CUTTING FLUID OILY WASTEWATER: BREAKDOWN AND REUSE OF THE RECOVERED OIL PHASE

Abstract

The aim of this work is to evaluate the use of electrolytes in the breakdown of waste by cutting fluid emulsions, reusing the recovered oil phase to develop new cutting fluids. Four cutting fluids were used to obtain oily emulsions: two commercial, OP38 (Lubrax) and Dromus (Shell), and two developed formulations, CF1 and CF2. The emulsions were prepared by using 5 to 30 wt.% cutting fluid in water. NaCl and CaCl2 solutions were used to promote the destabilization of emulsions, taking into account the percentage of oil recovered as a function of time, observing the influence of type and concentration of electrolyte, temperature, and emulsion droplet size. The aqueous effluent obtained after oil phase removal was characterized by turbidity, oil and grease content, pH, and presence of anions and cations. The use of CaCl2 (2 wt.%), at 25°C, provided the best results in emulsion breakdown and the best quality of the water phase. All the parameters evaluated in these water phases were in accordance with the specifications established by Brazilian legislation that regulates the disposal of wastewater in surface waters. The physicochemical properties of the recovered oil phases were compared with the ones of the mineral oil NH-20 used to obtain CF1 and CF2. It was verified an increase in total acid number, viscosity and corrosiveness to copper. Additives were added to the recovered oil phases to obtain new cutting fluids. The physicochemical properties of these new cutting fluids were close to the ones of the initial ones, except for the viscosity values which increased.