title: Electrolysis-assisted mitigation of reverse solute flux in a three-chamber forward osmosis system.
abstract: Forward osmosis (FO) has been widely studied for desalination or water recovery from wastewater, and one of its key challenges for practical applications is reverse solute flux (RSF). RSF can cause loss of draw solutes, salinity build-up and undesired contamination at the feed side. In this study, in-situ electrolysis was employed to mitigate RSF in a three-chamber FO system ("e-FO") with Na2SO4as a draw solute and deionized (DI) water as a feed. Operation parameters including applied voltage, membrane orientation and initial draw concentrations were systematically investigated to optimize the e-FO performance and reduce RSF. Applying a voltage of 1.5 V achieved a RSF of 6.78 ± 0.55 mmol m-2h-1and a specific RSF of 0.138 ± 0.011 g L-1in the FO mode and with 1 M Na2SO4as the draw, rendering ∼57% reduction of solute leakage compared to the control without the applied voltage. The reduced RSF should be attributed to constrained ion migration induced by the coactions of electric dragging force (≥1.5 V) and high solute rejection of the FO membrane. Reducing the intensity of the solution recirculation from 60 to 10 mL min-1significantly reduced specific energy consumption of the e-FO system from 0.693 ± 0.127 to 0.022 ± 0.004 kWh m-3extracted water or from 1.103 ± 0.059 to 0.044 ± 0.002 kWh kg-1reduced reversed solute. These results have demonstrated that the electrolysis-assisted RSF mitigation could be an energy-efficient method for controlling RSF towards sustainable FO applications.
authors.affiliation: Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
authors.forename: Shiqiang
authors.initials: S
authors.lastname: Zou
authors.affiliation: Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA. Electronic address: zhenhe@vt.edu.
authors.forename: Zhen
authors.initials: Z
authors.lastname: He
mesh_terms: D004572:Electrolysis; D008567:Membranes, Artificial; D009995:Osmosis; D012996:Solutions; D062065:Wastewater; D018508:Water Purification
chemical_list: D008567:Membranes, Artificial; D012996:Solutions; D062065:Wastewater
keywords: Electrolysis; Energy consumption; Forward osmosis; In-situ mitigation; Reverse solute flux