Effect of pH on the performance and durability of NBR latex/graphene oxide-based membranes

Post-vulcanised latex curing method was adapted in this study to develop nitrile butadiene rubber/graphene oxide (NBR/GO) membranes for oily wastewater filtration. This is a comparatively new method for solvent-free membrane preparation. Due to the fact that the oily wastewater could be discharged at different pH in industry, the pH reading of the oily wastewater in this study was varied from 4 to 10 to investigate its effect on the membrane performance in terms of tensile strength, permeation flux, and oil rejection efficiency. Performance of latex-based membranes over a range of pH has yet to be reported in literature. Thus, the knowledge from this work has significant impact on future applications of latex-based membranes to treat wastewater discharged at different ranges of pH. NBR/GO membranes were found to have good retention of tensile properties at all pH ranges. This feature is attributed to the crosslinks in the NBR matrix which provides a strong and stable three-dimensional network between the polymeric macromolecules. Moreover, with incorporation of 2 wt% GO, the NBR/GO membrane was able to achieve permeation flux of more than 500 L/m 2 .hr and oil rejection of more than 50% at all pH ranges. This can be attributed to the membrane's average pore size of 0.2810 µm and a water contact angle of 75°, both of which concurrently manifest oil rejection and water flux characteristics. The highest permeation flux and oil rejection of 2720.53 L/m 2 .hr and 91.88%, respectively, were achieved at a pH range of 6–7.