Nanofiltration and hybrid membranes for water reuse

Interest in industrial water reuse has risen due to increasing water demands and future regulations on the concentration of pollutants in wastewater discharge. Nanofiltration (NF) membranes have already been widely used in various industrial applications such as reducing hardness of process water, removal of organic molecules from oil-gas process water and protein separation in the dairy industry. However high concentrations of dissolved solids, the presence of organic foulants, precipitating solids, and trace contaminants pose challenges for conventional membranes. This work seeks to utilize both NF membranes and hybrid membranes containing graphene oxide quantum dots and iron nanoparticles for the purpose of industrial water reuse. High TDS (~10,000 ppm) scrubber wastewater from Plant Bowen Georgia was treated by combined NF and hybrid membrane treatment. Over 80% of the water was recovered for reuse, while maintaining an overall rejection greater that 60% of Ca2+, Cl-, Mg+, and SO42- the major ions in the water. Selenium concentration was reduced from 1 mg/L to less than 10 μg/L through after treatment. Graphene oxide (GO) has been shown to have antifouling properties due to its hydrophilicity, and consequently there have been multiple investigations into GO modified membranes. Graphene quantum dots (GQDs), two-dimensional nanoparticles between 2-5 nm, have greater functionality than GO due to increased edge area, high water solubility, and photo-reactive properties. These GQDs were further integrated into existing NF and UF membrane to create hybrid membranes with antifouling properties. GQD functionalized membranes exhibit enhanced negative charge as determined by zeta potential measurement. The hindrance of BSA fouling and CaSO4 scaling caused by GQD functionalization will be further analyzed in batch and cross flow experiments