Preparation of a new type of composite anode and microbial fuel cell based on nitrogen doped biological carbon and porous volcanic rocks

Abstract

A preparation method for a novel composite anode based on nitrogen-doped charcoal of sludge and porous volcanic, and a microbial fuel cell, relating to the technical field of resource utilization of new materials, new energy and wastewater. Active sludge is prepared into porous nitrogen-doped charcoal by using a nitrogen high-temperature pyrolysis baking method; and then, surface minerals are removed by using an acidification method to improve the electrical conductivity of the charcoal; finally, surface charcoal loading is performed by taking volcanic granules as a carrier to prepare and form nitrogen-doped charcoal granules on a volcanic surface. The novel granules have high porosity, high electrical conductivity and large specific surface area, and fully meet the performance requirement of the anode material of the microbial fuel cell. The anode of the novel nitrogen-doped porous charcoal can increase the loading capacity of electricity-producing bacteria and microorganisms of the anode of the microbial fuel cell, and improve the conversion rate of biomass energy in wastewater; by virtue of low-resistance characteristics, the electron transfer efficiency is also improved, and finally, the power of the microbial fuel cell is enhanced, so that both wastewater treatment and recycling and efficient biological power generation are achieved.

Claims

1. A preparation method of a composite anode doped nitrogen based on biological carbon and porous volcanic rocks, comprising: (1) preparing dry power sludge by drying activated sludge and calcining the activated sludge at 600˜700° C. without oxygen; (2) making porous carbon powder doped with nitrogen by purifying the dry powder sludge by acidification; (3) drying the porous carbon powder doped nitrogen; (4) selecting volcanic rock particles with more than 40% porosity for purge and deionized water cleaning; (5) using PVDF as binder, mixing PVDF and drying the porous carbon powder doped with nitrogen in DMF, and then adding the volcano rock particles, evenly coating the porous carbon powder doped with nitrogen on outer surface of the volcano rock particles after mixing; then calcining them at 600-700° C. without oxygen, inoculating new porous carbon particles doped with nitrogen with Shewanella, which is a composite anode doped with nitrogen based on biochar and porous volcano rocks.

2. A MFC using a composite anode doped with nitrogen based on the biochar and porous volcanic rocks, wherein: biochar doped with nitrogen based on porous volcano rock is filled in an anodic chamber of MFC as electrode, a filling rate is 95-100%; carbon rods are inserted in the composite anode porous biochar doped with nitrogen, and titanium wire on a top of the carbon rods is connected with data collection system; a water inlet is set on a top of the anodic chamber, hydraulic transmission is performed using gravity flow model; a gas check valve is arranged at a top end of an anode chamber; a saturated calomel reference electrode is inserted into the biological carbon, which is connected to an external data collection system; the anode chamber and a cathode chamber are designed from top to bottom, the chambers are separated by nonwoven fabrics; activated carbon is used as air cathode catalyst of the cathode chamber, PVDF membrane is coated on carbon cloths, connecting with the data collection system; an external resistance is connected between the cathode and the anode.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1—The power density and polarization curve of the new type of porous bio carbon doped nitrogen anode of MFC.

(2) In the figure, the abscissa coordinates indicate the current density, the unit is A/m.sup.3. The longitudinal coordinate (Y.sub.left) indicates the cell potential and the unit is V; the ordinate (Y.sub.right) represents the power density, the unit is W/m.sup.3; the square and the triangle represent the polarization curve and the power density curve respectively.

(3) FIG. 2—The cell potential of of the new type of porous bio carbon doped nitrogen anode of MFC.

(4) In the picture, the abscissa coordinates indicate the time, the unit is d, the ordinate represents the electric potential, the unit is V, the square, the dot and the triangle denote the anodic potential, the cathode potential and the battery potential, respectively.

SPECIFIC IMPLEMENTATION METHODS

(5) The specific implementation method of the invention is described in detail in combination with the technical scheme.

(6) The preparation of porous biochar doped nitrogen: 1000 g activated sludge was filtered and dehydrated (filter cake moisture content <50%), and dried in vacuum drying box at constant temperature at 105° C. The drying sample was transferred to a tube furnace, and the nitrogen was inputted but isolated oxygen. The nitrogen entry rate was 300 mL/min, the heating rate was 5° C./min, the temperature was set at 700° C., and the baking time was set to 1 h.

(7) Porous biological carbon doped Nitrogen acidification: bio carbon powder doped nitrogen was mixed with 200 mL hydrofluoric acid (concentration: 50%) and stirred 1 h in magnetic stirrer. The acidified biochar solution was statically sinked 3 h and removed the supernatant. Deionized water was used to clean the biological carbon for some times until neutral (pH=7). The acidified biological carbon was transferred to the vacuum drying box, and dried for 12 h at constant 60° C. After drying, the sample was transferred to a dry dish to be sealed and reserved.

(8) Preparation of porous biochar particles doped nitrogen: 500 g 3-5 mm volcanic rock particles were screened and immersed in deionized water, and then oscillated by ultrasound for 2 h to remove surface dust and impurities, washed 3 times using deionized water. After cleaning, the volcanic rocks were dried at 60° C. in the vacuum drying box for 3 h at constant temperature. The 5% acidified biological carbon powder was stirred with 10% PVDF using DMF as the solvent, and the stirring time was 1 h, and the biological carbon coated solution was made.

(9) With volcanic particles as the core, the particles of volcanic rock were placed in the biofilm solution to stir and hang up the membrane. The uniform particles were taken out and placed in air for 20 s. The phase transformation time was 3 h. The volcanic rocks coated carbon were transferred to the vacuum drying box, and the drying time was 3 h at 105° C. After drying, the biochar particles were transferred to the tube furnace again, and the nitrogen was pumped but isolated oxygen. The nitrogen entry rate was 300 mL/min, the heating rate was 5° C./min, the setting temperature was 700° C., and the baking time was set to 1 h.

(10) MFC assembly: the design size of anode chamber was φ100×100 mm, filled with new porous biochar particles doped nitrogen as anode microorganism filler, and the filling rate was 95%. 6 mm diameter carbon rod was setted in the center of anode chamber, titanium wire on the top of the carbon rod was drawed out the chamber, calomel reference electrode was inserted at the top of the anode chamber, titanium wire and reference electrode were respectively connected to the data collection system. A gas check valve was integrated in the top seal plate of anode chamber.

(11) The anode chamber was connected to the cathode chamber using non-woven fabric as separator. The design size of cathode chamber was φ100×30 mm, filled with activated carbon as cathode catalyst (filling rate: 100%). Carbon fiber cathode was arranged at the bottom of cathodic chamber as air cathode. The carbon fiber wire was used to connect with the data collection system, 1000Ω external resistance was setted between titanium wire and cathode carbon fiber. The anode chamber was inflowed on the top and flowed from the bottom of the anode chamber.

(12) Device performance tests: the anode chamber was inoculated with Shewanella electricigens. The wastewater was transported into the anode chamber through the peristaltic pump. After the anode potential was stable, the system was debugged.

(13) After the battery potential was stable, the polarization curve and the power density curve were tested. As shown in FIG. 1 and FIG. 2, the performance test results indicated that the device could significantly improve the cell potential and coulombic efficiency.