Low carbon desalination using nanofiltration pretreatment and membrane contactor

Abstract

The current global water shortage issue is becoming increasingly severe, and research into desalination processes as a solution is actively in progress. Traditional thermal distillation and membrane-based desalination processes have the disadvantages of high costs and greenhouse gas emissions. As an alternative, this study proposes a new desalination process using nanofiltration membranes and membrane contactors. Using nanofiltration membranes with over 90% divalent ion removal efficiency, seawater was pretreated, reducing the cost of reverse osmosis processes. The increase in recovery during pretreatment improved salt rejection and also increased the ion concentration in the retentate. The concentrated divalent ions were used in a carbon dioxide mineralization reaction, utilizing a silane-treated hollow fiber membrane contactor, thereby removing carbon dioxide. The carbon dioxide removal rate and flux were compared by varying the liquid and gas flow rates, and the mass transfer coefficient of the membrane was calculated using the Wilson plot. This coefficient demonstrated higher values compared to existing membranes, proving the efficiency of the membrane. The operation of the membrane contactor for five days confirmed that the membrane pores were not easily wetted and there was minimal fouling.