Novel chemical modification of polyvinyl chloride membrane by free radical graft copolymerization for direct contact membrane distillation (DCMD) application

Polyvinyl chloride-graft-poly ethyl acrylate (DHPVC-g-PEA) novel membranes were prepared for highly saline water desalination using DCMD. Free radical graft copolymerization was used to prepare DHPVC-g-PEA by applying an ethyl acrylate (EA) onto a PVC polymer backbone. The influence of the grafting reaction time on the PVC grafting percentage and on the resulting copolymer's characteristics was measured. The DHPVC-g-PEA preparation was affirmed via Fourier-transform infrared (FTIR) and energy-dispersive X-ray (EDX). The use of EDX revealed a new peak associated with oxygen, while the increased carbon percentage confirmed that an ester group was present on the PVC backbone. The best reaction time for obtaining excellent DHPVC-g-PEA membrane properties for membrane distillation (MD) application was 1 h. The following membrane characteristics were investigated: atomic force microscopy (AFM), contact angle (CA), scanning electron microscopy (SEM), thickness and porosity as well as the pore size and how it was distributed. Grafting PVC by the 1-hr reaction time of the EA affected the morphology of the modified membranes and decreased the membrane thickness, whereas the mean and maximum pore size as well as the roughness and contact angle were improved. The DHPVC-g-PEA membrane's upper surface had a very porous structure. The pure water permeate flux of the DHPVC-g-PEA membrane was enhanced by approximately twelvefold. When operated under the specified conditions (i.e., 35, 70, 100, and 200 g/L; 0.6 L/min; and 65 °C), the DCMD results for the DHPVC-g-PEA membrane demonstrated that its salt rejection was greater than 99.9%, with a permeate conductivity below 27 μS/cm.