Oil pollution in water and separation of oil from water are receiving much attention in recent years due to the growing environmental concerns. Membrane technology is one of the emerging solutions for oil-water separation. However, there is a limitation in using polymeric membrane for oil water separation due to its surface properties (wetting behaviour), thermal and mechanical properties. Here, we have shown a simple method to increase the hydrophilicity of the polyethersulfone (PES) hollow fibre ultrafiltration (UF) membrane by using carboxyl, hydroxyl and amine modified graphene attached poly acrylonitrile-co-maleimide (G-PANCMI). The prepared membranes were characterized for its morphology, water and oil contact angle, liquid entry pressure of oil (LEPoil), water permeability and finally subjected to a continuous 8 h filtration test of oil emulsion in water. The experimental data indicates that the G-PANCMI play an important role in enhancing the hydrophilicity, permeability and selectivity of the PES membrane. The water contact angle (CAw) of the PES membrane is reduced from 63.7 ± 3.8° to 22.6 ± 2.5° which is 64.5% reduction while, the oil contact angle was increased from 43.6 ± 3.5° to 112.5 ± 3.2° which is 158% higher compared to that of the PES membrane. Similarly, the LEPoil increased 350% from 50 ± 10 kPa of the control PES membrane to 175 ± 25 kPa of PES-G-PANCMI membrane. More importantly, the water permeability increased by 43% with >99% selectivity. Based on our findings we believe that the development of PES-G-PANCMI membrane will open up a solution for successful oil-water separation.

Bio-fouling is a serious problem in many membrane-based separation processes for water and wastewater treatment. Current state of the art methods to overcome this are to modify the membranes with either hydrophilic additives or with an antibacterial compound. In this study, we propose and practise a novel concept to prevent bio-fouling by developing a killing and self-cleaning membrane surface incorporating antibacterial silver nanoparticles and highly hydrophilic negatively charged carboxylic and amine functional groups. The innovative surface chemistry helps to reduce the contact angle of the novel membrane by at least a 48% and increase the pure water flux by 39.4% compared to the control membrane. The flux drop for the novel membrane is also lower (16.3% of the initial flux) than the control membrane (55.3% of the initial flux) during the long term experiments with protein solution. Moreover, the novel membrane continues to exhibit inhibition to microbes even after 1320[emsp14]min of protein filtration. Synthesis of self-cleaning ultrafiltration membrane with long lasting properties opens up a viable solution for bio-fouling in ultrafiltration application for wastewater purification.

In this study, polyelectrolyte assembled functionalized graphene oxide (PE-GO) membranes were fabricated through a one-step charge facilitated deposition method for high performance dye/salt separation. According to the intercalation of polydopamine (PDA) and (ionic liquid) IL functional moieties into the GO membranes, the pore size of the resulted PE-pGO and PE-iGO membrane increased from 2.69 nm to 4.13 nm and 6.54 nm, respectively. Correspondingly, a pure water flux of 13.8 ± 2.2, 36.7 ± 3.4, and 52.1 ± 6.7 L m⁻¹ h⁻¹ bar⁻¹ was achieved for PE-GO, PE-pGO and PE-iGO membrane, respectively. PE-iGO membrane with the largest pore size could be operated with significant water permeability (28.3 to 38.3 L m⁻¹ h⁻¹ bar⁻¹) at a low operating pressure range of 0.5–2 bar (dye concentration = 100 ppm, salt concentration = 5 g/L). More importantly, functionalities introduced to the GO nanosheets are found to impact the dye adsorption to the membrane surface. The IL intercalation promotes the elution of dye molecules from the IL moieties at elevated pH, therefore enhancing the efficiency of alkaline washing of the membrane. By contrast, the intercalation of PDA weakens such efficiency due to its strong adhesion force to the dye molecules even at the alkaline condition.