Application of capacitive deionizing membrane distillation (CDIMD) system for seawater desalination: Emphasizing on the impacts of operating parameters

Abstract

Although membrane distillation (MD) is highly regarded as a promising technique for seawater desalination, membrane scaling induced by the accumulation of crystals is the crucial obstacle for real application of MD. Capacitive deionization (CDI), another novel desalination technology, is mainly applied in the desalination of hyposaline water, and its desalination efficiency is inferior to MD. Even so, the electro-absorption desalination mechanism of CDI is a novel enlightenment for alleviating MD scaling. Hence, we developed a new-type desalination technique by integrating CDI with traditional MD system to retard MD scaling, namely capacitive deionizing membrane distillation (CDIMD) technique. In the CDIMD system, the anions and cations were respectively separated by the activated carbon fiber felt (ACFF) electrodes and lab-made electrically conductive membranes (CNTs-PTFE), accordingly alleviating the combination of salt ions and the subsequent membrane scaling development. The influences of crucial operation parameters of CDIMD on the desalination efficiency were deeply researched. The results revealed that feed temperature of around 65 °C, feed flow velocity of 15.72 mm/s, operating mode of forward-CDIMD, input voltage of 1.2–1.6 v, CNTs thickness of 40–60 μm, and a short time-set of ion-adsorption/desorption phases (9/1 min and 17/3 min) might contribute to the CDIMD desalination.