Research On Purification Performance Of Soil Pollution By Microbial Fuel Cell

A brand new microbial fuel cell (MFC) which conbimed favorable condition for constructing MFC on soil structure with the proper purification for refractory organics on MFC function, was built in soil environent. Through effective coupling of soil MFC producing electricity mechanism and purification mechanism, the way of using MFC to purify the refractory organic in soil was achieved.The performance of soil MFC on refractory organics purification and simultaneous electricity generation was researched, taking hexachlorobenzene (HCB) as the representative refractory organics. The degradation pathway and intermediates of HCB were analyzed.And the influence factors such as external resistance, buffer concentrations and electrode spacing on electricity generation and degradation of soil MFC was also investigated.(1) At the conditions of pH 7 and 40% moisture content of the agriculture soil, the soil MFC was successfully built. During the 56 days experimental period,4 electricity production cycles were formed, and the maximum voltage of 154mV and the internal resistance of 1009.0Ω were provided. HCB removing efficiency in Closed-circuit soil MFC was 53.54%, higher than the Open-circuit soil MFC of 36.08% and the Non-anaerobic sludge Open-circuit soil MFC of 28.88%.The differences showed the obvious advantages of introductions of MFC and anaerobic sludge in improving the purification efficiency for refractory organics in soil. Degradation products of HCB were investigated through GC-MS and the degradation pathway was analyzed to be HCBâ†'PCBâ†'1,2,3,5-TeCBâ†'1,3,5-TCB in both Closed-circuit soil MFC and the Open-circuit soil MFC.(2) The external resistance had important effect on the performance of soil MFC. The output voltage increased when the external resistance started to go up, while the Closed-circuit soil MFC got lower electric current and removal rate. For a long-time running soil MFC, the closer its external resistance to internal resistance, the lager power density could get. In the Closed-circuit soil MFC, the greater buffer concentration, lead to the larger output current and the smaller the resistance. And within a certain range (0.05-0.2M), buffer concentration was a significant positive linear correlation with current generation. The removal rate of HCB increased along with the increasing buffer concentration, but the added of NaCl was not significantly promoting electricity generation of the Closed-circuit soil MFC and degradation of HCB. Electrode spacing had also great effect on current generation and HCB degradation of Closed-circuit soil MFC.With the decreasing of electrode spacing(80mm-140mm), the current generation and degradation of HCB were declined first and then ascended, and the internal resistance was ascended first and then declined. Within a certain range, narrow electrode spacing could increase the electricity generation of Closed-circuit soil MFC and the degradation of HCB. And below this range(60mm), narrow electrode spacing was not conducive to the electricity generation of Closed-circuit soil MFC and the degradation of HCB.From the electron flow mechanism of soil MFC system, the changing of the electronic distribution on the electrode and the co-substrate effect were the important reasons to promote the purification performance of HCB in the Closed-circuit soil MFC.