Crude oil removal from water: Influence of organic phase composition and mineral content

Abstract

The removal of emulsified crude oil from industrial waters and the effects of organic and inorganic components commonly present in the mineralogy of crude oils on the de-oiling process were investigated.The goal of this work is to evaluate how the presence of organic and inorganic compounds commonly present in the mineralogy of crude oil and/or added in the washing processes of extracted oil affect the removal efficiency of emulsified oils present in waste washing waters by means of the use of flocculants.Approximately, 90% of the emulsified crude oil could be removed from water using an anionic flocculant, providing a residual turbidity below 100 NTU. However, the yield depended on the nature of the organic and inorganic components present in the emulsified crude oil.The higher the chain length of the main organic component, the greater the flocculant concentration required to remove the oil. Several components had an effect of emulsification (e.g. octane, decane), some of which rendered de-oiling process completely ineffective (e.g napthenic acids). Aliphatics were the most difficult to eliminate, requiring flocculant levels in the 200-300 ppm range. This is in contrast to 75-100 ppm were required to remove bi- and poly-cyclic aromatics. Heavy oils were more difficult to remove from water than light oils.There was a strong effect of the pH of the aqueous phase. The optimum was pH = 2.0. Virtually all inorganic compounds, which were selected as common components occurring in the mineralogy of extracted crude oils, reduced the efficiency of removing oil from water when spiked at 1%. The only exception was sodium carbonate which acted as a de-emulsifier. Monovalent salts has a minor effect on de-oiling, with efficiencies remaining at 80%. Divalent chlorides reduced the de-oiling efficiency to 70% while sulphates had a more severe influence. The de-oiling efficiency was lowered substantially with the addition of zinc, cadmium, ferric oxide, calcium carbonate and dibenyhlthiophene. Clays also reduced the efficiency of the de-oiling process. While bentonite had little effect, aluminum silicate, kaolin and magnesium silicate decreased the amount of crude recovered from industrial waters.