Energetic evaluation of phenol wastewater treatment by reverse electrodialysis reactor using different anodes

Efficient electrode materials are essential to convert salinity gradient energy into oxidative degradation energy and electrical energy by reverse electrodialysis reactor (REDR). In this context, comparative experiments of REDR using different anodes (Ti/IrO 2 –RuO 2, Ti/PbO 2 and Ti/Ti 4 O 7 ) were conducted. The effects of output current and electrode rinse solution (ERS) flowrate on mineralization efficiency and energy output were discussed. Results demonstrated that the COD removal rate( η COD ) rose almost linearly with output current and ERS flowrate when using Ti/Ti 4 O 7 anode, but excessive operating conditions caused a slow increase or even decrease of η COD when using Ti/IrO 2 –RuO 2 or Ti/PbO 2 anodes. The order of electrode system potential loss ( E ele ) for the three anodes was Ti/Ti 4 O 7 > Ti/PbO 2 > Ti/IrO 2 –RuO 2. High E ele was beneficial to η COD but had a negative effect on the net output power ( P net ) of REDR. Regardless of the applied anodes, increasing the current and decreasing the ERS flowrate was detrimental to P net due to higher E ele. Based on these findings, four energy efficiency parameters were defined to evaluate energy recovery from multiple perspectives by linking energy output with mineralization capacity. They were electrode efficiency ( η ele ), energy efficiency ( EE ), general current efficiency ( GCE ) and energy consumption ( EC ), respectively. Results showed that REDR with Ti/Ti 4 O 7 anodes and suitable operating conditions achieved the optimal energy indicators and mineralization efficiency, which provided an efficient and economical option for wastewater treatment and energy recovery.