Fabrication of polycarbonate ultrafiltration mixed matrix membranes including modified halloysite nanotubes and graphene oxide nanosheets for olive oil/water emulsion separation

In this study, ultrafiltration polycarbonate mixed matrix membranes (MMMs) were synthesized to remove the olive oil from the aqueous solution. To characterize the synthesized membranes in terms of surface morphology, functional groups, hydrophilicity, and mechanical strength, various analyses such as FESEM, FTIR, contact angle, and tensile strength were carried out, respectively. Modified halloysite nanotubes and graphene oxide nanosheets with the loading of 0.25, 0.5, and 0.75 wt% were added to the blank membrane. Membranes including modified halloysite nanotubes exhibited better hydrophilicity and higher pure water flux due to the presence of amphiphilic sodium dodecyl sulfate surfactant at higher nanoparticle loadings, while the agglomeration of graphene oxide nanosheets in the membrane polymeric matrix resulted in the lower pure water flux compared to the blank PC membrane. Moreover, the pure water flux data were modeled by Design-Expert software, and the highest pure water flux of 1340 L/m(2) h was reported for PC-MHNT0.75 MMM. Then, the optimized membranes based on the output of the design expert software were used in the ultrafiltration tests for olive oil removal. All the selected membranes reached 100% rejection efficiency of olive oil; however, they were different based on the time to reach this efficiency and the permeate flux. Performance evaluation of membranes in ultrafiltration tests at different feed concentrations showed that the PC-MHNT0.75 mixed matrix membrane possessed the lowest time (165 min at 100 ppm feed concentration) to reach 100% rejection efficiency and subsequently selected as the optimal membrane. The regeneration process using 20% (v/v) acetone solution was implemented for the optimal membrane and the obtained membrane water flux after three cycles of regeneration was more than 96%, introducing the fabricated MMMs as suitable candidates for olive oil separation.