PDF(Pubmed)
Abstract：
Groundwater contamination by 1,2,3-trichloropropane (TCP) poses a unique challenge due to its human toxicity and recalcitrance to degradation. Previous work suggests that nitrogenous functional groups of pyrogenic carbonaceous matter (PCM), such as biochar, are important in accelerating contaminant dechlorination by sulfide. However, the reaction mechanism is unclear due, in part, to PCM\'s structural complexity. Herein, PCM-like polymers (PLPs) with controlled placement of nitrogenous functional groups [i.e., quaternary ammonium (QA), pyridine, and pyridinium cations (py+)] were employed as model systems to investigate PCM-enhanced TCP degradation by sulfide. Our results suggest that both PLP-QA and PLP-py+ were highly effective in facilitating TCP dechlorination by sulfide with half-lives of 16.91 ± 1.17 and 0.98 ± 0.15 days, respectively, and the reactivity increased with surface nitrogenous group density. A two-step process was proposed for TCP dechlorination, which is initiated by reductive ß-elimination, followed by nucleophilic substitution by surface-bound sulfur nucleophiles. The TCP degradation kinetics were not significantly affected by cocontaminants (i.e., 1,1,1-trichloroethane or trichloroethylene), but were slowed by natural organic matter. Our results show that PLPs containing certain nitrogen functional groups can facilitate the rapid and complete degradation of TCP by sulfide, suggesting that similarly functionalized PCM might form the basis for a novel process for the remediation of TCP-contaminated groundwater.
摘要：
1,2,3-三氯丙烷（TCP）对地下水的污染由于其对人类的毒性和对降解的顽固性而提出了独特的挑战。以前的工作表明，热解含碳物质（PCM）的含氮官能团，比如生物炭，在加速硫化物对污染物的脱氯过程中具有重要意义。然而,反应机理尚不清楚，在某种程度上,PCM的结构复杂性。在这里，含氮官能团的受控放置的PCM样聚合物(PLPs)[即，季铵（QA），吡啶,和吡啶阳离子（py）]用作模型系统，以研究硫化物对PCM增强的TCP降解。我们的结果表明，PLP-QA和PLP-py在促进硫化物对TCP脱氯方面非常有效，半衰期为16.91±1.17和0.98±0.15天，分别,反应性随着表面含氮基团密度的增加而增加。提出了TCP脱氯的两步过程，这是由还原性β-消除引发的，然后用表面结合的硫亲核试剂进行亲核取代。TCP降解动力学不受共污染物的显著影响(即，1,1,1-三氯乙烷或三氯乙烯)，但是被天然有机物减慢了速度。我们的结果表明，含有某些氮官能团的PLPs可以促进硫化物对TCP的快速和完全降解，表明类似的功能化PCM可能构成修复TCP污染地下水的新方法的基础。
