黑暗条件下Cu_2O/Ag_x复合催化还原Cr(Ⅵ)的研究

Study on the Reduction of Cr(Ⅵ) by Cu_2O/Ag_x Composite Catalyst in the Dark

采用一步液相还原法合成了系列Cu_2O/Ag_x复合催化剂,使用X射线衍射谱(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱(DRS)、电子顺磁共振谱(EPR)等分析手段对样品进行表征和分析.结果显示,复合催化剂Cu_2O/Ag_x表面附着大量的纳米金属Ag,形成无数的纳米岛,使得样品的表面等离子体共振效应大幅增强,导致催化剂在紫外、可见和近红外光谱区域的光吸收非常强.在无超声分散、黑暗条件下Cu_2O/Ag_x催化剂可以有效地还原Cr(Ⅵ),其中Cu_2O/Ag_(0.15)样品的催化还原效率最高.当存在0.01 mol/L的柠檬酸缓冲液(pH 5.0)时,100 mg/L的Cr(Ⅵ)在黑暗下于30 min内被完全还原为Cr(Ⅲ).另外,对Cu_2O/Ag_x体系催化还原Cr(Ⅵ)的机理以及柠檬酸的作用进行了初步探讨.

A series of Cu_2O/Ag_x composite catalysts were synthesized by a liquid phase reduction method. Synthesized Cu_2O/Ag_x samples were characterized by XRD,SEM,TEM,DRS and EPR methods. The results indicated that the surface of Cu_2O/Ag_x catalyst was coated by metallic Ag nanoparticles presenting like islands,which resulted in strong enhancement in plasmon resonance effect and the absorption of UV,Vis and NIR regions. Cr(Ⅵ) was reduced by Cu_2O/Ag_x composite catalyst in the dark without ultrasonic dispersion,thereinto,Cu_2O/Ag_(0.15) sample showed the strongest reducing capacity in all catalysts. In the presence of 0.01 mol/L citric acid buffer( pH 5.0),100 mg/L Cr(Ⅵ) was completely reduced to Cr( Ⅲ) in 30 min in the dark. The catalytic reduction mechanism of Cr(Ⅵ) by Cu_2O/Ag_x composite catalyst and the function of citric acid were proposed.