Combination of photoelectrocatalysis and ozonation as a good strategy for organics oxidation and decreased toxicity in oil-produced water

Abstract

The oil-produced water generated during drilling of oil wells and gas extraction has been a cause for great concern since it contains a complex mixture of different organic and inorganic compounds, large amount of CO2, grease, salts, minerals, oils, and many hazardous compounds. The present work investigates the efficiency of photocatalysis (PC), photoelectrocatalysis (PEC), ozonation (O3), and photoelectrocatalysis coupled with ozonation (PEC+O3) in the removal of organic and inorganic contaminants in the oil-produced water monitored by Gas Chromatography-Mass Spectrometry (GC-MS) and Ionic Chromatography (IC) techniques. Parameters such as toxicity, which was investigated using Zebrafish embryos, color, turbidity, pH, quantity of dissolved solids, conductivity, chemical oxygen demand (COD), and concentrations of organic and inorganic carbon were also investigated. The best results were obtained by coupling PEC and O3 techniques, which presented superior reduction in color (98%), turbidity (100%), inorganic carbon (99%), COD (73%), and a decrease of 96% in the fluoride and 35% in the chloride detected previously in the real oil-produced water. Among the 12 organic compounds identified in the oil-produced water, the PEC+O3 treatment reached complete oxidation in eight of them and a lower Zebrafish embryo mortality occurred with 12.5% of dilution after 2 h treatment.