Application of Terminalia catappa wood-based activated carbon modified with CuO nanostructures coupled with H2O2 for the elimination of chemical oxygen demand in the gas refinery.

This study focused on the reduction of chemical oxygen demand (COD) from gas refinery wastewater via copper oxide nanoparticles which loaded on activated carbon supplied from Terminalia catappa (CuO-NPs-TCW-AC), while accordingly understudy process was accelerated by decomposition of organic pollutants in the presence of H2O2 as oxidant. CuO-NPs-TCW-AC as heterogeneous catalyst in the combination of H2O2 lead to generating OH radical as most efficient species degradation of organic pollutants (it is expected that copper ions also exhibited somewhat Fenton-like behaviors). TCW-AC prepared by carbonization at 850 °C for 90 min and subsequently was activated with CO2 at 900 °C for 90 min and TCW-AC as the final product was oxidizing with nitric acid and hydrochloric acid solution. Characterization of adsorbent and investigation of mechanism process were undertaken by FT-IR (before and after COD removal), pHZPC, Boehm's titration method, SEM, XRD, BET, and BJH. Conduction of preliminary experiments reveals that setting experimental condition at their optimum values including 0.06 g of the CuO-NPs-TCW-AC, pH of 4 and 0.1 mol L−1 of H2O2 at 75 °C following 5 min agitation at speed of 400 rpm leads to 61.5% reduction of initial COD (320 ppm) from gas refinery wastewaters. According to the coefficients of determination (R2) for Langmuir (0.985), Freundlich (0.993) and Temkin isotherm (0.981) reveal cooperative mechanism on whole adsorption/decomposition process, while its experimental and calculating maximum adsorbent capacity were 250.1, 263.2 (mg g−1), respectively. Judgment based on correlation coefficients represents an agreement among experimental and predicted adsorption capacity and confirms that understudy COD reduction using CuO-NPs-TCW-AC follows the second-order kinetics. The negative Gibbs free energy strongly support the high tendency of present material for COD through spontaneous while, higher adsorption rate by temperature rising confirm the endothermic nature of the process. As a result, the application of CuO-NPs-TCW-AC in the combination of H2O2 is suggested as a powerful tool for COD reduction from gas refinery wastewater. [ABSTRACT FROM AUTHOR]