Cutting oil removal by continuous froth flotation with packing media under low interfacial tension conditions

Abstract

In this work, the froth flotation unit operated in a continuous mode was applied for oily wastewater treatment with the use of cutting oil as a model contaminant oil and sodium dodecyl sulfate (SDS) as a frother. The concentrations of the cutting oil and SDS were fixed constant at 500ppm and 0.1wt.%, respectively. The effects of salinity, air flow rate, hydraulic retention time (HRT), and the packing volume percentage of packing media on the process performance were studied. The results revealed that froth flotation efficiency was optimized under low interfacial tension (IFT) conditions which also simultaneously provided high froth formation and stability. The presence of packing media in the froth flotation column significantly improved cutting oil removal effectiveness. However, beyond the optimum packing volume of 50%, oil removal efficiency decreased markedly with increasing packing volume. The optimum operating conditions were found at a NaCl concentration of 6.0wt.%, an air flow rate of 200cm3/min, a HRT of 60min, and a packing volume of 50%, corresponding to a cutting oil removal of 98.1%, an enrichment ratio of cutting oil of 2.3, a surfactant removal of 84.9%, and an enrichment ratio of surfactant of 7.8.