In this work, the elimination of hexabromocyclododecane (HBCD) is explored by using photodegradation of the UV/TiO₂ system, the UV/potassium persulfate (KPS) system, and the homo/heterogeneous UV/TiO₂/KPS system. The experimental results show that the dosages of TiO₂ and potassium persulfate have optimum values to increase the degradation degree. HBCD can be almost completely degraded and 74.3% of the total bromine content is achieved in the UV/TiO₂/KPS homo/heterogeneous photocatalysis, much more than in the UV/persulfate system and the UV/TiO₂ system. Roles of radicals SO₄^•− and OH^• in the photocatalysis systems are discussed based on experimental measurements. The high yield of the concentration of bromide ions and decreased pH value indicates that synergistic effects exist in the UV/TiO₂/KPS homo/heterogeneous photocatalysis, which can mineralize HBCD into inorganic small molecules like carboxylic acids, CO₂ and H₂O, thus much less intermediates are formed. The possible pathways of degradation of HBCD in the UV/TiO₂/KPS system were also analyzed by GC/MS. This work will have practical application potential in the fields of pollution control and environmental management.

Photodegradation of gas phase benzene by SnO₂ nanoparticles has been studied in humid air, dry air and N₂ by using a tubular photoreactor. The SnO₂ nanoparticles are synthesized by the oxidation of anhydrous stannic chloride (SnCl₄) in a propane/air turbulent flame. Direct hole oxidation and the ·OH radical mechanisms have been discussed based on experimental results. The goal of this research is to explore a viable and efficient alternative photocatalyst and photocatalytic process, in particular, for humidity-tolerant photocatalyst or photocatalytic process in environmental applications.

This paper has established a two-dimensional (2D) mathematical model for the generation, growth, and deposition of cigarette total particulate matter (TPM) in the smoldering state. The model has covered the chemical reactions and mass transfer as well as the mechanism of generation, flow, and condensation of particulate matter inside a burning cigarette. Cigarette smoke was generated by puffing under a constant pressure, and the pressure of the filter outlet was −274 Pa. The peak of the concentration of particulate matter was spatially overlapped with the peaks of pyrolysis and oxidation. Pertaining to the cross section of the cigarette at the same axial position, the peak of the diameter of particulate matter along the radial distribution first appeared in the zone near the edge of the cigarette cross section, and then gradually moved to the center of the cigarette with the cigarette smoke moving away from the combustion cone. The maximum number density of particulate matter calculated by the 2D mathematical model at the same axial position of the cigarette and the corresponding particle diameter, as well as the filtration efficiency of the filter rod, are in good accordance with the experimental data reported in previous studies.