Preparation Of Cu₂O And CuS Nanocrystals And Their Performance For Reduction Of Cr（Ⅵ） Ions

Hexavalent chromium Cr(VI), which has great harm to humans and the environment with high stability in natural environment, is intensive carcinogenicity and teratogenicity accoding to previous reports. Trivalent chromium Cr(III) is slightly toxic and can be easily precipitated or adsorbed on top of a solid phase. Therefore, development of effective technologies to reduce Cr(VI) to Cr(III) is of great importance in the treatment of wastewater. Photocatalysis has been considered to be a quite attractive, efficient and clean strategy to reduce the toxic Cr(VI) species to less harmful Cr(III) species. Cu2 O and Cu S, which could response under visible light, are important p-type semiconductors with narrow bandgap suitable for sunlight utilization.The present work stars with the preparation of of Cu2 O and Cu S with different morphologies, then characterizing Cu2 O and Cu S nanocrystals with XRD, SEM, BET and FT-IR, and evaluating their performance for photoreduction of Cr(VI) ions under visible light irradiation. The main points are as follows:1. Cubic Cu2 O microcrystals was synthesized via a hydrothermal method and used for the photoreduction of Cr(VI) ions under UV radiation. Operating parameters such as dissolved oxygen levels, the hole scavenger, and the p H of solution were examined in detail to determine the optimal experimental conditions. Results showed that the kinetic process is a pseudo-first-order reaction. The presence of dissolved oxygen has no effects to the process. The photocatalytic of Cr(VI) was obviously promoted by methanol, the more methanol, the faster Cr(VI) ions photoreduction rate. Reduction is more efficient at p H=5 under the tested conditions.2. Cu2 O octahedrons, rhombic dodecahedrons and cubes, were prepared and evaluated in the reduction of hexavalent chromium under visible light irradiation. Results reveal that the specific activity of Cu2 O with different crystal planes follows {111} > {110} > {100}, and the surface capping ligands of octahedral and rhombic dodecahedral Cu2 O have no blocking effect on their photocatalytic performance.3. Cu S nanoplates, spheres, flower and tubes were prepared and evaluated in the reduction of hexavalent chromium under visible light irradiation. Results reveal that Cu S architectures with high surface area exhibit high and stable photocatalytic performance for reduction of Cr(VI) and the activity order of Cu S with different morphologies follows plate > tube > flower > sphere.