Effect of reducing agent on catalytic hydrodechlorination of aqueous-phase OCDD/F

Removal/destruction of aqueous-phase octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) via hydrodechlorination process (HDC) is experimentally evaluated over palladium/activated carbon (Pd/AC) catalyst. Pd catalyst is mainly used as active component for effectiveness in removing dioxin from wastewater. Studies on the removal of PCDD/Fs accomplished with HDC reaction in aqueous phase are limited and the influencing factors have not been clarified. In this study, high-concentration OCDD/F are selected as targets, and the effects of solvent and operating temperature on dechlorination efficiency are investigated via experimental tests. The results indicate that the highest hydrodechlorination efficiency is achieved with isopropanol as solvent. The OCDD/F removal efficiency achieved with the solution of 80% isopropanol is higher than that of 50% isopropanol, whereas the destruction efficiency of OCDD/F reveals the opposite trend. Generally, the removal and destruction efficiencies of PCDFs are higher than those of PCDDs. In addition, the activation energies of OCDD and OCDF are calculated with the Arrhenius equation as 24.8 and 23.1 kJ/mol, respectively. Stability tests are conducted with three cycles. Overall, the results indicate that a high performance (≥99%) can be achieved by combining hydrodechlorination with Pd/AC at a temperature range of 303-353 K, demonstrating that Pd/AC has good potential for removing PCDD/Fs from wastewater.