Application of the electrical localized heating method in direct contact Membrane Distillation Crystallization process

Abstract

Membrane Distillation Crystallization (MDCr) was the latest technology which shows great ability in the salt recovery area, but its practical application is currently confined to the laboratory due to the energy loss during long hydraulic circulation, and the high energy consumption caused by the long-term thermal requirements of the feed solution. In this study, the electric heating method was applied in the MDCr system as a potential candidate to increase the solution temperature and enhance the thermal efficiency. Compared to the normal water bath heating, the electrothermal MDCr system exhibited better permeate flux performance, higher thermal efficiency and high controllability. Additionally, the permeate flux decline under the control of AC 20 V was 11.1 %, which was far below the flux drop of 31.6 % obtained by the water bath method. Noticeably, the accumulation of NaCl crystals on the membrane was greatly alleviated according to the in-situ monitor of OCT due to the constant ion migration responding to the electric field within the conducting membrane. We hold the belief that this electrothermal direct contact MDCr system has a promising potential in the treatment of saline wastewater, building an effective foundation for efficient and energy-saving electrical heating MDCr systems.