Electro-peroxone treatment of Orange II dye wastewater

Degradation of a synthetic azo dye, Orange II, by electro-peroxone (E-peroxone) treatment was investigated. During the E-peroxone process, ozone generator effluent (O2 and O3 gas mixture) was continuously sparged into an electrolysis reactor, which was equipped with a carbon-polytetrafluorethylene (carbon-PTFE) cathode to electrochemically convert the sparged O2 to H2O2. The in-situ generated H2O2 then reacted with the sparged O3 to produce •OH, which can oxidize ozone-refractory organic pollutants effectively. Thus, by simply combining conventional ozonation and electrolysis processes, and using a cathode that can effectively convert O2 to H2O2, the E-peroxone process degraded Orange II much more effectively than the two processes individually. Complete decolorization and 95.7% total organic carbon (TOC) mineralization were obtained after 4 and 45 min of the E-peroxone treatment, respectively. In comparison, only 55.6 and 15.3% TOC were mineralized after 90 min of the individual ozonation and electrolysis treatments, respectively. In addition to its high efficiency, the E-peroxone process was effective over a wide range of pH (3-10) and did not produce any secondary pollutants. The E-peroxone process can thus provide an effective and environmentally-friendly alternative for wastewater treatment.