Physicochemical Characterization and Kinetic Study of Flotation Process Applied to the Treatment of Produced Water

Produced water (PW) discharged into the Mediterranean basin is a mixture of organic and inorganic materials of high toxicity and risk to the marine environment. This PW had a high water mineralization and significant amounts of suspended matter (SM). The detected levels of heavy metals, especially Ag+, Ba2+ and Pb2+ cations, were not negligible. The values of chemical oxygen demand (COD 735 mg/L) and total organic carbon (TOC 93.83 mg/L), which were very high, confirmed the presence of large concentrations of polycyclic aromatic hydrocarbons (PAHs) which were identified by infrared analysis. The total concentration of polycyclic aromatic hydrocarbons (PAHtot) in the PW sample was about 3.243 g/L. This can be treated by flotation in a very acidic medium at pH=2, in the presence of a neutral collector (Tween 80) at 0.5%, with an optimum cleaning efficiency of 93.67%, without necessarily generating the production of polluted sludge, in about 20 min, optimum time of flotation found. A study of flotation kinetics based on PAHtot recovery was carried out. It showed that the process followed Higuchi model. At the end of the treatment, all effluents were corrected from the acidic pH to the neutral pH, before to be discharged into the sea.