High-Flux Sodium Alginate Sulfate Draw Solution for Water Recovery from Saline Waters and Wastewaters via Forward Osmosis

Abstract Forward osmosis (FO) is one of the new membrane processes used to recover water from wastewater. FO as a low-energy treatment method requires a draw solution instead of a hydraulic force. Therefore, introducing an optimal draw solution for more prolific commercial FO technology applications is a chronic issue. In this report, sodium alginate sulfate (SAS) was simply synthesized, characterized, and employed as a biodegradable osmotic agent in the FO process. The sulfonation degree, ion exchange capacity, and concentration of SAS as a draw solution were optimized. The polyionic structure of the SAS increased its hydrophilicity and osmotic pressure. The average water flux for 0.11 g mL–1 SAS solution was obtained as 28.5 L m–2h–1 with the reverse solute flux of 3.4 g m–2h–1 using deionized water as feed solution. The SAS was successfully used as a draw solution for brackish and brine water and the Caspian Seawater in the FO process. The wastewaters from various sources, including domestic, oil and gas refinery, petrochemical, power plant, food, pharmaceutical, and automotive manufacturing, have been utilized as feed solutions for FO treatment. The results showed that the SAS was also useful for water recovery from wastewater. The low-pressure reverse osmosis process was accomplished to regenerate the SAS draw solution easily. The regenerated draw solution was repeatedly used for the FO process.