Denison Sara B, Jin Peixuan, Dias Da Silva Priscilla, Chu Chun, Moorthy Bhagavatula, Senftle Thomas P, Zygourakis Kyriacos, Alvarez Pedro J J
Department of Civil and Environmental Engineering, Rice University, Houston, Texas 77005, United States.
Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States.
Environ Sci Technol. 2023 Sep 26;57(38):14373-14383. doi: 10.1021/acs.est.3c04487. Epub 2023 Sep 8.
Transition metal catalysts can significantly enhance the pyrolytic remediation of soils contaminated with polycyclic aromatic hydrocarbons (PAHs). Significantly higher pyrene removal efficiency was observed after the pyrolytic treatment of Fe-enriched bentonite (1.8% wt ion-exchanged content) relative to natural bentonite or soil (i.e., 93% vs 48% and 4%) at the unprecedentedly low temperature of 150 °C with only 15 min treatment time. DFT calculations showed that bentonite surfaces with Fe or Cu adsorb pyrene stronger than surfaces with Zn or Na. Enhanced pyrene adsorption results from increased charge transfer from its aromatic π-bonds to the cation site, which destabilizes pyrene allowing for faster degradation at lower temperatures. UV-Vis and GC-MS analyses revealed pyrene decomposition products in extracts of samples treated at 150 °C, including small aromatic compounds. As the pyrolysis temperature increased above 200 °C, product distribution shifted from extractable compounds to char coating the residue particles. No extractable byproducts were detected after treatment at 400 °C, indicating that char was the final product of pyrene decomposition. Tests with human lung cells showed that extracts of samples pyrolyzed at 150 °C were toxic; thus, high removal efficiency by pyrolytic treatment does not guarantee detoxification. No cytotoxicity was observed for extracts from Fe-bentonite samples treated at 300 °C, inferring that char is an appropriate treatment end point. Overall, we demonstrate that transition metals in clay can catalyze pyrolytic reactions at relatively low temperatures to decrease the energy and contact times required to meet cleanup standards. However, mitigating residual toxicity may require higher pyrolysis temperatures.
过渡金属催化剂可以显著增强对受多环芳烃（PAHs）污染土壤的热解修复效果。在仅15分钟的处理时间、前所未有的低温150℃下，对富铁膨润土（离子交换含量为1.8%重量）进行热解处理后，芘的去除效率显著高于天然膨润土或土壤（即93%对48%和4%）。密度泛函理论计算表明，含有铁或铜的膨润土表面比含有锌或钠的表面对芘的吸附更强。芘吸附增强是由于其芳香π键向阳离子位点的电荷转移增加，这使芘不稳定，从而在较低温度下能更快降解。紫外可见光谱和气相色谱 - 质谱分析揭示了在150℃处理的样品提取物中有芘分解产物，包括小分子芳香化合物。随着热解温度升至200℃以上，产物分布从可提取化合物转变为覆盖残留颗粒的炭。在400℃处理后未检测到可提取的副产物，表明炭是芘分解的最终产物。对人肺细胞的测试表明，在150℃热解的样品提取物具有毒性；因此，热解处理的高去除效率并不能保证解毒。在300℃处理的铁膨润土样品提取物未观察到细胞毒性，这表明炭是合适的处理终点。总体而言，我们证明了粘土中的过渡金属可以在相对较低温度下催化热解反应，以降低达到清理标准所需的能量和接触时间。然而，减轻残留毒性可能需要更高的热解温度。
