白云石矿物对水溶液中Cu2+、Pb2+吸附的动力学和热力学

采用静态实验方法研究了白云石对水溶液中Cu2+、Pb2+的吸附特性,通过批实验考察了反应时间、溶液初始浓度、pH值、离子强度、温度以及固液比等因素对吸附的影响,探讨了白云石对Cu2+、Pb2+的吸附动力学、热力学规律及其反应机制。实验结果显示:白云石对Cu2+、Pb2+的吸附在24 h达到平衡,对Pb2+的吸附量大于Cu2+,伪二级和双常数动力学方程分别能较好地拟合白云石对Cu2+、Pb2+的吸附;在一定条件下,白云石对Cu2+、Pb2+的去除率与溶液初始浓度呈反比,与固液比呈正比;吸附等温方程符合Langmuir模型,为单分子层吸附;溶液pH值对吸附行为影响显著,在溶液pH=6~7时,吸附效果最好,离子强度对吸附影响甚微;白云石对Cu2+、Pb2+的吸附属于吸热反应,反应自发进行,高温促进白云石的吸附行为。

Kinetics and thermodynamics of Cu2+ and Pb2+ adsorption from aqueous solutions onto dolomite adsorbent

In this research, a static experimental method was applied for Cu2+ and Pb2+ removal from aqueous solution using dolomite adsorbent. The process was investigated in terms of contact time, initial concentration, pH, ionic strength, temperature, and solid contents by the batch experiments. To elucidate the reaction mechanism, the experimental data were analyzed using equilibrium isotherm, and kinetic and thermodynamic models. The results showed that the adsorption equilibrium time for both ions was 24 h and the maximum adsorption capacity for Pb2+ was larger than that for Cu2+. Kinetic data of Cu2+ and Pb2+ adsorption on dolomite accurately fitted the pseudo-second order and double-exponential kinetic models, respectively. Under certain conditions, the Cu2+ and Pb2+ adsorption on dolomite was inversely proportional to the initial concentrations, and directly proportional to the solid-liquid ratio. Furthermore, the isotherm data were well described by the Langmuir isotherm model, indicating that the adsorption of Cu2+ and Pb2+ on dolomite was a monolayer adsorption process. Effective removal of metal ions was demonstrated at pH 6 to 7. Ionic strength was not the main factor influencing the reaction. The results also showed that the adsorption processes of both ions were spontaneous and endothermic, promoted by high temperatures.