Ionic Liquids and Activated Carbon: Effective Materials for the Sustainable Production of Fresh Water from Salt Effluents (BRINE)

Abstract

Water stress in Morocco is a major concern and considerably affects the economic and social sectors. Seawater desalination processes are part of the solutions adopted, and direct contact membrane distillation (DCMD) processes have been proposed to treat salty discharge from reverse osmosis units. Recently, composite polymer membranes based on ionic liquids (ILs) have been adopted for extraction and separation processes. In this context, a composite membrane was prepared based on polymer supports poly(vinylidene fluoride) (PVDF) and polysulfone (PSU) and ionic liquid trioctylmethylammonium oleate (TOMAO) and doped with activated carbon (AC). The PVDF/PSU-IL-AC membrane has been adopted in DCMD processes for the diffusion and extraction of water vapor (WV). This composite membrane has good hydrophobicity (126.04°) and high porosity (91.07%). Significant flux 18.29 kg m–2 h–1 and salt rejection 99.93% were observed at 60 °C, with good reproducibility of the results (9 weeks). The activation parameters Ea, ΔH#, and ΔS# were quantified, the diffusion mechanism of water molecules through the membrane has been identified, and the roles of IL and AC have been elucidated. All results indicate that the developed membrane is an effective tool for producing pure water from saline waters (BRINE). Finally, seawater desalination tests were carried out under optimal conditions.