the cathode chamber, and the catholyte is a hexavalent chromium solution of a phosphate buffer solution; the anode chamber is filled with anolyte, and the anolyte is sodium acetate solution of phosphate buffer solution.

The concentration of sodium acetate in the anolyte is 0.75g/L, and the initial pH value is 6.8-7.1.

Anodes conventional in the art may be used in the present invention.

Preferably, the anode is a carbon felt.

Preferably, the ratio of the sum of the areas of the cathode and the anode to the sum of the volumes of the cathode chamber and the anode chamber is 1:14cm²/cm³。

Preferably, the cathode is 1/4 the width of the entire cathode compartment from the proton exchange membrane and the anode is 1/4 the width of the entire anode compartment from the proton exchange membrane.

Compared with the prior art, the utility model discloses following beneficial effect has:

the utility model provides a can accelerate negative pole of chromium reduction has outstanding electric conductivity, higher charge mobility and outstanding electrochemical stability.

The utility model provides a can accelerate chromium reduction negative pole microbial fuel cell reactor and produce electric power height, chromium reduction efficiency is high, and output is high, and the operation is high-efficient stable.

Drawings

Fig. 1 is a schematic structural diagram of a dual-chamber microbial fuel cell reactor provided by the present invention;

fig. 2 is a schematic structural diagram of a cathode capable of accelerating chromium reduction according to the present invention;

FIG. 3 is a polarization curve diagram of SC/PPY-1, SC/PPY-2 and SC/PPY-3 as cathodes in examples 1 to 3, respectively;

FIG. 4 is a graph showing power densities of the cathodes of SC/PPY-1, SC/PPY-2 and SC/PPY-3 in examples 1 to 3, respectively;

FIG. 5 is a graph showing the chromium reduction performance of examples 1 to 3 in which SC/PPY-1, SC/PPY-2 and SC/PPY-3 are used as cathodes, respectively;

wherein, 1 is an external resistor; 2 is an anode sampling sample adding port; 3 is an anode; 4 is an anode chamber; 5 is a proton exchange membrane; 6 is a data acquisition unit; 7 is a cathode sampling sample adding port; 8 is a cathode, 801 is an electrode body, 802 is a biological carbon layer, and 803 is a polypyrrole layer; and 10 is a cathode chamber.

Detailed Description

For a more detailed understanding of the principles of operation, specific objects, aspects and advantages of the present invention. The invention is further described by the following figures and specific examples in conjunction with the description. It should be understood that the specific method examples described below are only for illustrating the present invention and are not intended to be limiting. Furthermore, the technical features mentioned in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

It will be understood that when an element is referred to as being "disposed on," "provided with," or "mounted on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. Any modification, equivalent replacement, improvement and the like made on the basis of the utility model can be combined more and are included in the scope of the invention as long as the spirit and principle of the invention are within.

Example 1

Referring to fig. 1, the present embodiment provides a cathode microbial fuel cell reactor capable of accelerating chromium reduction, which includes an external resistor 1(1000 Ω), an anode sampling port 2, an anode electrode 3, an anode chamber 4, a proton exchange membrane 5, a data collector 6(Keithley model 2007), a cathode sampling port 7, a cathode electrode 8, and a cathode chamber 10.

The anode 3 is positioned in the anode chamber 4, the cathode 8 is positioned in the cathode chamber 10, and the two chambers are separated by a proton exchange membrane 5; the proton exchange membrane 5 is arranged between the two chambers, and the two sides of the proton exchange membrane are respectively contacted with anolyte and catholyte; the anode 3 is at 1/4 near the proton exchange membrane 5 in the anode chamber 4 (i.e., the distance from the anode 3 to the proton exchange membrane 5 is 1/4 of the entire width of the anode chamber 4); the cathode 8 is located at 1/4 near the proton exchange membrane 5 in the cathode chamber 10 (i.e. the distance from the cathode 8 to the proton exchange membrane 5 is 1/4 of the width of the entire cathode chamber 10); the anode sampling sample adding port 2 is arranged at the top of the anode chamber 4; the cathode sampling sample adding port 7 is arranged at the top of the cathode chamber 10; the anode 3 and the cathode 8 are connected with an external resistor 1 through leads; the data collector 6 is connected in parallel with the external resistor 1.

