Application of a newly-designed capacitive deionizing membrane distillation (CDIMD) technique for the efficient production of high-quality drinking water from seawater

Abstract

A newly-designed capacitive deionizing membrane distillation (CDIMD) system which introduced the activated carbon fiber felt (ACFF) electrodes and self-fabricated electrically conductive membranes (CNTs-PTFE) into the convention MD technique for the efficient production of high-quality drinking water from seawater in this work. Two different CDIMD systems of forward-CDIMD (ACFF linking to positive poles) and reversed-CDIMD (ACFF liking to negative poles) were established in this study to investigate the impacts of electric field form on the desalination efficiency. The severe membrane flux decline of MD (83.17%, 168 h) was clearly mitigated in the CDIMD system, which was respectively 52.93% and 69.82% for the forward-CDIMD and reversed-CDIMD group. In terms of the CDIMD system without input voltage, an anabatic flux drop to 8.85% was observed in the later period, implying the necessity of periodic regeneration for ACFF and CNTs-PTFE. The membrane scaling induced by the deposition of CaSO4, as the core drawback of MD application, has been remarkably solved in the CDIMD system, especially in the forward-CDIMD system. Although the ACFF and CNTs-PTFE were periodically regenerated in the forward- and reversed-CDIMD system, an increasing appearance of crystals was observed inside the ACFF and CNTs layer along with the long-term seawater desalination, accordingly degrading their electrochemical performance. Hence, the forward-CDIMD system with an abbreviated time-set of adsorption/desorption phase might be a superior choice for efficient seawater desalination.