Anti-Wetting Membrane Distillation to Treat High Salinity Wastewater: Review

Abstract

Shortage of freshwater supply is now a pressing worldwide stress. While there is plenty of water on this blue planet, a major portion of it is inapt for human use due to its high salt content. A string of desalination technologies was thus presented to convert high salinity water sources into fresh ones. The conventional desalination technologies are capable to perform desalination effectively. Nonetheless, concern like their energy efficiency is put forward. Following that, this review aims to discuss the feasibility of employing membrane distillation (MD), an advanced application that outperforms conventional desalination technologies in terms of its energy efficiency to treat various kinds of high salinity wastewaters. Challenges associated with MD were investigated whereby emphasis was given to membrane pore wetting issue. The latter part of this review focused on resolving MD's challenges via synthesis of superhydrophobic membranes by inducing surface roughness and lowering surface energy of neat membranes. Various fabrication materials and modification methods such as direct manufacturing and addition of extrinsic additives to produce anti-wetting membrane were scrutinized. The superhydrophobic modification techniques include incorporation of nanoparticles, solvent exchange and plasma treatment, have successfully brought up the static contact angle of modified membranes to 150-173º. Those techniques resulted in enhanced permeate flow, with rejection of undesired component close to 100%. In short, MD demonstrates superiorities with regards to its thermal efficiency and stable desalting performances. MD also sees potentials in treating saline effluent from aquaculture, an imperative industry developed aggressively recently to bridge global food supply and demand.