Treatment of cork boiling wastewater by thermal wet oxidation processes

Abstract

This work explores the feasibility of Fenton oxidation and Catalytic Wet Peroxide Oxidation (CWPO) at high temperature for the treatment of a complex cork-boiling wastewater (CBW) characterized by a high organic load (COD = 4906 mg/L) and substantial content of phenolics. Since CBW leaves the process at 100 °C, working at high temperature favors the integration of an on-site thermal water treatment, as explored in this work. Fenton oxidation of CBW at 100 °C employing 100 mg/L Fe2+ and the stoichiometric dose of H2O2 for complete mineralization (H2O2 = 9795 mg/L), yielded around 70% TOC removal after 180 min reaction. In CWPO, four different catalysts were tested, 0.5wt.%Fe/SiC, 4wt.%Fe/SiC, AC (activated carbon) and 4wt.%Fe/AC also at 100 °C. The Fe catalysts exhibited significant activity that makes possible the disposal of the treated water to the environment. Nonetheless, the occurrence of significant iron leaching jeopardizes their stability and the process implementation. On the contrary , AC showed a great stability as evidenced by the well maintained COD and TOC removal efficiencies of 78 and 58%,respectively, in a long term run (72 h) at 100 °C. Based on these results, CWPO at 100 °C using AC as catalyst can be considered a promising alternative for the integration of an on-site CBW treatment.