Design and evaluation of a compact photocatalytic reactor for water treatment

Cubic structured SrTiO3 with Ce/Cr Co-doping for photoinduced catalytic oxidation of gaseous mercury

A cubic SrTiO₃ (STO) composite material co-doped with Ce and Cr ions was synthesized by solvothermal method. The fully characterized samples were employed as photocatalysts for the oxidation of Hg⁰. The co-doped samples afforded excellent catalytic removal efficiency of 98.99% using UV irradiation and 89.9% using visible light irradiation for Hg⁰ compared with the single-doped samples. It was found that co-doped samples had a lower electron-hole recombination rate, largest Brunauer-Emmett-Teller specific surface area, and reduced band gap. The electron spin resonance results revealed that ·O₂^- and ·OH were the main active species in the catalytic process. Moreover, the co-doped samples exhibited the best electron transfer rate and the highest photocurrent response intensity. The electron transfer between the elements in the co-doped sample enables it to achieve stable and efficient catalytic performance. In addition, even after five consecutive catalytic runs, the co-doped sample maintained high catalytic activity. This work highlights the potential of the perovskite-type STO materials in the photocatalytic oxidation of gaseous mercury.

Photocatalytic ozonation of organic pollutants in wastewater using a flowing through reactor

Photocatalytic ozonation (PCO/O₃) process is a promising technology for mineralizing refractory organics in wastewater. In this study, we described an efficient approach to improve the mass-transfer performance of PCO/O₃ by using a helical photocatalytic module (HPM) in an annular UVC reactor. Under hydraulic retention time (HRT) of 19 min and influent phenol concentration of 33 mg/L (TOC 26 mg/L), TOC removal of 91.5% was obtained during a PCO/O₃ process with HPM, while TOC removal was only 58.1% without HPM (UVC/O₃). This flowing through reactor displayed good stability in a continuous test lasting 20 h. The electric energy required to reduce TOC by one order of magnitude per cubic meter of solution was calculated to be 10.23 kWh/(m³ order), which supported that the PCO/O₃ process in this flowing through reactor was energy-efficient compared with other processes (24.30-68.75 kWh/(m³ order)). The steel-rolling wastewater after biological treatment was taken as a target. Under the HRT of 57 min and initial COD of 124 mg/L, COD in effluent dropped to 45.8 mg/L and met the discharge standard of pollutants for municipal wastewater treatment plant of China.

Analysis of a Hybrid Suspended-Supported Photocatalytic Reactor for the Treatment of Wastewater Containing Benzothiazole and Aniline

In this work, a study of the main operating variables affecting TiO2/UV photocatalysis was carried out. The treatment of an industrial effluent containing aniline and benzothiazole from the manufacture of accelerants for vulcanization was performed in a TiO2-supported commercial photoreactor. The degradation of both contaminants was monitored by GC-MS analysis. The proposed experiments were able to properly identify the phenomenon of adsorption, as well as to improve the performance of the commercial photoreactor by adding small amounts of TiO2 in suspension. The removal performance, durability of the photocatalytic material, and energy costs were analysed. The results showed that the use of suspensions intensifies the degradation obtaining an improvement of 23.15% with respect to the use of the supported catalyst. For an aniline and benzothiazole solution, the best operating conditions were found at pH = 12.0, introducing 60.0 mg L−1 of suspended TiO2 together with the existing supported catalyst.