The proton exchange membrane is boiled for 1h by hydrogen peroxide (20 wt%), deionized water, sulfuric acid (0.5mol/L) and deionized water respectively; the total effective electrode area of the anode and the cathode is 25cm²。

The cathode 8 (marked as SC/PPY-1, as shown in figure 2) comprises a cathode body 801 (specifically carbon cloth), and a biomass carbon layer 802 (specifically sludge carbon layer) and a polypyrrole layer 803 which are sequentially loaded on the cathode body 801, wherein the total thickness of the cathode 8 is 0.06mm, the thickness of the sludge carbon layer is 0.03mm, and the thickness of the polypyrrole layer is 0.006 mm.

The cathode 8 is prepared by the following process:

(1) pretreatment of electrodes

Soaking a piece of carbon cloth in a 37% hydrochloric acid solution for 60min, taking out the carbon cloth, soaking the carbon cloth in a sodium hydroxide solution for 60min, and finally soaking the carbon cloth in deionized water for 90min to remove organic matters and other impurities on the surface of the electrode.

(2) Preparation of sludge carbon electrode

Drying sludge from a sewage treatment plant in a drying box at 50 ℃ for 24h, then putting the dried sludge in a high-temperature tube furnace for pyrolysis at 800 ℃ for 120min to prepare sludge carbon, uniformly mixing a Nafion solution, the prepared sludge carbon and ethanol in a ratio of 5:1:4 muL/mg/muL, and spraying for 4min by using a small-sized laboratory spray can through a spraying technology.

(3) Electrodeposition of composite cathodes

The carbon cloth sprayed with the sludge carbon is further electrodeposited in an electrochemical environment, the concentration ratio of pyrrole to sulfuric acid in the electrolyte is 0.9:1 (the concentration of pyrrole is 0.4mol/L, the concentration of sulfuric acid is 0.2mol/L), and the current density during electrodeposition is 0.003A/cm²The electrodeposition time was 30 min.

And soaking the carbon cloth subjected to electrodeposition in deionized water for 20min, and drying in a vacuum drying oven at the drying temperature of 55 ℃ for 12h to obtain the cathode capable of accelerating chromium reduction.

Example 2

This example provides a cathode microbial fuel cell reactor (two-chamber microbial fuel cell reactor) capable of accelerating chromium reduction, which has a structure identical to that of example 1 except that the cathode 8 is different.

Specifically, in the present embodiment, the cathode 8 (denoted as SC/PPY-2) includes a cathode body 801 (specifically, a carbon cloth), and a biomass carbon layer 802 (specifically, a sludge carbon layer) and a polypyrrole layer 803 supported on the cathode body 801 in this order, the total thickness of the cathode 8 is 0.08mm, the thickness of the sludge carbon layer is 0.02mm, and the thickness of the polypyrrole layer is 0.008 mm.

The cathode 8 is prepared by the following preparation method:

(1) pretreatment of electrodes

Soaking a piece of carbon cloth in a 37% hydrochloric acid solution for 60min, taking out the carbon cloth, soaking the carbon cloth in a sodium hydroxide solution for 60min, and finally soaking the carbon cloth in deionized water for 120min to remove organic matters and other impurities on the surface of the electrode.

(2) Preparation of sludge carbon electrode

Drying sludge taken from a sewage treatment plant in a drying box at 55 ℃ for 20h, then putting the dried sludge in a high-temperature tubular furnace for pyrolysis at 600 ℃ for 180min to prepare sludge carbon, uniformly mixing a Nafion solution, the prepared sludge carbon and ethanol in a ratio of 7:1:3.5 muL/mg/muL, and spraying for 3min by using a small-sized laboratory spray can through a spraying technology.

