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

Porous graphitized carbon (PGC)-supported CoFe₂O₄ bimetallic catalysts (CoFe₂O₄/PGC) were prepared by a hydrothermal method using Fe(NO₃)₃·9H₂O and Co(NO₃)₂·6H₂O as precursors and were used to activate peroxymonosulfate (PMS) for the degradation of chlorobenzene (CB). Under the conditions of CoFe₂O₄/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 SO₄^•- and HO^• were the main reactive radicals in the CoFe₂O₄/PGC-PMS system. In addition, the steady-state concentrations of SO₄^•- 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 CoFe₂O₄/PGC catalysts showed better electron transfer capacity and better activation of PMS compared with CoFe₂O₄ 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.