**4.2. Ultrafiltration (UF)**

Ultrafiltration membrane process can separate compounds between 0.005 ≈ 10 μm which is between MF and RO [36]. UF membranes are highly prominent water filters with low energy consumption in removal of pathogenic microorganisms, macromolecules and suspended maters among others [37]. However, UF has some limitations including its inability to remove any dissolved inorganic substances from water and regular cleaning to maintain high pressure water flow [38]. Mocanu and others developed a synthetic procedure for hybrid ultrafiltration membrane for water treatment. They used wet-phase inversion method with polysulfone and graphene nanoplatelets modified with poly (styrene) to obtain their membranes. ZnO was deposited on one surface of the membrane with polymers that are soluble in water [39]. In the study reported by Igbinigun and others, the modified GO-membrane showed 2.6 times better flux recovery compared to the unmodified membrane and this shows that it is wise to modify membrane with GO to increase flux recovery. They used a simple method known as UV induced amination which has high flux UF membrane found to be resistant to organic fouling, and the resulting membrane can be applied in waste water treatment application. Incorporating hydrophilic materials onto the surface of these polymers will lead to more hydrophilic surface membrane [40].
