Insights into Probing\nthe Effect of Molecular Weight\nof Poly(carboxybetaine methacrylate) on the Performance of Forward\nOsmosis Desalination

Zwitterionic polymers have proven to be a promising nonfouling\nmaterial that can be applied in the design of selective layers of\nthin film composite (TFC) membranes. Extending the permeability and\nusage of TFC membranes have attracted increasing interest in membrane-based\ndesalination processes since water-flux reduction associated with\nbiofouling nowadays persists as a common challenge. By virtue of its\nstrong hydration, this polymer category is very useful to counteract\nbiofouling in marine and biomedical systems, but the benefits from\ntheir application in membrane technology are still emerging. The efficacy\nof the nonfouling property as a function of the polymer’s molecular\nweight remains unknown. In pursuit of that vision, this study fosters\nnew scientific insights via probing different molecular weights of\npoly(carboxybetain methacrylate) (PCBMA) coated on the surface as\na selective layer for the prepared TFC membranes. The coated zwitterionic\nmembranes (zM) exhibited excellent performance in preventing water\nflux decay in a bench-scale forward osmosis system. The prepared zM\nmembranes revealed enhanced hydrophilic properties and retained their\noperational water flux when compared to the control. Our results suggest\nthat using an intermediate-size molecular weight (PCBMA <i>M</i><sub>n</sub> 50,000) will result in the best operational performance.\nThe intermediate size resulted in the lowest flux decline rate (<i>R</i><sub>t</sub>) of 0.01 ± 0.001 (zM-50) when compared\nto the unmodified control membrane 0.56 ± 0.071 (M0) after using\na model BSA foulant solution. Furthermore, all coated membranes exhibited\nsimilar trends in the observed reverse salt flux profiles, as well.\nThe constructed zM membranes will serve as a model to develop further\nselective layers in the construction of TFC membranes.