Vacuum Evaporation of Waste Oil-in-Water Emulsions from a Copper Metalworking Industry

The performance of vacuum evaporation was evaluated for the treatment of waste oil-in-water (O/W) emulsions, one synthetic (Multiroll) and two semisynthetic (Unopol and Divinol), used in a copper metalworking industry. A destabilization/settling pretreatment step using Nalco 71243 (NAL, a quaternary polyamine) as flocculant and CaCl2 and AlCl3·6H2O as coagulants was also investigated. The quality of the final aqueous effluent was evaluated in terms of chemical oxygen demand (COD), turbidity, conductivity, and biological oxygen demand (BOD5). COD reduction greater than 99% was achieved. The pretreatment step did not significantly improve either the evaporation rate or the quality of the condensate. Moreover, evaporation of a totally exhausted Unopol waste emulsion carried out in an industrial falling film evaporator showed good agreement with results obtained at the laboratory scale.