A Novel Multi-Charged Draw Solute That Removes Organic Arsenicals from Water in a Hybrid Membrane Process.

The potential of forward osmosis for water treatment can only be maximized with suitable draw solutes. Here a three-dimensional, multicharge draw solute of decasodium phytate (Na-phytate) is designed and synthesized for removing organic arsenicals from water using a hybrid forward osmosis (FO) - membrane distillation (MD) process. Efficient water recovery is achieved using Na-phytate as a draw solute with a water flux of 20.0 LMH and negligible reverse solute diffusion when 1000 ppm organic arsenicals as the feed and operated under ambient conditions with FO mode. At 50 °C, the novel draw solute increases water flux by more than 30% with water fluxes higher than 26.0 LMH on the FO side, drastically enhancing water recovery efficiency. By combining the FO and MD processes into a single hybrid process, a 100% recovery of Na-phytate draw solute was achieved. Crucially, organic arsenicals or Na-phytate draw solutes are both rejected 100% and not detected in the permeate of the hybrid process. The complete rejection of both organic arsenicals and draw solutes using hybrid membrane processes is unprecedented; creating a new application for membrane separations.