Mechanism And Application Of Cr(Ⅵ) Removal In Mfcs Cathode

Hexavalent chromium Cr(Ⅵ)is a toxic heavy metal in industrial wastewater,and its harm to the environment and mankind has become an urgent problem.In recent years,microbial fuel cell(MFC)become a new method of hexavalent chromium pollution water bioremediation,due to it can reduce Cr(Ⅵ)to trivalent chromium(Cr(III))directly,high efficiency and no secondary pollution.In this study,we isolated the Cr(Ⅵ)resistant strains from an outlet in Lanzhou section of the Yellow River,and chose the strains which has high Cr(Ⅵ)reduction rate building a microbial fuel cell biocathode to promote Cr(Ⅵ)reduction.Meanwhile we apply the sediment microbial fuel cell(SMF)using Cr(Ⅵ)as electron acceptor in cathode to achieve the organic matter in sediment removal and Cr(Ⅵ)in water removal simultaneously.The results show that 21 strains with Cr(Ⅵ)reducing ability were isolated and purified.The LZU-26 strain can reduce 95.89% of Cr(Ⅵ)after 24 h and 99.97% of Cr(Ⅵ)after 48 h at the initial Cr(Ⅵ)concentration of 0.4 mmol/L,respectively.Furthermore,applying LZU-26 to microbial fuel cell biological cathode,the maximum voltage is 68 mV and the Cr(Ⅵ)reduction rate of biological cathode(68.9%)was higher than that of chemical cathode(14.7%)and control group(2.7%).In other hands,the maximum voltage of the sediment fuel cell with Cr(Ⅵ)can reach 110 mV.The total organic carbon(TOC)removal of three groups(SMFC with Cr(Ⅵ),SMFC without Cr(Ⅵ)and open circuit SMFC)were 30.07%,13.74%,7.84%.It confirmed that the sediment TOC removal rate increased 2.18 times by Cr(Ⅵ)as electron acceptor.SMFCs,Cr(Ⅵ)as electron acceptor,have been running for 48 days(4 cycles).During the operation time,the Cr(Ⅵ)reduction rate and the power generation capacity were stable.The results of the MiSeq sequencing show that the operation of the sediment cell largely reduces the bacterial diversity.In the sediment microbial fuel cell(SMFC)anode biofilm,Bacteroidetes accounted for 42.9% of total composition,the next are Proteobacteria(33.6%),Chloroflexi(7.5%),Euryarchaeota(7.5%),Firmicutes(3.3%),Spirochaetes(2.5%).Therefore,the sediment microbial fuel cell(SMFC)and MFC biocathode treat of chromium-containing wastewater will be an efficient,energy-saving and environmentally friendly method.