Cr(Ⅵ) is one of the most widespread heavy-metal pollutants mainly from electroplating, metallurgy, textile, printing and dyeing, leather, ceramics, pharmaceuticals and other industries, existing widely in water and soil. The popular treatment methods of Cr(Ⅵ) in wastewater are physical, chemical, biological methods and so on. Photocatalytic reduction, as an advanced chemical method, is an ideal method for treating Cr(Ⅵ) in wastewater. This paper is focused on the research progress of photocatalytic reduction of Cr(Ⅵ) in wastewater both at home and abroad. According to the type of the photocatalysts, the advantages and disadvantages of the photocatalysts are analyzed, and the possible photocatalytic mechanisms are presented. The synergistic effect by adding photo-induced hole scavenger, mainly organic matters, is important and effective for improving the photocatalytic efficiency of Cr(Ⅵ) and economic and practical in real wastewater application. The trends of photocatalytic reduction methods are also pointed out. The developing directions of the photocatalysis are seeking catalysts with higher catalytic activity, expanding the light responding range of photocatalysts and effectively designing combined system including Cr(Ⅵ) and other pollutants which can be removed by photocatalysis simultaneously. Besides, composite catalysts made of two or more materials, and photocatalytic reduction coupled with other methods are also the trends for treating Cr(Ⅵ) in the future.

Contents
1 Introduction
2 Photocatalytic reduction of Cr(Ⅵ) by TiO₂
2.1 Pure TiO₂ photocatalysis
2.2 Modified TiO₂ photocatalysis
3 Photocatalytic reduction of Cr(Ⅵ) by other photocatalysts
4 Photocatalytic reduction of Cr(Ⅵ) by composite photocatalysts
5 Synergistic effect
6 Combination of photocatalytic technology and other methods
7 Conclusion and outlook