Beijing Key Laboratory of Water Resources and Environmental Engineering, School of Water Resources and Environment, China University of Geosciences, Beijing, 100083, China; Northwest Engineering Corporation Limited, Xi'an, 710065, China.
Beijing Key Laboratory of Water Resources and Environmental Engineering, School of Water Resources and Environment, China University of Geosciences, Beijing, 100083, China.
Chemosphere. 2021 Dec;284:131223. doi: 10.1016/j.chemosphere.2021.131223. Epub 2021 Jun 22.
Humic substances (HSs) have great retention effects on pentachlorophenol (PCP) migration in subsurface environment, but the adsorption mechanism of PCP by HSs with various aromatic/aliphatic moieties and acidic functional groups in the presence of Cr(VI) is still unclear. In this study, the adsorption mechanism of PCP by undissolved humic acid (HA) and humin (HM) extracted from peat, black soil, lignite and coal was investigated under the presence of Cr(VI). According to the results, HA samples had much lower adsorption capacity for hydrophobic PCP than HM samples due to their higher contents of hydrophilic polar oxygen-containing functional groups. In respect to PCP adsorption mechanism, the molecular unsaturation of HSs associated with humification degree was found to be the determinant instead of polarity. Notably, after reacting with Cr(VI), significant decreasing of PCP adsorption quantities occurred on HSs extracted from lignite and coal with higher degrees of unsaturation (H/C < 0.64), while HSs extracted from peat and black soil with lower degrees of unsaturation (H/C > 0.83) kept almost unchanged, which can be attributed to the much higher reactivity of aromatic domains of HSs for Cr(VI) reduction compared with aliphatic moieties. This indicated that the adsorption mechanism of PCP by HSs with higher and lower degrees of unsaturation might be respectively driven by π-π interaction and hydrophobic interaction. This study highlighted the diverse adsorption mechanisms of PCP on HSs with different degrees of humification, and emphasized the coexisting Cr(VI) only have significant effect on PCP adsorption by HSs with higher humification degrees instead of the lower ones.
腐殖质（HSs）对五氯苯酚（PCP）在地下环境中的迁移具有很强的保留作用，但在 Cr(VI) 存在下，具有各种芳基/脂肪结构和酸性官能团的 HSs 对 PCP 的吸附机制仍不清楚。在这项研究中，研究了在 Cr(VI) 存在下，从泥炭、黑土、褐煤和煤中提取的未溶解腐殖酸（HA）和腐殖质（HM）对 PCP 的吸附机制。结果表明，由于亲水性极性含氧官能团含量较高，HA 样品对疏水性 PCP 的吸附能力远低于 HM 样品。就 PCP 的吸附机制而言，发现 HSs 的分子不饱和性与腐殖化程度有关，而不是极性。值得注意的是，与 Cr(VI) 反应后，H/C < 0.64 的不饱和程度较高的褐煤和煤中提取的 HSs 对 PCP 的吸附量显著降低，而 H/C > 0.83 的不饱和程度较低的泥炭和黑土中提取的 HSs 几乎保持不变，这归因于 HSs 的芳香结构对 Cr(VI)还原的反应性远高于脂肪结构。这表明，具有较高和较低不饱和程度的 HSs 对 PCP 的吸附机制可能分别由π-π相互作用和疏水相互作用驱动。本研究强调了不同腐殖化程度的 HSs 对 PCP 的吸附机制的多样性，并强调了共存的 Cr(VI) 仅对腐殖化程度较高的 HSs 对 PCP 的吸附有显著影响，而对腐殖化程度较低的 HSs 没有影响。