(3) Electrodeposition of composite cathodes

The carbon cloth sprayed with the sludge carbon is further electrodeposited in an electrochemical environment, the concentration ratio of pyrrole to sulfuric acid in the electrolyte is 0.8:1 (the concentration of pyrrole is 0.6mol/L, the concentration of sulfuric acid is 0.3mol/L), and the current density during electrodeposition is 0.004A/cm²The electrodeposition time was 25 min.

And soaking the carbon cloth subjected to electrodeposition in deionized water for 20min, and drying in a vacuum drying oven at 60 ℃ for 16h to obtain the cathode capable of accelerating chromium reduction.

Example 3

This example provides a cathode microbial fuel cell reactor capable of accelerating chromium reduction, which has a structure identical to that of example 1 except that the cathode 8 is different.

Specifically, in the present embodiment, the cathode 8 (denoted as SC/PPY-3) includes a cathode body 801 (specifically, a carbon cloth), and a biomass carbon layer 802 (specifically, a sludge carbon layer) and a polypyrrole layer 803 supported on the cathode body 801 in this order, the total thickness of the cathode 8 is 0.10mm, the thickness of the sludge carbon layer is 0.01mm, and the thickness of the polypyrrole layer is 0.04 mm.

The cathode 8 is prepared by the following preparation method:

(1) pretreatment of electrodes

(2) Preparation of sludge carbon electrode

Drying sludge from a sewage treatment plant in a drying box at 60 ℃ for 22h, then putting the drying box in a high-temperature tubular furnace for pyrolysis at 900 ℃ for 160min to prepare sludge carbon, uniformly mixing a Nafion solution, the prepared sludge carbon and ethanol in a ratio of 6:1:3 muL/mg/muL, and spraying for 5min by using a small-sized laboratory spray can through a spraying technology.

(3) Electrodeposition of composite cathodes

The carbon cloth sprayed with the sludge carbon is further electrodeposited in an electrochemical environment, the concentration ratio of pyrrole to sulfuric acid in the electrolyte is 1.2:1 (the concentration of pyrrole is 0.5mol/L, the concentration of sulfuric acid is 0.1mol/L), and the current density during electrodeposition is 0.001A/cm²The electrodeposition time was 20 min.

And soaking the carbon cloth subjected to electrodeposition in deionized water for 20min, and drying in a vacuum drying oven at the drying temperature of 45 ℃ for 18h to obtain the cathode capable of accelerating chromium reduction.

Application performance test of cathode capable of accelerating chromium reduction

(1) Startup of a dual-chamber microbial fuel cell reactor

An anolyte solution of 0.75g/L sodium acetate in 50mmol/L phosphate buffer (pH 7.0) was added to the anode chamber; to each liter of the buffer were added 0.31g of ammonium chloride, 2.452g of hydrated sodium dihydrogen phosphate, 4.576g of disodium hydrogen phosphate and 0.13g of potassium chloride. Adding anolyte and the domesticated sludge into the anode chamber according to the mass ratio of 3.5:1, and flushing nitrogen for 30min to remove oxygen; the sludge is the mixed sludge of an aerobic tank and an anaerobic tank of a sewage treatment plant of Guangzhou city asphalt Kau. The concentration of hexavalent chromium in the cathode chamber was 25 mg/L.

And (3) carrying out intermittent operation under the condition of closed normal temperature, replacing the anolyte when the output voltage of the microbial fuel cell reactor is lower than 50mV, and successfully starting the reactor when the output voltage reaches a stable state.

(2) Electricity generation performance test of microbial fuel cell reactor

After the microbial fuel cell reactor is successfully started, the output voltage of the cell is monitored in real time, when the organic matter substrate is sufficient and the output voltage is maximum, the output voltage of the cell is monitored by changing the external resistance from 10000 omega to 50 omega, and the polarization curve and the power density curve of the cell are obtained as shown in fig. 3 and fig. 4 respectively.

