Treatment of oil-in-water emulsions by a destabilization/ultrafiltration hybrid process: Statistical analysis of operating parameters

Abstract

A hybrid process has been studied for an oil-in-water (O/W) emulsion treatment. This process consisted of two stages: emulsion destabilization by coagulation/centrifugation with calcium chloride, and subsequent ultrafiltration (UF) using a 300 kDa tubular multichannel ZrO2 ceramic membrane. The O/W emulsion was formulated from a commercial oil concentrate (1 wt % in distilled water) used in metalworking processes. The hybrid process was optimized in terms of ultrafiltration permeate flux and permeate quality parameters, such as chemical oxygen demand (COD), pH, conductivity and turbidity. Experiments’ planning was designed using Taguchi method to determine the influence of four parameters (transmembrane pressure, feed flow rate to the UF module, destabilization temperature, and coagulant salt molar concentration) on a response factor, with three levels for each of them. The contribution of each factor was determined using a statistical analysis of variance (ANOVA). Transmembrane pressure and temperature were the most significant factors affecting permeate flux, while permeate quality, expressed as COD, was mainly influenced by UF feed flow rate and temperature. This behavior was slightly different when ultrafiltration was performed with 300 kDa flat ZrO2 ceramic membranes.