Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Environ Sci Technol. 2010 Feb 15;44(4):1386-91. doi: 10.1021/es902946j.
Potable water treatment facilities may become an important barrier in limiting human exposure to engineered nanoparticles (ENPs) as ENPs begin to contaminate natural aquatic systems. Coagulation of ENPs will likely be a major process that controls the ENP fate and the subsequent removal in the aqueous phase. The influence that source water quality has on ENP coagulation is still relatively unknown. The current study uses a 2(3) x 2(4-1) fractional factorial design to identify seven key surface water constituents that affect multiwall carbon nanotube (MWCNT) coagulation. These seven factors include: influent concentrations of kaolin, organic matter (OM), alginate, and MWCNTs; type and dosage of coagulant; and method of MWCNT stabilization. MWCNT removal was most affected by coagulant type and dosage, with alum outperforming ferric chloride at circumneutral pH. None of the other factors were universally significant but instead depended on coagulant type, dose, and method of stabilization. In all cases where factors were found to have a significant impact on MWCNT removal, however, the relationship was consistent: higher influent concentrations of kaolin and alginate improved MWCNT removal while higher influent concentrations of OM hindered MWCNT coagulation. Once MWCNTs are released into the natural environment, their coagulation behavior will be determined by the type and quantity of pollutants (i.e., factors) present in the aquatic environment and are governed by the same mechanisms that influence the colloidal stability of "natural" nanoparticles.
饮用水处理设施可能成为限制人类接触工程纳米粒子 (ENPs) 的重要屏障，因为 ENPs 开始污染自然水生系统。ENPs 的混凝将可能是控制 ENP 命运和随后在水相中去除的主要过程。源水水质对 ENP 混凝的影响仍然相对未知。本研究使用 2(3) x 2(4-1) 部分析因设计来确定影响多壁碳纳米管 (MWCNT) 混凝的七个关键地表水成分。这七个因素包括：高岭土、有机物 (OM)、藻酸盐和 MWCNT 的进水浓度；混凝剂的类型和剂量；以及 MWCNT 的稳定方法。MWCNT 的去除受混凝剂类型和剂量的影响最大，在中性 pH 值下，明矾的性能优于氯化铁。其他因素都不是普遍重要的，而是取决于混凝剂类型、剂量和稳定方法。然而，在所有发现因素对 MWCNT 去除有显著影响的情况下，这种关系都是一致的：高岭土和藻酸盐的进水浓度越高，MWCNT 的去除效果越好，而 OM 的进水浓度越高，MWCNT 的混凝效果越差。一旦 MWCNTs 释放到自然环境中，它们的混凝行为将取决于水环境中存在的污染物（即因素）的类型和数量，并受影响“天然”纳米颗粒胶体稳定性的相同机制的控制。
