Assessment of polymeric flocculants in oily water systems

Abstract

Oil-in-water emulsions are usually formed during oil production and treatment. Before being discarded, such dispersions should be treated. In order to improve the oil–water separation process using physical processes (decantation, flotation, centrifugation, etc.) the particle size of the disperse phase should be increased. This may be achieved through flocculation, which consists in the agglomeration of various particles or drops, using, as flocculating agents, high molecular weight hydrophilic macromolecules. A few studies have been carried out on the flocculation of finely divided oil drops in brine with the aid of generally ionic polyelectrolytes. This work shows the results obtained using nonionic polymers as flocculants. Commercial samples of poly(ethylene oxide-b-propylene oxide) and poly(vinyl alcohol) were evaluated through flocculation–flotation tests as well as the drop size distribution. The performance of such additives as flocculants for oil–water dispersions is related to their structure, composition, molecular weight and hydrophilic–lipophilic balance. The composition of the produced water is also an important parameter when choosing the features of the flocculant additive.