Catalytic Effect of a Semiconductor on the Removal of Hexavalent Chromium from Aqueous Solution by γ-Ray Irradiation

Hexavalent chromium is a type of toxic chemical, it may cause allergies, hereditary genetic defects and cancer in humans by inhalation, and it is also a persistent danger to the environment. However, chromium metal, trivalent chromium and tetravalent chromium have low toxicities. In this study, semiconductor materials (quartz fibre and TiO2) were added to a hexavalent chromium solution and the removal efficiency of hexavalent chromium as a function of the gamma-ray irradiation dose, as well as the catalytic mechanism, was investigated. It was observed that the reduction of hexavalent chromium by gamma-ray irradiation was largely promoted in the presence of semiconductor materials; the semiconductor materials act as catalysts under the gamma-ray irradiation. The hexavalent chromium in the solution can be converted to an insoluble precipitate by gamma-ray irradiation. These results are highly beneficial to apply semiconductor materials as catalysts for the removal of contaminants by radiation.