Department of Civil and Environmental Engineering, University of South Carolina, Columbia, SC 29201, USA.
Water Res. 2011 Jul;45(13):4056-68. doi: 10.1016/j.watres.2011.05.015. Epub 2011 May 27.
In this study, the adsorption of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) from landfill leachate onto single-walled carbon nanotubes (SWCNTs) was investigated. Different leachate solutions were prepared by altering the pH, ionic strength, and dissolved organic carbon (DOC) in the solutions to mimic the varying water conditions that occur in leachate during the various stages of waste decomposition. The youngest and oldest leachate solutions contained varying DOC and background chemistry and were represented by leachate Type A (pH = 5.0; DOC = 2500 mg/L; conductivity = 12,500 μS/cm; [Ca(2+)] = 1200 mg/L; [Mg(2+)] = 470 mg/L) and Type E (pH = 7.5; DOC = 250 mg/L; conductivity = 3250 μS/cm; [Ca(2+)] = 60 mg/L; [Mg(2+)] = 180 mg/L). These solutions were subsequently combined in different ratios to produce intermediate solutions, labeled B-D, to replicate time-dependent changes in leachate composition. Overall, a larger fraction of EE2 was removed as compared to BPA, consistent with its higher log K(OW) value. The total removal of BPA and EE2 decreased in older leachate solutions, with the adsorptive capacity of SWCNTs decreasing in the order of leachate Type A > Type B > Type C > Type D > Type E. An increase in the pH from 3.5 to 11 decreased the adsorption of BPA by 22% in young leachate and by 10% in old leachate. The changes in pH did not affect the adsorption of EE2 in the young leachate, but did reduce adsorption by 32% in the old leachate. Adjusting the ionic strength using Na(+) did not significantly impact adsorption, while increasing the concentration of Ca(2+) resulted in a 12% increase in the adsorption of BPA and a 19% increase in the adsorption of EE2. DOC was revealed to be the most influential parameter in this study. In the presence of hydrophilic DOC, represented by glucose in this study, adsorption of the endocrine disrupting compounds (EDCs) onto the SWCNTs was not affected. In the absence of SWCNTs, hydrophobic DOC (i.e., humic acid) adsorbed 15-20% of BPA and EE2. However, when the humic acid and SWCNTs were both present, the overall adsorptive capacity of the SWCNTs was reduced. Hydrophobic (π-π electron donor-acceptor) interactions between the EDCs and the constituents in the leachate, as well as interactions between the SWCNTs and the EDCs, are proposed as potential adsorption mechanisms for BPA and EE2 onto SWCNTs.
在这项研究中，研究了单壁碳纳米管（SWCNTs）对垃圾渗滤液中双酚 A（BPA）和 17α-乙炔雌二醇（EE2）的吸附。通过改变 pH 值、离子强度和溶液中的溶解有机碳（DOC）来制备不同的渗滤液溶液，以模拟在废物分解的不同阶段渗滤液中发生的变化的水质条件。最年轻和最古老的渗滤液溶液含有不同的 DOC 和背景化学物质，分别由渗滤液类型 A（pH=5.0；DOC=2500mg/L；电导率=12500μS/cm；[Ca(2+)]=1200mg/L；[Mg(2+)]=470mg/L）和类型 E（pH=7.5；DOC=250mg/L；电导率=3250μS/cm；[Ca(2+)]=60mg/L；[Mg(2+)]=180mg/L）表示。随后，将这些溶液以不同的比例混合，以产生中间溶液，标记为 B-D，以复制渗滤液成分随时间的变化。总体而言，与 EE2 相比，BPA 的去除比例更大，这与其更高的 log K（OW）值一致。在较老的渗滤液溶液中，BPA 和 EE2 的总去除率降低，SWCNTs 的吸附能力顺序为渗滤液类型 A＞类型 B＞类型 C＞类型 D＞类型 E。将 pH 值从 3.5 增加到 11 会使年轻渗滤液中 BPA 的吸附减少 22%，使老渗滤液中的吸附减少 10%。pH 值的变化对年轻渗滤液中 EE2 的吸附没有影响，但使老渗滤液中的吸附减少 32%。使用 Na(+) 调整离子强度对吸附没有显著影响，而增加 Ca(2+)的浓度会使 BPA 的吸附增加 12%，EE2 的吸附增加 19%。DOC 被揭示是本研究中最具影响力的参数。在亲水 DOC（本研究中代表葡萄糖）存在的情况下，内分泌干扰化合物（EDCs）不会吸附到 SWCNTs 上。在没有 SWCNTs 的情况下，疏水性 DOC（即腐殖酸）吸附了 15-20%的 BPA 和 EE2。然而，当腐殖酸和 SWCNTs 都存在时，SWCNTs 的整体吸附能力会降低。EDCs 与渗滤液中成分之间的疏水性（π-π 电子供体-受体）相互作用以及 SWCNTs 与 EDCs 之间的相互作用被提出是 BPA 和 EE2 吸附到 SWCNTs 上的潜在吸附机制。
