鸟粪石晶体吸附Cu(II)的热力学和动力学特征分析及机制探讨

摘要

本文采用基于液相原位调控合成的鸟粪石晶体材料开展了对Cu(II)的吸附研究.基于吸附热力学及动力学分析,揭示了鸟粪石晶体对Cu(II)吸附行为及相关机理.合成的鸟粪石晶体材料属斜方晶系,颗粒表面分布有较多孔隙、狭缝,比表面积为23.42 m2/g.热力学分析表明,鸟粪石晶体材料在pH 4.0及318 K条件下对Cu(II)的饱和吸附量为145.1 mg/g;吸附动力学分析表明,吸附过程符合准二级动力学模型.经计算可得其吸附活化能Ea为17.5 kJ/mol,表明吸附过程属于化学吸附.此外,进行了包括吉布斯自由能变ΔGads、焓变ΔHads、熵变ΔSads在内的热力学计算,结果表明鸟粪石晶体吸附Cu(II)过程属于自发、吸热反应.基于对鸟粪石晶体材料吸附前、后的表征,发现过程中表面静电引力及配位作用促进了铜离子在鸟粪石表面的吸附,并且发现鸟粪石晶体材料在表面及裂缝中存在有铜离子向氢氧化铜的转变行为.%Synthesized struvite was innovatively applied to removing Cu(II) from aqueous solution. The Cu(II) adsorption behavior and relative mechanisms were studied and analyzed. The maximum Cu(II) adsorption under pH=4.0 and 318 K calculated from adsorption thermodynamic analysis was 145.1 mg/g. The sorption kinetics can be favorably described by pseudo-second order model. The activation energy (Ea) of 17.5 kJ/mol suggested that the adsorption process was a chemical adsorption. The calculated thermodynamic parameters indicated that the adsorption was a spontaneous and endothermic one. On the basis of characterization upon struvite before and after adsorption, it was found that the electrostatic attraction and coordination bonding supported the ion sorption on struvite surface, and the transformation of copper ion into copper hydroxide occurred on struvite surface and within its crevices.