Incorporating graphene nanosheets in PDMS membrane: Effects of filler functionalization on pervaporation performance

Graphenic materials including Graphene oxide (GO) functionalized with butylamine/octadecylamine (GOButA, GOODA) and their chemically-reduced derivatives (rGO, rGOButA, rGOODA) were used in polydimethylsiloxane/polyethersulfone membranes to increase the enrichment factor for pervaporative removal of toluene from water. The characteristics of synthesized nanosheets assessed by FTIR, XPS, XRD, RAMAN, SEM, and TGA showed that the graphenic materials were properly synthesized, functionalized, and reduced. The membrane-filler interactions were assessed by the contact angle, solvent uptake, and pervaporation. The pervaporation showed incorporating GO or GOButA resulted in deterioration of enrichment factors down to 51% and 34% (comparing to the neat PDMS membrane) due to increase the membrane's hydrophilicity and affinity to water by oxygen functional groups while GOODA increased the enrichment factor by 12%. Using chemically-reduced derivatives of rGO, rGOButA, and rGOODA, the enrichment factors were increased by 110, 130, and 449%, respectively. Increasing the alkyl chain length of functionalizing groups on the nanosheets causes their higher hydrophobicity and better dispersion, which result in decrease of free energy and water flux and ultimately enhancement in the membrane's enrichment factor. The improvement in performance by incorporating the nanosheets was verified by comparing the results of present research with those in literature based on a developed boundary.