| In recent years, energy shortage and environmental pollution have become two crisises which our society must face with and they also seriously restrict human beings improvement and development. Microbial Fuel Cells (MFCs) are a kind of device that can convert the chemical energy (organic contaminants) to electrical energy with the help of bacteria on the anode. Because they can remit the problems of energy shortage and environmental pollution, so they are a kind of potential technology.However, higher operating cost and lower power density are two problems which limit the development of MFCs. To utilize the low grade electrical power, the researchers are developing MFC couple technology which was a hot research topic. In this work, electrosorption driven by MFC (MFC-Sorption) was studied for treatment of wastewater containing phenol and copper heavy metal. And this study also proclaimed the key effect factors and kinetics behhavior of couple technology. It provided a low-energy and high-efficiency method for the treatment of wastewater containing refractory and toxic substances.Firstly, the concentration of eletrolyte, pH of solution, the adsorption systems, the initial concentration of phenol and the number of MFCs in series and in parallel were investigated in phenol wastewater treatment by MFC-Sorption, and then the isotherms and kinetics were studied, and finally the other phenolic compounds treatment in MFC-Sorption system were also explored. The results indicated that the MFC-Sorption system can simultaneously achieve the phenolic compounds treatment and the organics remove without external electrical energy. The main conclutions were as following:1. By using this energy sustainable MFC-Sorption system, the adsorption capacity for100mg/L phenol reached1.70mmol/g, which increased by41.7%compared with the conventional adsorption and was close to electrosorption (1.81mmol/g) that needed external power supply. With the increase of initial phenol concentrations, adsorption capacity of phenol on ACFs electrode increased, but removal efficiency of phenol decreased. It proved that high electrolyte concentration and low solution pH promoted the performance of phenol removal.2. The adsorption capacity of phenol in MFC-Sorption increased with the increase of the number of MFCs in series and in parallel. And the performance of connection in series was better than that in parallel.3connections in series and in parallel achieved adsorption capacity of1.76mmol/g and1.46mmol/g, respectively, which was much higher than that single MFC (1.25mmol/g).3. The adsorption, electrosorption and MFC-Sorption can be well fitted with Langmuir isotherm, and the maximum adsorption capacity by MFC-Sorption and electrosorption was observed48%and65%higher than that by conventional adsorption. The phenol removal by MFC-Sorption was supposed to be more suitable for a pseudo-second-order kinetics, and with the increase of initial phenol concentration from20mg/L to300mg/L, the initial adsorption rate increased26-fold.4. The performance of p-nitrophenol and2,4-dichlorophenol in MFC-Sorption was better the that of adsorption, suggesting that it was effective in treatment of wastewater containing phenolic compound.Secondly, the concentration of eletrolyte, pH of solution, the electrode metial, the initial concentration of Cu2+and the number of MFCs in series were investigated for Cu2+adsorption. Simultaneously the isotherms and kinetics of copper wastewater adsorption were also studied. And the mechanism of the copper wastewater in MFC-Sorption system was explored. The conclusions were as following:1. A low electrolyte concentration and high solution pH promoted the performance of copper removal. With the increase of initial copper concentrations, the adsorption capacity of copper on ACFs electrode increased, but the removal efficiency of copper decreased.2. When3MFCs connected in series, the adsorption capacity of copper on ACFs electrode was0.468mmol/g, while the adsorption capacity was0.395mmol/g in single MFC system.3. The material of electrode is an important factor in the copper treatment. The Cu removal with Fe and nickel foam as andoe of MFC-Sorption system was better than that of the ACFs, while the stainless steel as the anode was the worst. When graphite felt and modified graphite felt were used as the cathode of MFC-Sorption, the adsorption performance was worse than that of ACFs cathode. In addition, the characterization of ACFs electrode by SEM, EDS and XRD confirmed that Cu and Cu2O were deposited on the surface of MFC-Sorption system electrode, suggesting that MFC-Sorption was not only an adsorption but also a Cu reduction process. MFC-Sorption can simultaneously achieve copper wastewater treatment and organic wastewater treatment (MFC) without an external electrical energy. |
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