School of Hydraulic and Environmental Engineering, Changsha University of Science & Technology, Changsha 410114, China.
School of Hydraulic and Environmental Engineering, Changsha University of Science & Technology, Changsha 410114, China; College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082, China.
Sci Total Environ. 2022 Jul 20;831:154754. doi: 10.1016/j.scitotenv.2022.154754. Epub 2022 Mar 24.
Nanoscale zerovalent iron (nZVI) represents a promising reduction technology for water remediation, but its broad application is largely hampered by the tendency of nZVI to aggregate and the low electron transferability due to the interfacial charge resistance. Herein, by combining the advantages of polypyrrole (PPY) and nZVI, we prepared a composite material (i.e., PPY supported palladium‑iron bimetallic nanoparticles (Pd/Fe@PPY)) and applied it for the simultaneous removal of 4-chlorophenol (4-CP) and Cr(VI). Our results showed that this material had superior catalytic performances with a complete removal of 4-CP (50 mg·L) and Cr(VI) (10 mg·L) within 60 and 1 min, respectively. As opposed to the bare Pd/Fe nanoparticles, the reactivity of Pd/Fe@PPY with 4-CP was significantly enhanced by nearly 8 times. The enhanced catalytic activity of Pd/Fe@PPY was attributed to the distinctive properties of PPY as i) a good support that resulted in the formation of Pd/Fe nanoparticles with high dispersibility; ii) an adsorbent that increased the accessibility of 4-CP and Cr(VI) with electrons or active species (e.g., H*) on the particles surface; iii) an electron transfer carrier that facilitated the reactivity of Pd/Fe@PPY with contaminants by reducing the interfacial charge resistance. Moreover, by conducting cyclic voltammetry and quenching investigations, we showed that two mechanisms (i.e., direct and H*-mediated indirect electron transfer) were involved in the reductive dehalogenation of 4-CP, while catalytic hydrodechlorination played a dominant role. This work offers an alternative material for the efficient removal of 4-CP and Cr(VI) and provides better understanding of the relationship between structure and catalytic activity of nZVI.
纳米零价铁（nZVI）代表了一种有前途的水修复还原技术，但由于 nZVI 易于聚集以及界面电荷电阻导致电子转移能力低，其广泛应用受到了很大的限制。在此，通过结合聚吡咯（PPY）和 nZVI 的优势，我们制备了一种复合材料（即，负载钯-铁双金属纳米粒子的 PPY（Pd/Fe@PPY）），并将其用于同时去除 4-氯苯酚（4-CP）和 Cr(VI)。结果表明，该材料具有优异的催化性能，可在 60 秒和 1 分钟内分别完全去除 50 mg·L 的 4-CP 和 10 mg·L 的 Cr(VI)。与裸 Pd/Fe 纳米粒子相比，Pd/Fe@PPY 与 4-CP 的反应性显著提高了近 8 倍。Pd/Fe@PPY 的增强催化活性归因于 PPY 的独特性质：i）作为良好的载体，导致 Pd/Fe 纳米粒子具有高分散性；ii）作为吸附剂，增加了电子或活性物质（例如，H*）在粒子表面上对 4-CP 和 Cr(VI)的可及性；iii）作为电子转移载体，通过降低界面电荷电阻，促进 Pd/Fe@PPY 与污染物的反应性。此外，通过进行循环伏安法和猝灭研究，我们表明两种机制（即直接和 H*-介导的间接电子转移）参与了 4-CP 的还原脱卤反应，而催化加氢脱氯则起主导作用。这项工作为高效去除 4-CP 和 Cr(VI)提供了一种替代材料，并提供了对 nZVI 结构与催化活性之间关系的更好理解。
