Investigation of heavy oil refinery wastewater treatment by integrated ozone and activated carbon -supported manganese oxides

• Biodegradability of treated refinery wastewater (HORW) was improved by MnOx/GAC + O3.
• The reaction was dominated by hydroxyl radical OH mechanism.
• The highest COD removal efficiency was obtained over catalyst MnOx/GAC-2.
• H/C and O/C of organic pollutants increased during the treatment by ESI-FT-ICR MS.
• The number of Ox compounds increased from 847 to 973 during the treatment.

The activated carbon-supported manganese oxides (MnOx/GAC) was utilized for catalytic ozonation of heavy oil refinery wastewater (HORW). MnOx/GAC was characterized by XRD, SEM & EDS, TGA and N2-adsorption–desorption. The effects of reaction parameters on HORW treatment were investigated. COD, BOD5, TOC, biodegradability, toxicity, simulative activated sludge processes and ESI-FT-ICR MS analysis were used to analyze HORW samples. MnOx/GAC exhibited greater COD reduction efficiency in the catalytic ozonation of HORW than did GAC. The dominant mechanism of HOPW catalytic ozonation was oxidation via hydroxyl radicals over MnOx/GAC. The results suggested that big molecular pollutants with high toxicity and low biodegradability were first degraded to small molecular oxidation products with low toxicity and high biodegradability, afterward which small molecular pollutants and oxidation products further oxidized or mineralized. The investigation uncovered the industrial potential of MnOx/GAC for ozonation treatment of refinery wastewater.