Fabrication of MoS2-rGO and MoS2-ZIF-8 membranes supported on flat alumina substrate for effective oil removal

Abstract

In this research, reduced graphene oxide (rGO) and zeolitic imidazole framework-8 (ZIF-8) were used to functionalise molybdenum disulphide (MoS2). They were deposited as a thin-film composite membrane onto alumina support for oily water separation. The functionalisation of MoS2 aimed to control fouling activities on the membrane surface and enhance the permeation flux and oil rejection rate. Besides the physicochemical characterisation of MoS2–rGO and MoS2–ZIF-8 powder using FTIR and XRD, the surface morphology of the coated membrane was also investigated using contact angle analysis, mercury intrusion porosimeter, AFM, and FESEM. The impacts of operating parameters such as transmembrane pressure (TMP, 1–2 bar) and oil concentration in the feed water (Coil, 100–1000 ppm) were investigated in terms of permeate flux and oil removal efficiency using a dead-end permeation setup. The MoS2–rGO and MoS2–ZIF-8 deposition significantly increased the properties of the membranes and hold promise for oil/water separation due to the excellent permeation flux and oil rejection rate. A high permeation flux of 102.3 L·m-2·h-1 and 92.5% oil rejection were obtained at 2 bar and 100 ppm of feed concentration using MoS2–rGO/alumina membrane. This might be due to its hydrophilic properties and nanoporous multilayer 2D MoS2–rGO structure, which helped increase the permeate transport rate across the membrane and sieved the oil from entering the permeate stream. This work indicates that the coated alumina nanofiltration membrane has a high potential for oily wastewater treatment only if the operating conditions are optimised.