Chlorobenzene removal was investigated in a non-thermal plasma reactor using CeO2/HZSM-5 catalysts. The performance of catalysts was evaluated in terms of removal and energy efficiency. The decomposition products of chlorobenzene were analyzed. The results show that CeO2/HZSM-5 exhibited a good catalytic activity, which resulted in enhancements of chlorobenzene removal, energy efficiency, and the formation of lower amounts of by-products. With regards to CO2 selectivity, the presence of catalysts favors the oxidation of by-products, leading to a higher CO2 selectivity. With respect to ozone, which is considered as an unavoidable by-product in air plasma reactors, a noticeable decrease in its concentration was observed in the presence of catalysts. Furthermore, the stability of the catalyst was investigated by analyzing the evolution of conversion in time. The experiment results indicated that CeO2/HZSM-5 catalysts have excellent stability: chlorobenzene conversion only decreased from 78% to 60% after 75 hr, which means that the CeO2/HZSM-5 suffered a slight deactivation. Some organic compounds and chlorinated intermediates were adsorbed or deposited on the catalysts surface as shown by the results of Fourier Transform Infrared (FT-IR) spectroscopy, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses of the catalyst before and after the reaction, revealing the cause of catalyst deactivation.Download high-res image (83KB)Download full-size image

•Fe–Mn binary oxide was synthesized using simultaneous oxidation and coprecipitation.•It has high removal efficiency toward Co(II).•The thermodynamic parameters of Co(II) sorption on Fe–Mn binary oxide was calculated.•The mechanism of Co(II) on the surfaces of Fe–Mn binary oxide was studied.•Mn was reduced when Co(II) was oxidized to Co(III), while Fe showed no difference.An amorphous Fe–Mn binary oxide adsorbent was developed using simultaneous oxidation and coprecipitation, and characterized by Brunauer–Emmett–Teller analysis, X-ray diffractometry, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The removal behavior of the prepared absorbent for cobalt (II) was studied. Results showed that iron and manganese in adsorbent existed mainly in the +III and +IV oxidation states, respectively. The adsorbent exhibited the best depletion of Co(II) at pH 6–8, and the best removal ability at an ionic strength of 0.01 mmol L−1. The Freundlich isotherm model fitted the Co(II) adsorption data best. The FTIR spectra of the absorbent before and after Co(II) adsorption showed that the surface hydroxyl groups, Mn–OH and Fe–OH, existed at the surface and formed Mn–O–Co or Fe–O–Co. The iron oxide was the main adsorbent, and the manganese oxide also showed adsorption and oxidation ability. The XPS spectra confirmed that the Mn in the absorbent was reduced whereas the Fe showed no difference after reaction with Co(II). The XPS measurements of cobalt adsorbed on the adsorbent indicate that Co(II) has been oxidized to Co(III).