Degradation of Biologically Treated Coking Wastewater over ${\mathrm{CuO}}_{\mathrm{x}}/\mathrm{PAC}$, ${\mathrm{CuO}}_{\mathrm{x}}/\mathrm{GAC}$, and ${\mathrm{CuO}}_{\mathrm{x}}/\mathrm{ACF}$ Catalysts under Microwave Irradiation in the Presence of ${\mathrm{H}}_2{\mathrm{O}}_2$

In this work, we adopted the impregnating-baking method to prepare ${\mathrm{CuO}}_{\mathrm{x}}$/granular activated carbon (GAC), ${\mathrm{CuO}}_{\mathrm{x}}$/activated carbon fiber (ACF), and ${\mathrm{CuO}}_{\mathrm{x}}$/powdery activated carbon (PAC) catalysts whose physicochemical properties were then investigated. The catalytic activities of the synthesized catalysts for degrading biologically treated coking wastewater (BTCW) were studied during the microwave-catalytic wet peroxide oxidation (MW-CWPO) process. The results showed that the catalytic activities were in the order of ${\mathrm{CuO}}_{\mathrm{x}}/{\mathrm{PAC}>\mathrm{CuO}}_{\mathrm{x}}/{\mathrm{ACF}>\mathrm{CuO}}_{\mathrm{x}}/\mathrm{GAC}$. When the catalyst and hydrogen peroxide (${\mathrm{H}}_2{\mathrm{O}}_2$) dosage is ($2\mathrm{g}/\mathrm{L}$, $0.9\mathrm{mL}/\mathrm{L}$), ($3\mathrm{g}/\mathrm{L}$, $4\mathrm{mL}/\mathrm{L}$), and ($15\mathrm{g}/\mathrm{L}$, $10\mathrm{mL}/\mathrm{L}$), the degradation efficiency is approximately 86.4%, 80.9%, and 78.8% for ${\mathrm{CuO}}_{\mathrm{x}}/\mathrm{PAC}$, ${\mathrm{CuO}}_{\mathrm{x}}/\mathrm{ACF}$, and ${\mathrm{CuO}}_{\mathrm{x}}/\mathrm{GAC}$, respectively. The enhanced catalytic activity of ${\mathrm{CuO}}_{\mathrm{x}}/\mathrm{PAC}$ can be attributed to greater adsorption and “hot spot” generation as well as sufficient contact among the catalyst, ${\mathrm{H}}_2{\mathrm{O}}_2$, and organics in aqueous solution resulting from its large specific surface area and small particle size. The hydroxyl radical (•OH) is proved to be the main active free radical based on free radical scavenging. The catalysts showed limited stability due to the leaching of Cu and catalyst crumble down, which poses an important challenge.