Methods of using carbon nanotubes as filter media to remove aqueous heavy metals
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Although carbon nanotubes (CNTs) are well known to have a strong affinity to various heavy metals in aqueous solution, little research has been dedicated to exploit their use in fixed-bed water treatment systems (e.g., trickling filters). In this work, batch sorption and fixed-bed experiments were conducted to examine the ability of functionalized multi-walled CNTs as filter media to remove two heavy metal ions (Pb2+ and Cu2+) from infiltrating water. Batch sorption experiments confirmed the strong sorption affinity of the CNTs for Pb2+ and Cu2+ in both single and dual metal solution systems. In addition, sonication-promoted dispersion of the CNT particles enhanced their heavy metal sorption capacity by 23.9–32.2%. For column experiments, laboratory-scale fixed-bed columns were packed with CNTs and natural quartz sand by three different packing: layered, mixed, and deposited. While all the three packing methods enhanced the fixed-bed filtering efficiency of Pb2+ and Cu2+ from single and dual metal systems, the CNT-deposited packing method was superior. Although the amount of the CNTs added into the fixed-bed columns was only 0.006% (w/w) of the sand, they significantly improved the fixed-bed’s filtering efficiency of Pb2+ and Cu2+ by 55–75% and 31–57%, respectively. Findings from this study demonstrate that functionalized multi-walled CNTs, together with natural sand, can be used to effectively and safely remove heavy metals from water.
Tian, Y., et al. 2012. Methods of using carbon nanotubes as filter media to remove aqueous heavy metals. Chemical Engineering Journal. 210: pp.557-563. Available from http://dx.doi.org/10.1016/j.cej.2012.09.015