Laboratory of Water, Energy and Environment, National School of Engineers, University of Sfax, Sfax 1173-3038, Tunisia.
J Environ Manage. 2012 Jan;93(1):245-53. doi: 10.1016/j.jenvman.2011.08.002. Epub 2011 Oct 19.
Effects of impurities on the removal of heavy metals by natural limestones in aqueous solutions were studied by evaluating various factors including limestone concentration, pH, contact time and temperature. Solutions of Pb(II), Cd(II), Cu(II) and Zn(II), prepared from chloride reagents at a concentration of 10 mg/L, were studied in a batch method. Four natural limestone samples, collected from the Campanian-Maastrichtian limestone beds in Tunisia, were used as adsorbents. Sorption experiments indicated that high removal efficiencies could be achieved. Limestone samples containing impurities, such as silica, iron/aluminum oxides and different kinds of clay minerals, demonstrated enhanced sorption capacity, nearing 100% removal in some cases. Kinetic experiments showed that the sorption of metal ions occurred rapidly at a low coverage stage, and that solutions were nearly at equilibrium after 60 min. Data trends generally fit pseudo-second order kinetic, and intra-particle diffusion, models. The following conditions were found to promote optimum, or near-optimum, sorption of heavy metals: 1) contact time of more than 60 min, 2) pH = 5, 3) >3 g/L limestone concentration and 4) T = 35 °C. The results of this study suggest that the limestones from northern Tunisia, that contain higher amounts of silica and iron/aluminum oxides, are promising adsorbents for the effective removal of toxic heavy metals from wastewaters.
研究了杂质对水溶液中天然石灰石去除重金属的影响，评估了包括石灰石浓度、pH 值、接触时间和温度在内的各种因素。采用批处理法，用浓度为 10mg/L 的氯化试剂制备了 Pb(II)、Cd(II)、Cu(II)和 Zn(II)溶液。采用来自突尼斯坎潘-马斯特里赫特石灰岩床的四种天然石灰石作为吸附剂进行了吸附实验。实验结果表明，高去除效率可以实现。含有杂质（如二氧化硅、铁/铝氧化物和不同类型的粘土矿物）的石灰石样品表现出增强的吸附能力，在某些情况下接近 100%的去除率。动力学实验表明，金属离子的吸附在低覆盖阶段迅速发生，并且在 60 分钟后溶液几乎达到平衡。数据趋势通常符合拟二级动力学和内扩散模型。发现以下条件有利于重金属的最佳或接近最佳吸附：1）接触时间超过 60 分钟，2）pH = 5，3）>3g/L 石灰石浓度和 4）T = 35°C。本研究结果表明，含有更多二氧化硅和铁/铝氧化物的突尼斯北部石灰石是从废水中有效去除有毒重金属的有前途的吸附剂。
