Electrosorptive removal of salt ions from water by membrane capacitive deionization (MCDI): characterization, adsorption equilibrium, and kinetics

Abstract

Capacitive deionization (CDI) was demonstrated to be an affordable technology for reduction of salt concentrations in brackish water. In this study, a novel membrane capacitive deionization (MCDI) cell was assembled by incorporating ion exchange membranes into the CDI cell which was built with high-adsorption electrodes based on ordered mesoporous carbon. The synthesized mesoporous carbon electrode was fully characterized. The simultaneous analysis of the electrosorption capacity and adsorption/desorption kinetics was evaluated by using real power plant desulfurization wastewater. The ordered mesoporous carbon was favorable for salt ion electrosorption, and the best performance was obtained by using MCDI which improved the removal efficiency of total dissolved solids (TDSs) from 65 to 82%. The total hardness and alkalinity of the effluent after treatment could meet the requirement of water quality standard for industries. Langmuir isotherm and pseudo-first-order kinetic models were found to be in best agreement with experimental results of salt ion electrosorption. The selective transport of ions between the electrode surface and bulk solution due to the ion exchange membranes resulted in a better desalination performance of MCDI. The results presented in this paper could be used for developing new electrode materials of MCDI for desalination from water.