Wet scrubbing coupled with advanced oxidation process for removal of chlorobenzene: A study of performance and mechanisms

Abstract

Porous graphitized carbon (PGC)-supported CoFe<inf>2</inf>O<inf>4</inf> bimetallic catalysts (CoFe<inf>2</inf>O<inf>4</inf>/PGC) were prepared by a hydrothermal method using Fe(NO<inf>3</inf>)<inf>3</inf>·9H<inf>2</inf>O and Co(NO<inf>3</inf>)<inf>2</inf>·6H<inf>2</inf>O as precursors and were used to activate peroxymonosulfate (PMS) for the degradation of chlorobenzene (CB). Under the conditions of CoFe<inf>2</inf>O<inf>4</inf>/PGC catalysts and PMS concentrations of 0.1 g/L and 5 mM, respectively, in a wide range of pH (5.0–9.0) both efficient removal (>68%) of 25 ppmv CB could be achieved. Electron spin resonance (ESR) and quenching experiments show that SO<inf>4</inf>^•− and HO^• were the main reactive radicals in the CoFe<inf>2</inf>O<inf>4</inf>/PGC-PMS system. In addition, the steady-state concentrations of SO<inf>4</inf>^•− and HO^• were estimated using the use of hydroxybenzoic acid (HBA) and benzoic acid (BA) as probes for 97.8 μM and 327.5 μM. Electrochemical characterization method demonstrated that the CoFe<inf>2</inf>O<inf>4</inf>/PGC catalysts showed better electron transfer capacity and better activation of PMS compared with CoFe<inf>2</inf>O<inf>4</inf> and PGC. The XRD and metal ion dissolution experiments (less than 0.33 ppm) illustrated that the catalysts possessed better stability before and after reaction. Moreover, the CB removal efficiency at 500 min remained at 77.6% after five runs. And the wet scrubber can remove gaseous CB, dichloroethane, trichloroethylene, dichloromethane over 70%. This study might provide a new idea for PGC-supported heterogeneous catalysts for CVOCs wet oxidation.