三水铝石(γ-Al(OH)_3)和α-Al_2O_3表面酸碱性质与磷酸根吸附研究

Studies on the surface acid-base properties and phosphate adsorption behavior of gibbsite (γ-Al(OH)_3) and α-Al_2O_3

采用批量实验法，对2种不同晶体结构铝氧化物（γ-Al（OH），和α-l2O3）表面上磷酸根的吸附进行了比较研究．吸附等温线实验在pH=4和pH=6的KNO3溶液（0．01mol·L^-1）中进行，并使用Langmuir等温方程进行定量描述．由吸附等温线可以发现，α-l2O3表现出更大的吸附容量和吸附密度．且在pH3．5—4．0范围内，表面对磷酸根的吸附达到最大值．为了更好的理解表面性质对磷酸根吸附的影响，使用X射线衍射、N2吸附比表面积分析、电镜观察和表面酸碱滴定技术对表面结构和性质进行了表征．结合表面信息和吸附结果可以发现，单位质量吸附剂上的吸附量大小与比表面积有关．而吸附密度与铝氧化合物表面对磷酸根的吸附反应活性有关．

The adsorption of phosphate on two crystallized aluminum oxides, gibbsite and α-l2O3 , was studied. The adsorption experiments were carried out in 0.01 mol· L ^- 1 KNO3 solutions at pH 4 and pH 6, respectively. Adsorption densities were calculated to evaluate the phosphate adsorption affinity to two aluminum oxides. To better understand the effect of surface properties on the adsorption behavior of phosphate, the surface structure and properties were investigated by X-ray diffraction, N2 adsorption-desorption, electron microscope observation and acid-base titration. The results from adsorption isotherms showed that at both pH 4 and pH 6, α-l2O3 exhibited greater adsorption capacity and adsorption density than gibbsite. And for both gibbsite and α-l2O3 , the maximum adsorption amount of phosphate was at pH 3.5 - 4.0. Therefore, information gained from surface properties examinations revealed that specific surface area played an important role on adsorption capacity, while the surface acidity of aluminol groups contributed more to adsorption affinity and consequent adsorption density.