| The current environmental issues in China are obvious, the shortage of resource caused by environmental pollution also cannot be underestimated. If energy could be produced during the process of pollution treatment, this would be two important direction of human future development. As an advanced technology in the mutual transformation between resource and pollution, Microbial Fuel Cells (MFC) could use a lot of materials as cathode electron receptor like heavy metal; therefore MFC could be applied in metal waste-water treatment and produce electric energy.The present study aimed improve the MFC’s start process, and low rate of heavy metals treatment caused by the unstable and low electricity production Different methods were used on MFC reactors. Both of series and parallel research were used to study the electrical properties of MFC production and removal efficiency of heavy metals. The results are as follows:(1) Accelerating the rate of MFC’s start process by connected in intermittent parallel mode. The control group only produced a low voltage (100 mV or less) when started after 10 days. But the MFC run in intermittent parallel mode reached a maximum voltage of 467 mV in parallel stage. The voltage would drop by the lifting of the parallel, but on the third day the voltage showing a rising trend. and even intermittent The voltage of MFC was stabilized at 170 ± 3 mV after 15 days in the experimental group. Using a batch parallel mode can shorten the start-up time of the MFC used in the present study (different cathode electron acceptor) from 5 to 7 days.(2) Screening three chemistry cathode (KMnO4, K3[Fe(CN)6], K2Cr2O7) with different concentrations and pH. KMnO4 has become the cathode electron acceptor of MFC in the series phase because of its low toxicity and high efficiency of electricity generation. Operating conditions of KMnO4 cathode was further optimize, The voltage of KMnO4-MFC increased with concentration of KMnO4 (concentrations were 0.5,1.0,2.0 g/L, respectively) increasing when pH at 3.(3) Accelerating the process of copper containing wastewater treatment and gain additional power by KMnO4-MFC and Cu-MFC connected in series. The high voltage and power generated by the KMnO4-MFC supplied for the Cu-MFC. The recovery efficiency of Cu2+ can significantly accelerate in series which reached up to 98%, and the recovery efficiency in 24 h reached up to 91.7%. KMnO4-MFC acceleration copper recovery process while obtaining additional power, the maximum output power reached up to 143 mW;(4) Improving the performance of microbial fuel cells (MFCs) by using an intermittent connection period without power output. Electric energy was accumulated in two MFCs containing heavy metal ions copper, zinc, and cadmium as electron acceptors by connection in parallel for several hours. This method successfully achieved highly efficient removal of heavy metal ions. Even when the acolyte was run in sequencing batch mode, the insufficient voltage and power needed to recover heavy metals from the cathode of MFCs can be complemented by the developed method. The average removal ratios of heavy metal ions in sequencing batch mode were 67% after 10 h. When the discharge time was 20 h, the removal ratios of zinc, copper and cadmium were 91.5% ,86.7%, and 83.57%, respectively; the average removal ratio of these ions after 20 h was only 52.1% for the control group. Therefore, the average removal efficiency of heavy metal ions increased by 1.75 times using the electrons stored from the bacteria under the open-circuit conditions in parallel mode. Electrochemical impedance data showed that the anode had lower solution resistance and polarization resistance in the parallel stage than as a single MFC, and capacitance increased with the length of time in parallel. |
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