Treatment of Produced Water Using Dissolved Air Flotation (DAF) Technique and Ionic Liquids

Abstract

As population grows, more water and oil resources are needed to make more products. In addition, more contaminants are also created due to daily uses. Consequently, environment protection will be a necessary duty for everyone. As produced water is a by-product from the oil production process, and constitutes a large portion of the extracted liquid from the oil well, treatment of the produced water is necessary before discharging. Treatment of produced water is a benefit for many reasons such as extracting more oil from the produced water, using the treated water for irrigation, and finally for protecting the environment. In the present research, dissolved air flotation technique (DAF) was used to study the optimum removal efficiency of oil, chemical oxygen demand, turbidity and total organic carbon using different coagulants. Five types of coagulants were used in the experiments. A widely used coagulant (aluminium sulphate), and four more environmentally friendly ionic liquids (1-methyl-3-octylyimidazolium tetrafluoroborate, 1-methyl-3-octylimidazolium hexafluorophosphate,1-butyl-3-methylimidazalium bis(trifluoromethyl- sulfonyl)imide and 1-dodecyl-3-methylimidazolium chloride) were assessed. 1-Butyl-3-methylimidazalium bis(trifluoromethyl sulfonyl)imide was not the appropriate ionic liquid to be used with the dissolved air flotation technique due to its anionic nature in the aqueous media, which helped make the emulsion stable by decreasing the zeta potential below -30 mV. The best removal efficiencies of oil were those of alum (93.83%) and 1-methyl-3-octylimidazolium hexafluorophosphate (93.26%). 1-Methyl-3-octylyimidazolium tetrafluoroborate, 1-dodecyl-3-methylimidazolium chloride could successfully removed 88.01% and 90.46% of the oil, respectively. According to the results, 1-dodecyl-3-methylimidazolium chloride was a strong cationic ionic liquid which could be used in the emulsion if higher amounts of oil content were present.