Energy recovery and electrode regeneration under different charge/discharge conditions in membrane capacitive deionization

Membrane capacitive deionization (MCDI) is a potential desalination technology, in which part of energy consumed during charge cycle is stored inside electrodes and can be recovered in discharge cycle. In this study, a systematic investigation was carried out to identify the effects of charge current/voltage and discharge current on energy recovery and electrode regeneration. By changing the charge current in CC (constant current) mode and voltage in CV (constant voltage) mode, the energy recovery rate was found to decrease with the increase of both charge current and voltage. Besides, with the increase of discharge current, the energy recovery rate also presented an obvious decrease trend, and the energy recovery rate in CC mode was generally higher than that in CV mode. It was showed that up to 46.6% of the energy used during charge cycle could be recovered during discharge cycle via an external load, which was achieved by charging and discharge the electrodes in a constant current 0.1 A. Furthermore, the study of electrode regeneration demonstrated that both in CC and CV modes, higher regeneration rate would be obtained with the decrement of discharge current, in which the regeneration was around 86% in CC mode and 64% in CV mode at 0.1 A discharge current. The relationship between energy recovery and charge/discharge condition was discussed in detail in this work, which was expected to provide a theoretical basis for practical application.