Recently, there is a growing interest in membrane distillation (MD) technology, a thermally driven membrane separation, to treat high salinity water or contaminated wastewater. However, MD commercialization is still limited by technical challenges such as temperature polarization (TP), scaling, and high-energy consumption, as the feed solution requires continuous heating to provide an efficient driving force. We suggest and assess the ability and efficiency of ‘self-heating’ thermally conducting membranes heated by radio frequency induction heating (RF-IH), to overcome distillation limitations. A composite membrane containing iron oxide coated carbon nanotubes (Fe-CNTs) (Fig.1 A) was spray coated on a PTFE membrane and heated by induction heating, using radio frequency (RF) altering magnetic fields (Fig.1 B). The performance of RF-MD system was evaluated in terms of distillate flux and specific heating energy consumption at optimized operating conditions and results were compared to a conventional MD system. In addition, the impact of RF heating on calcium sulfate (CaSO4) scaling was addressed in terms of distillate flux and crystal formation. Results show the ability of heating water directly on the membrane surface in RF-MD systems, leading to low TP, high distillate flux, and low specific heating energy compared to a conventional MD system (Fig.1 C). Scaling results showed the impact of RF magnetic field on salts crystallization, leading to smaller crystal size and overall less scaling. Following analysis of the RF-MD membrane surfaces, only sporadic small CaSO4 crystals were detected, while high concentrations of small crystals were detected at the concentrate stream exiting the MD process. These results are promising as they show the RF-MD system has potential to improve MD processes, specifically for high salinity distillation where pressure-based applications cannot be used.

Performance enhancement and scaling mitigation of radio frequency induction heated membranes in vacuum membrane distillation

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.