Concentrating esterquat-based surfactant wastewater via forward osmosis: A step toward reuse

This study investigates the potential of forward osmosis (FO) for concentrating industrial wastewater obtained from the rinsing stage of esterquat-based cationic surfactant production. The raw wastewater exhibited a high chemical oxygen demand (COD) of approximately 20,000 mg O 2 /L and a significant concentration of cationic surfactants (CSs) from the esterquat group (∼2,500 mg/L). The FO process with 1 M NaCl reduced wastewater volume by 50%, resulting in a twofold increase in COD and CSs. An increase in the feed solution salinity (67 to 612 mg Cl - /L) confirmed the occurrence of reverse salt flux, while total organic carbon (TOC) in the draw solution at the end of the process reached ∼200 mg/L, indicating partial organic contaminants transfer through the membrane. These results demonstrate that FO is effective for concentrating wastewater and supports circular economy strategies by enabling water reuse and reducing freshwater consumption.