Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China; Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA.
Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA; Institute of Costal Environmental Pollution Control, and Ministry of Education Key Laboratory of Marine Environment and Ecology, Ocean University of China, Qingdao 266100, China.
Sci Total Environ. 2016 Oct 1;566-567:50-56. doi: 10.1016/j.scitotenv.2016.04.204. Epub 2016 May 20.
Adsorption and bioaccessibility of phenanthrene on graphite and multiwalled carbon nanotubes (CNTs) were investigated in simulated gastrointestinal fluid using a passive dosing system. The saturated adsorption capacity of phenanthrene on different adsorbents follows an order of hydroxylated CNTs (H-CNTs)>carboxylated CNTs (C-CNTs)>graphitized CNTs (G-CNTs)>graphite, consistent with the order of their surface area and micropore volume. The change of phenanthrene adsorption on the adsorbents is different with the presence of pepsin (800mg/L) and bile salts (500mg/L and 5000mg/L, abbreviated as BS500 and BS5000). Both solubilization of phenanthrene by pepsin and bile salts and their competition with phenanthrene for the adsorption sites play a role. In addition, the large increase of the maximum adsorption capacity in BS5000 solution indicates an enhanced dispersion of CNTs or an exfoliation of graphite by bile salts, which consequently increases the exposed surface area. The bioaccessibility increases in pepsin and BS500 solution with a growing free phenanthrene concentration. Although the bioaccessibility of phenanthrene stalls or slightly decreases in the middle range of free phenanthrene concentration in BS5000 solution, the bioaccessibility overall is much higher than that in pepsin and BS500 solution at the same phenanthrene level. It is impossible to separate the effect of competition from dispersion (or exfoliation) at this stage, but the relative contribution of solubilization to phenanthrene desorption in pepsin and BS500 solutions was quantified, which improves our understanding of the mechanisms on bioaccessibility of adsorbed pollutants on CNTs.
采用被动投加系统，研究了在模拟胃肠道液体中，多壁碳纳米管（CNTs）和石墨对菲的吸附和生物可给性。菲在不同吸附剂上的饱和吸附容量顺序为：羟基化 CNT（H-CNTs）＞羧基化 CNT（C-CNTs）＞石墨化 CNT（G-CNTs）＞石墨，这与它们的表面积和微孔体积顺序一致。在胃蛋白酶（800mg/L）和胆盐（500mg/L 和 5000mg/L，缩写为 BS500 和 BS5000）存在的情况下，菲在吸附剂上的吸附变化不同。胃蛋白酶和胆盐对菲的增溶作用及其与菲对吸附位点的竞争均起作用。此外，BS5000 溶液中最大吸附容量的大幅增加表明，胆盐增强了 CNT 的分散或石墨的剥离，从而增加了暴露的表面积。在胃蛋白酶和 BS500 溶液中，生物可给性随游离菲浓度的增加而增加。尽管在 BS5000 溶液中游离菲浓度的中间范围内，生物可给性停滞或略有下降，但在相同菲浓度下，BS5000 溶液中的生物可给性远高于胃蛋白酶和 BS500 溶液中的生物可给性。在现阶段，无法将竞争的效果与分散（或剥离）的效果分开，但对胃蛋白酶和 BS500 溶液中菲解吸的增溶作用的相对贡献进行了定量，这提高了我们对 CNTs 上吸附污染物生物可给性机制的理解。
