Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Institute of Physicochemical and Biological Problems in Soil Science, RAS, Pushchino, Moscow Region 142290, Russia.
J Hazard Mater. 2022 Jun 5;431:128637. doi: 10.1016/j.jhazmat.2022.128637. Epub 2022 Mar 5.
Manganese oxides (Mn oxides) are ubiquitous and may coexist with Fe(III) ions in soil environments. In this study, acid birnessite, alkaline birnessite, cryptomelane, pyrolusite, manganite, and their Fe(III)-modified analogues were synthesized and used for benzo(a)pyrene transformation. Fe-modified Mn oxides show a markedly enhanced transformation capability towards benzo(a)pyrene. Specifically, the benzo(a)pyrene transformation rate constants k for Bir-H, Bir-OH, Cry, Pyr, and Man were 0.49, 0.080, 0.0071, 0.0055, and 0.0022 h, respectively. After Fe(III) modification, the transformation rate constants were increased to 22, 2.7, 0.25, 0.0072 and 0.0098 h, respectively. Fe(III)-modified layered birnessites exhibited better activity than Fe(III)-modified tunnel Mn oxides, which was attributed to their high Fe(III) contents and abundant active free radicals. Fe(III) was found to accept electrons from benzo(a)pyrene, thereby accelerating the benzo(a)pyrene transformation. Moreover, modification with Fe(III) increased the surface adsorbed water and oxygen, and promoted the generation of active free radicals. Finally, the physicochemical and biochemical properties of transformation products showed the environmental benefits of this process. Overall, the results indicate that the occurrence of Fe(III) ions could promote the removal of PAHs in Mn oxides-rich soils, and this study provides a credible understanding of PAH fates in natural soils.
锰氧化物（Mn 氧化物）普遍存在，可能与土壤环境中的 Fe(III) 离子共存。在这项研究中，酸型钠锰矿、堿性钠锰矿、钙锰矿、软锰矿、菱锰矿及其 Fe(III) 修饰类似物被合成并用于苯并(a)芘的转化。Fe 修饰的 Mn 氧化物对苯并(a)芘表现出明显增强的转化能力。具体来说，Bir-H、Bir-OH、Cry、Pyr 和 Man 的苯并(a)芘转化速率常数 k 分别为 0.49、0.080、0.0071、0.0055 和 0.0022 h。经 Fe(III)修饰后，转化速率常数分别提高到 22、2.7、0.25、0.0072 和 0.0098 h。Fe(III)修饰的层状钠锰矿表现出比 Fe(III)修饰的隧道型 Mn 氧化物更好的活性，这归因于其高的 Fe(III)含量和丰富的活性自由基。Fe(III)被发现从苯并(a)芘中接受电子，从而加速了苯并(a)芘的转化。此外，Fe(III)修饰增加了表面吸附水和氧，并促进了活性自由基的生成。最后，转化产物的物理化学和生化性质表明了该过程的环境效益。总的来说，结果表明，Fe(III)离子的存在可以促进富含 Mn 氧化物土壤中 PAHs 的去除，本研究为自然土壤中 PAH 命运提供了可信的理解。
