稻壳炭基高比表面多孔氧化硅的表征及Cu(Ⅱ)吸附特性

Characterization and Cu(Ⅱ)adsorption property of rice-husk-char-based porous silica with large specific surface area

以热解稻壳炭为原料,H3PO4为酸化剂,聚乙二醇为模板剂,制得了多孔氧化硅;采用N2吸脱附、X射线荧光光谱、X射线能谱、X射线衍射等测试技术表征了制得的多孔氧化硅,采用批量吸附实验考察了它对水溶液中Cu(Ⅱ)的吸附特性。结果表明:以稻壳炭为原料,可以在10h内制得比表面积达957m2.g-1、二氧化硅含量为99.26%的无定形多孔氧化硅;该氧化硅含有中孔与微孔,中孔率为38.6%。在Cu(Ⅱ)初始浓度为20～120mg.L-1时,它对Cu(Ⅱ)的最大吸附量、最高脱除效率分别为77mg.g-1、97%;该多孔氧化硅对铜的吸附符合Freundlich等温线及准二级动力学模型。

Porous silica with a large specific surface area （SSA） was prepared from rice husk char （RHC） by adding H3PO4 to sodium silicate solution （SSS） until the solution reached pH 4.1. The preparation process consisted of formation of SSS from RHC, that of silica-polyethylene glycol （PEG） composite by using SSS, H3PO4 and PEG, and calcination of the composites. The porous silica as-prepared was characterized by N2 adsorption, X-ray fluorescence, X-ray energy dispersive spectrometer, X-ray diffraction, and Fourier transform infrared spectroscopy. Their characters for Cu（ Ⅱ ） adsorption were investigated by batch adsorption experiments. The results show that amorphous silica with specific surface area of 957 m^2 · g^- 1 and silica content of 99.26% can be obtained from rice husk char within 10 h. The porous silica contains both micropores and mesopores, with the mesopore fraction up to 38.6%. The advisable contact time and solution pH for Cu （Ⅱ） adsorption required are higher than 2 h and 6.0, respectively. The largest adsorption capacity and highest removal efficiency for Cu（ Ⅱ ） at initial Cu （ Ⅱ ） concentrations of 20-120 mg · L^-1 are 77 mg· g^-1 and 97%, respectively. The adsorption of Cu（ Ⅱ） onto the silica could be well described by the Freundlich isotherm and the pseudo-second-order model.