TREATMENT OF OIL EMULSIONS

Abstract

Oil-Water emulsions are formed due to dispersion of small stable droplets (dp<3.tm) and/or the mixture of soluble oils in water. Soluble oils in aqueous solutions are used extensively in the engineering metal-working industries, as coolants and/or lubricants. Hysol-X oil is a general purpose cutting oil used in 2-10% concentration in aqueous solution. Central pollution Control Board (CPCB), Delhi has prescribed effluent standards, for several parameters, including that for oil/grease, which is 10 mg/I for effluent discharge into sewers. In view of the CPCB standards, it is necessary that the oil-water emulsion is treated to remove/recover oil so conform to the oil concentration of 10 mg/I in the supernatant aqueous phase for discharge into sewers. Deemulsification or oil splitting for the removal/recovery of oil is carried out by concentrated acid and different coagulants. In the present work, concentrated hydrochloric acid and coagulants/flocculants such as alum, ferric chloride, ferrous sulfate, polyaluminium chloride(PAC SAB-18,obtained from M/S Grasim Industries Ltd., Nagda) and surefloc (obtained from, M/S DSCL chemicals Ltd., Kota) were used to treat ofw emulsion containing 2.5%,5%,7.5% and 10% oil. All the chemicals used, were found to produce pH dependent performance. The optimum flocculation pH, have been found to be 6.0 for alum and surefloc, 7.0 for PAC SAB-18,and 10.0 for FeCI3 and FeSO4.Single stage treatment has been found to be inadequate. However, a two stage treatment has been found to produce aqueous supernatant meeting the prescribed limit of 10 mg/1 of oil.