STUDIES ON THE DEEMtJLSIFICATION OF OILY WASTES BY POLYMERIZED ALUMINUM SALTS

Abstract

Suspended particles, colloidal in nature, are not easily removed. Normally chemical agents like coagulants are used to remove such particles and to reduce the turbidity of water. Conventional coagulants like alum, ferrous sulphate and ferric chloride have been used for a long period for effectively reducing suspended particulate turbidity. Oil emulsions also reduce the transparency and the photo-oxygenation capacity of water. Oil emulsions are normally removed by chemical methods, using conventional and non-conventional coagulants. Amongst non-conventional coagulants are poly-aluminum chloride (PAC) and poly-aluminum sulphate (PAS). Present work deals with the splitting of the emulsion formed of soluble cutting oil using alum, ferrous sulphate and ferric chloride as conventional coagulants and poly-aluminum chloride as the non-conventional coagulant. Varying combinations of coagulants and lime/sulphuric acid were used in the study. Various parameters like turbidity, coagulant dose, pH and sludge volume generated were studied. In a simple, one-step process, PAC, a pre-formed/hydrolyzed coagulant, was synthesized from aluminum sulphate and sodium bicarbonate. The alum-sodium bicarbonate solution was kept undisturbed at a constant temperature for about three months and then the solution was used. The quantification of the degree of polymerization was not possible. Coagulants containing pre-formed polymeric species of Al (III) appear to be more effective than alum when the colour and turbidity in the raw water are low. PAC gives better turbidity removal within certain coagulant dosages.