Underwater Superoleophobic Graphene Oxide-based Membranes For Emulsified Oil Wastewater Treatment

The discharge of oily wastewater and oil spills have caused serious damage to the ecological environment and human health.Compared with traditional water treatment methods,membrane separation technology is widely used in the treatment of oily wastewater because of its advantages such as simple operation,high efficiency,low energy consumption,high speed and no secondary pollution.Moreover,the emulsion is difficult to be processed by conventional methods because of its small particle size and stable properties.Therefore,the development of high flux,high efficiency,simple process and anti-fouling membranes has become a research hotspot in the treatment of oily wastewater,especially emulsified oil wastewater.In this paper,three novel composite membranes were prepared by graphene oxide as the matrix with functionalized nanomaterials.The main contents are as follows:?1?Copper hydroxide nanowire-graphene oxide?CHNs-GO?hydrophilic-superoleophobic composite membrane was prepared and oil-water separation performance was tested.By vacuum-assisted filtration self-assembly process,graphene oxide nano-sheets were used as substrates,copper hydroxide nanowires were embedded,and the nanochannels of the composite materials were expanded to prepare a composite membrane with hydrophilicity and underwater superoleophobicity.The results showed that the water and oil contact angles of the composite membrane reached 53°and 155°,respectively,and the membrane flux was 349 L·m^-2h^-1bar^-1.The oil removal rate was as high as 99%,and the cycle performance was good.The membrane had anti-fouling performance,after 10 cycles of recycling,the oil-water separation efficiency remained at 98%.?2?Dopamine-modified copper hydroxide nanowires-ethylenediamine-graphene oxide?D-CHNs-EDA-GO?hydrophilic-superoleophobic membrane was prepared and oil-water separation performance was tested.Dopamine-modified copper hydroxide nanowires and ethylenediamine was introduced to increase the hydrophilic groups and further increase the hydrophilicity.The prepared composite membrane was hydrophilic in air and superoleophobic in water.The water contact angle and oil contact angle were29°and 161°,respectively.The membrane flux was 369 L·m^-2h^-1bar^-1.In addition to good oil-water separation performance,the filter also has good removal effeciency of dye.After 10 cycles,the oil removal efficiency was about 99%,and the dye removal rate was higher than 97%.?3?Dopamin-nano-zinc oxide-reduced graphene oxide?PDA-ZnO-RGO?superhydrophilic-superoleophobic free-standing membrane was prepared and oil-water separation performance was tested.Dopamine was used to modify and reduce graphene oxide,nano-zinc oxide improved the surface properties and morphology and adjusted the channel structure between nano-sheets to prepared the superhydrophilic-underwater superoleophobic multi-functional membrane.The results showed that the water and the oil contact angles of the composite membrane were 2°and 160°,respectively.The oil-water separation efficiency of various emulsion such as soybean oil,diesel oil,and toluene exceeded 99%,and the flux was 72 L·m^-2h^-1bar^-1.At the same time,the membrane was resistant to membrane fouling and the flux recovery was as high as 94%.After 10 cycles,the removal rate remained above 99%.In addition,the free-standing membrane also has photocatalytic effect of the MB dye.After 150 min of visible light irradiation,the degradation efficiency reached over 98%.