Potential use of nanofiltration like-forward osmosis membranes for copper ion removal

Abstract

The discharge of industrial effluent containing heavy metal ions would cause water pollution if such effluent is not properly treated. In this work, the performance of emerging nanofiltration (NF) like-forward osmosis (FO) membrane was evaluated for its efficiency to remove copper ion from water. Conventionally, copper ion is removed from aqueous solution via adsorption and/or ion-exchange method. The engineered osmosis method as proposed in this work considered four commercial NF membranes (i.e., NF90, DK, NDX and PFO) where their separation performances were accessed using synthetic water sample containing 100 mg·L−1 copper ion under FO and pressure retarded osmosis (PRO) orientation. The findings indicated that all membranes could achieve almost complete removal of copper regardless of membrane orientation without applying external driving force. The high removal rates were in good agreement with the outcomes of the membranes tested under pressure-driven mode at 1MPa. The use of appropriate salts as draw solutes enabled the NF membranes to be employed in engineered osmosis process, achieving a relatively low reverse solute flux. The findings showed that the best performing membrane is PFO membrane in which it achieved > 99.4% copper rejection with very minimum reverse solute flux of < 1 g·m−2·h−1.