Performance and Mechanism of Chlorine Dioxide on BTEX Removal in Liquid and Indoor Air

With the development of the chemical industry, benzene, toluene, ethylbenzene, and xylene (BTEX) have gradually become the major indoor air pollutants. Various gas treatment techniques are widely used to prevent the physical and mental health hazards of BTEX in semi-enclosed spaces. Chlorine dioxide (ClO₂) is an alternative to chlorine as a secondary disinfectant with a strong oxidation ability, a wide range of action, and no carcinogenic effects. In addition, ClO₂ has a unique permeability which allows it to eliminate volatile contaminants from the source. However, little attention has been paid to the removal of BTEX by ClO₂, due to the difficulty of removing BTEX in semi-enclosed areas and the lack of testing methods for the reaction intermediates. Therefore, this study explored the performance of ClO₂ advanced oxidation technology on both liquid and gaseous benzene, toluene, o-xylene, and m-xylene. The results showed that ClO₂ was efficient in the removal of BTEX. The byproducts were detected by gas chromatography-mass spectrometry (GC-MS) and the reaction mechanism was speculated using the ab initio molecular orbital calculations method. The results demonstrated that ClO₂ could remove the BTEX from the water and the air without causing secondary pollution.

Self-Promoted H2 Formation: The Feasibility of Photoinduced CO Removal for Lossless Hydrogen Purification

A photoinduced radical reaction operated at low temperature can be used to remove trace CO from a H₂ stream by minimizing the reverse water-gas shift. However, H₂ consumption resulting from nonselective oxidation by hydroxyl radicals becomes an obstacle to practical hydrogen purification. Inspired by hydrogen exchange transfer, we demonstrate here that molecular hydrogen can promote H₂ formation from hydrogen radicals, which are generated from the reaction of CO and H₂ with hydroxyl radicals. The slight increment in H₂ along with the radical reaction encouraged us to configure a photocatalytic hydrogen purification fixed-bed reactor, which can reduce CO to ≤1 ppm in the H₂ stream.

Revealing the role of surface elementary doping in photocatalysis

Doping CdS with manganese can catalyze hole extraction and facilitate interfacial electron transfer to metallic cocatalyst. This reduces the activation energy for spatial separation of photogenerated charge carriers and enhances photon utilization.