Responsive switchable wettability membrane prepared via hydrogel coating and its performance recovery evaluation via membrane distillation

Excessive fouling and wetting phenomenon during long term membrane distillation (MD) cause membrane degradation and lead to consistent need for membrane replacement. Hence, effective cleaning of fouled membrane is imperative to recover its performance without compromising structural integrity. In this work, poly(N-isopropylacrylamide) (PNIPAM) hydrogel was coated on the hydrophobic PTFE support via spray coating (SC) method to fabricate membrane with switchable wettability for membrane cleaning. By using bovine serum albumin (BSA) and sodium alginate (SA) as model foulants, the antifouling property of hydrogel coated membrane (HCM) was evaluated. Furthermore, chemical-less thermal cleaning on the fouled HCM membrane using water at different temperature was tested to determine its water flux recovery. The interchanging hydrophilic/hydrophobic properties of PNIPAM around its LCST facilitated the foulants removal. It was found that the PNIPAM layer could fully coat the membrane and the flux of HCM performance can be recovered by up to 59.58% and 73.66% after subjecting to fouling by bovine serum albumin (BSA) and sodium alginate (SA). Surface free energy study also showed that hydrogel incorporation could ease the removal of BSA and SA upon water cleaning and does not contribute to wetting phenomenon.