Catalytic ozonation of thymol in reverse osmosis concentrate with core/shell Fe_3O_4@SiO_2@Yb_2O_3 catalyst:Parameter optimization and degradation pathway

In this work, a novel catalyst of Fe_3O_4@SiO_2@Yb_2O_3 was prepared and the degradation of thymol in reverse osmosis concentrate using ozonation was explored. The operational parameters, such as ozone dosage(8–48 mg·min^(-1)),initial thymol concentration(20–100 mg·L^(-1)), initial pH value(3–11), and catalyst Fe_3O_4@SiO_2@Yb_2O_3dosage(0.2–1.0 g), were studied focusing on the thymol degradation and COD removal. The results indicated that the increase in ozone dosage, initial p H value, and Fe_3O_4@SiO_2@Yb_2O_3dosage accelerated the thymol degradation and COD removal, while the increase in initial thymol concentration hampered the effect of ozonation. A pathway of thymol degradation by catalytic ozonation was proposed based on the intermediates detected by gas chromatography-mass spectrometer and ion chromatography. This paper can provide basic data and technical alternative for pollutant removal from reverse osmosis concentrate by ozonation.

The Catalytic Effect of Metal Ions on the Degradation of 4-Chlorophenol Induced by an Aqueous Pulsed Discharge Plasma

The influence of metal ions, such as Fe^2＋, Fe^3＋, Cu^2＋ and Mn^2＋, on 4-CP degrada-tion was investigated in an aqueous pulsed discharge plasma system with or without the addition of a TiO2 photo-catalyst. From an analysis of the pseudo first-order rate constant （kcp） and energy efficiency （G50%） for 4-CP degradation, the experimental results show that the degrada- tion of 4-CP is much enhanced in the presence of ferrous ions at the optimal concentration of 0.2-0.8 mmol/L or 0.2 mmol/L in an aqueous pulsed discharge plasma without or with the TiO2 system, respectively, and the enhancement is ascribed to plasma induced Fenton and photo-Fenton reactions. Meanwhile, the rank of such metal ions for catalytic effect on 4-CP degradation was Fe^2＋〉 Fe^3＋ 〉 Cu^2＋ 〉 Mn^2＋ and Fe^2＋ 〉 Fe^3＋ 〉 Mn^2＋ 〉 Cu^2＋ for the former and the latter systems, respectively, and the reasons behind this were discussed through the analysis of active species, especially hydrogen peroxide.

Recent advances in metal organic frameworks for the catalytic degradation of organic pollutants

Metal organic frameworks(MOFs)with their large surface area and numerous active sites have attracted significant research attention.Recently,the application of MOFs for the catalytic degradation of organic pollutants has provided effective solutions to address diverse environmental problems.In this review,the latest progress in MOF-based removal and degradation of organic pollutants is summarized according to the different roles of MOFs in the removal reaction systems,such as physical adsorbents,enzyme-immobilization carriers,nanozymes,catalysts for photocatalysis,photo-Fenton and sulfate radical based advanced oxidation processes(SR-AOPs).Finally,the opportunities and challenges of developing advanced MOFs for the removal of organic pollutants are discussed and anticipated.

Efficient degradation of chlorobenzene in a non-thermal plasma catalytic reactor supported on CeO_2/HZSM-5 catalysts

Chlorobenzene removal was investigated in a non-thermal plasma reactor using CeO2/HZSM-5catalysts.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.