Separation of oil-water emulsion by cellulose acetate ultrafiltration membranes

This study reports the separation of oil from water using cellulose acetate (CA) ultrafiltration (UF) membranes. The CA membranes were fabricated by varying bath temperatures such as 5 ± 2°C, 25 ± 2°C and 45 ± 2°C using the phase inversion technique and assess their performance based on the oil removal efficiency. Changing the coagulation bath temperature (CBT) at that stage of membrane formations affects the porosity, pore size, hydraulic resistance, morphological structure and performance of membranes. The obtained results revealed increased porosity and pore size and also decreased hydraulic resistance of the membranes as the CBT increases. Field Emission Scanning Electron Microscopy (FESEM) images indicate that a large number of surface pores are visibly found at the higher bath temperature. Atomic force Microscopy (AFM) images show increased average roughness (R_a) of the membrane as the CBT of the membrane increases. The water flux and permeate flux of all the membranes tend to increase with an increase in CBT. From Chemical Oxygen Demand (COD) studies, the oil removal efficiency was maximum for the lower bath temperature membrane. The results indicate that conditions of the coagulation bath significantly affect the porous structure, morphology and performance of the membrane.