As can be seen from FIG. 3, the maximum open circuit voltages of the microbial fuel cell reactors based on SC/PPY-1, SC/PPY-2 and SC/PPY-3 cathodes (corresponding to examples 1 to 3, respectively) were 0.953V, 0.992V and 0.925V, respectively.

As can be seen from FIG. 4, the maximum power densities of the microbial fuel cell reactors based on SC/PPY-1, SC/PPY-2 and SC/PPY-3 cathodes were 662.5mW/m, respectively²、759.7mW/m²And 536.9mW/m²。

Complete removal time of hexavalent chromium was obtained by periodically testing the catholyte hexavalent chromium concentration, and the chromium removal time of the microbial fuel cell reactors based on the cathodes of each example and comparative example is shown in fig. 5, and the minimum chromium removal time of the microbial fuel cells providing SC/PPY-1, SC/PPY-2, and SC/PPY-3 cathodes based on examples 1-3 was 30h, 27h, and 34h, respectively.

According to the above, when the cathode provided by the embodiments of the present invention is applied to the chromium reduction cathode microbial fuel cell reactor, the power generation efficiency can be greatly improved, the reduction effect is enhanced, the chromium reduction efficiency is high, the output power is high, and the operation is efficient and stable.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be equivalent replacement modes, and all are included in the scope of the present invention.

Claims

1. A cathode capable of accelerating chromium reduction is characterized by comprising a cathode body (801), and a biomass carbon layer (802) and a polypyrrole layer (803) which are sequentially loaded on the cathode body (801).

2. Cathode capable of accelerating chromium reduction according to claim 1, characterized in that the cathode body (801) is a carbon cloth; the biomass carbon layer (802) is a sludge carbon layer.

3. The cathode capable of accelerating chromium reduction according to claim 1, wherein the total thickness of the cathode is 0.06 to 0.1 mm; the thickness of the cathode body (801) is 0.05-0.08 mm; the thickness of the biomass carbon layer (802) is 0.01-0.03 mm; the thickness of the polypyrrole layer (803) is 0.004-0.008 mm.

4. A cathode microbial fuel cell reactor capable of accelerating chromium reduction, which comprises a cathode chamber (10) and an anode chamber (4) which are formed by separating a proton exchange membrane (5), wherein the cathode (8) for accelerating chromium reduction according to any one of claims 1 to 3 is arranged in the cathode chamber (10), the anode (3) is arranged in the anode chamber (4), and the cathode (8) and the anode (3) are oppositely arranged.

5. The cathode microbial fuel cell reactor capable of accelerating chromium reduction according to claim 4, wherein a cathode sampling sample port (7) is provided on the cathode chamber (10), and an anode sampling sample port (2) is provided on the anode chamber (4).

6. The cathode microbial fuel cell reactor capable of accelerating chromium reduction according to claim 4, wherein an external resistor (1) is connected in series between the anode (3) and the cathode (8); and the external resistor (1) is connected with a data acquisition unit (6) in parallel.

7. The cathode microbial fuel cell reactor capable of accelerating chromium reduction according to claim 4, wherein a catholyte is injected in the cathode chamber (10), and the catholyte is a hexavalent chromium solution which is a phosphate buffer solution; an anolyte is injected into the anode chamber (4), and is a sodium acetate solution of a phosphate buffer solution.

8. The cathode microbial fuel cell reactor capable of accelerating chromium reduction according to claim 4, wherein the anode (3) is carbon felt.

9. Cathode microbial fuel cell reactor capable of accelerating chromium reduction according to claim 4 characterized in that the ratio of the sum of the areas of the cathode (8) and anode (3) to the sum of the volumes of cathode chamber (10) and anode chamber (4) is 1:14cm²/cm³。

10. A cathode microbial fuel cell reactor accelerating chromium reduction according to claim 4 wherein the distance from the cathode (8) to the proton exchange membrane (5) is 1/4 of the width of the whole cathode compartment (10) and the distance from the anode (3) to the proton exchange membrane (5) is 1/4 of the width of the whole anode compartment (4).