Department of Applied Geology, Faculty of Earth Sciences, Hydrogeology, Kharazmi University, Tehran, Iran.
Department of Applied Geology, Faculty of Earth Sciences, Hydrogeology, Kharazmi University, Tehran, Iran.
Sci Total Environ. 2018 Jun 1;626:995-1004. doi: 10.1016/j.scitotenv.2018.01.184. Epub 2018 Feb 19.
Carbon nanoparticles such graphene, carbon nanotubes, and carbon dots offer the potential to improve environmental treatment technologies due to their unique properties such as low toxicity and high metal sorption capacity. However, there are no studies on facilitated transport and remobilization of pre-sorbed metals by carbon dot (CD) nanoparticles in quartz sand columns. Here, we investigate the effects of solution ionic strength (IS; 1, 100 and 200 mM NaCl) and pH (Chen et al., 2017; Chen et al., 2010; Cornell and Schwertmann, 2006), initial CD concentration (200, 400, 600 and 800 mg L), and clay content (10, 20 and 30%w kaolinite) in quartz sand columns on the transport, retention and remobilization of Cu and Pb in saturated (upward flow) quartz porous media. Batch sorption experiments were employed to underpin the findings of the column transport experiments. Both CD and quartz adsorbed Cu and Pb from water, but adsorption was higher on CD than quartz. Co-transport experiment demonstrated the CD-facilitated transport of Cu and Pb. Sequential transport experiments (first three phases) demonstrated the retention of Cu and Pb in the quartz column, with higher retention of Pb compared to Cu. The Cu and Pb retention was attributed to their sorption on the quartz grains and precipitation under the experimental conditions investigated in this study. Cu retention increased with the increase in ionic strength, pH and clay content. Pb was nearly totally retained in the quartz column at all experimental conditions. The subsequent injection of CD resulted in Cu and Pb remobilization to different extents, except in the presence of high kaolinite concentration. CD is most efficient in remobilizing Cu and Pb at 400 mg L CD concentration and under low ionic strength (ca. 1-100 mM), low pH (ca. 6) and in the absence of clays. Deviation from these conditions results in reduced remobilization of Cu and Pb.
碳纳米粒子，如石墨烯、碳纳米管和碳点，由于其低毒性和高金属吸附能力等独特性质，有望改善环境处理技术。然而，目前还没有研究报道碳点（CD）纳米粒子在石英砂柱中促进预吸附金属的迁移和再移动。在这里，我们研究了溶液离子强度（IS；1、100 和 200 mM NaCl）和 pH 值（Chen 等人，2017 年；Chen 等人，2010 年；Cornell 和 Schwertmann，2006 年）、初始 CD 浓度（200、400、600 和 800 mg/L）和粘土含量（10、20 和 30%w 高岭土）对 Cu 和 Pb 在饱和（向上流动）石英多孔介质中迁移、保留和再移动的影响。批处理吸附实验用于支持柱传输实验的结果。CD 和石英都从水中吸附 Cu 和 Pb，但 CD 的吸附量高于石英。共迁移实验证明了 CD 促进了 Cu 和 Pb 的迁移。顺序传输实验（前三个阶段）表明 Cu 和 Pb 在石英柱中被保留，Pb 的保留率高于 Cu。Cu 和 Pb 的保留归因于它们在实验条件下吸附在石英颗粒上并沉淀下来。Cu 的保留率随离子强度、pH 值和粘土含量的增加而增加。在所有实验条件下，Pb 几乎完全保留在石英柱中。随后注入 CD 导致 Cu 和 Pb 不同程度的再移动，除了高高岭土浓度存在的情况。在 CD 浓度为 400 mg/L、离子强度低（约 1-100 mM）、pH 值低（约 6）且不存在粘土的情况下，CD 最有效地再移动 Cu 和 Pb。偏离这些条件会导致 Cu 和 Pb 的再移动减少。
