A novel membrane-promoted crystallization process integrating water recovery and salt production for brine management

Abstract

Brine management is one of the global challenges nowadays. Herein, by taking advantage of capillary forces and low-grade heat (50 °C), we propose a novel ceramic membrane-promoted crystallization (MPC) process for brine management. The MPC process simplifies the traditional multiple energy-intensive steps and dispenses the use of expensive anticorrosive equipment via adopting three hierarchical layers (α-Al2O3 substrate, γ-Al2O3 interlayer, and SiO2 top layer). The hydrophilic mesoporous SiO2 top layer provides continuous driving force for brine solution transport from the inner shell of the membrane toward the outer surface, where heterogenous nucleation and secondary nucleation occur to form numerous long needle-like salt whiskers. The growth kinetics of salt whiskers accelerates with time as the formed salt whiskers provide extra evaporation area to intensify water evaporation. Template-directing molecules P123 significantly enhance the specific surface area, pore volume, pore size, and pore regularity of the SiO2 top layer, thereby promoting both water recovery and salt production. The optimized membrane displays high water recovery (790.3 g m−2) and salt production (194.6 g m−2) for high-salinity brine (20 wt%). Moreover, the MPC process demonstrates high performance, mechanical stability and thermal durability during the long-term test. It is expected that the MPC process would provide an innovative zero-liquid discharge approach for the efficient and low-cost brine management.