Recycling of oily ultrafiltration permeates to reformulate O/W emulsions

The feasibility of using ultrafiltration permeates to reformulate oil-in-water (O/W) emulsions was evaluated. In order to optimize the ultrafiltration process the effect of the operating conditions (crossflow velocity, transmembrane pressure and temperature) on permeate flux and chemical oxygen demand (COD) using two tubular ceramic membranes of 20 nm and 100 nm of pore size was studied. Moreover, the critical flux was determined for all operating conditions and for both membranes. Pumping energy consumption was calculated and optimum operating conditions for both membranes were chosen taking into account the minimum energy consumption at a transmembrane pressure well-below the critical pressure in order to minimize membrane fouling. The O/W emulsion was reformulated using the ultrafiltration permeate obtained at these optimum conditions and its properties (surface tension, contact angle, zeta potential, droplet size distribution, stability and foamability) were compared with those of the fresh emulsion. It may be concluded that the ultrafiltration permeate can be used to reformulate the O/W emulsion, taking into account its surfactant content.