Heterogeneous activation of peroxymonosulfate over porous graphitized carbon-supported CoS catalyst for efficient removal of gaseous chlorobenzene

Chlorobenzene (CB) is a typical example of chlorinated volatile organic compounds (CVOCs) that require pollution control. Using wet scrubbers coupled with advanced oxidation processes (AOPs) has become a promising technique to degrade gaseous CVOCs. Here, a CoS-loaded porous graphitized carbon (PGC) served as an adsorbent for CVOCs and a catalyst to activate peroxymonosulfate (PMS) to construct a wet scrubber for CB degradation. CoS/PGC exhibited excellent catalytic performance at pH 9.0; a 0.1 g/L CoS/PGC dosage and a 10 mM initial PMS concentration achieved 90% CB (25 ppmv) removal within 500 min. Electron spin resonance and quenching experiments identified hydroxyl radicals and sulfate radicals as the main reactive oxygen species that removed CB. In addition, we proposed possible CB degradation pathways by intermediates identified using liquid chromatography-mass spectrometry and density functional theory calculations. Electrochemical experimental results such as cyclic voltammetry and Nyquist proved that CoS/PGC has superior electron transport capacity compared to CoS. A possible catalytic mechanism for CB removal in CoS/PGC + PMS system was proposed by ESR and XPS spectra. By using continuous dosing or pulsed dosing to replenish PMS to maintain its suitable concentration, the system achieves a commendable long-term efficiency. Moreover, this catalyst displayed excellent recyclability and universal applicability to treat various gaseous CVOCs as well as the scrubbing solution replacement with tap water for efficient CB removal. This study may provide new fundamental insights into the PGC-supported catalysts for wet oxidation of CVOCs or other contaminants.