Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, København Ø, Denmark.
Environ Sci Technol. 2020 Mar 17;54(6):3643-3652. doi: 10.1021/acs.est.9b07069. Epub 2020 Mar 6.
Biochars function as electron transfer mediators and thus catalyze redox transformations of environmental pollutants. A previous study has shown that bone char (BC) has high catalytic activity for reduction of chlorinated ethylenes using layered Fe(II)-Fe(III) hydroxide (green rust) as reductant. In the present study, we studied the rate of trichloroethylene (TCE) reduction by green rust in the presence of BCs obtained at pyrolysis temperatures (PTs) from 450 to 1050 °C. The reactivity increased with PT, yielding a maximum pseudo-first-order rate constant () of 2.0 h in the presence of BC pyrolyzed at 950 °C, while no reaction was seen for BC pyrolyzed at 450 °C. TCE sorption, specific surface area, extent of graphitization, carbon content, and aromaticity of the BCs also increased with PT. The electron-accepting capacity (EAC) of BC peaked at PT of 850 °C, and EAC was linearly correlated with the sum of concentrations of quinoid, quaternary N, and pyridine-N-oxide groups measured by XPS. Moreover, no TCE reduction was seen with graphene nanoparticles and graphitized carbon black, which have high degrees of graphitization but low EAC values. Further analyses showed that TCE reduction rates are well correlated with the EAC and the C/H ratio (proxy of electrical conductivity) of the BCs, strongly indicating that both electron-accepting functional groups and electron-conducting domains are crucial for the BC catalytic reactivity. The present study delineates conditions for designing redox-reactive biochars to be used for remediation of sites contaminated with chlorinated solvents.
生物炭作为电子转移介质，因此可以催化环境污染物的氧化还原转化。先前的研究表明，骨炭 (BC) 具有使用层状 Fe(II)-Fe(III) 氢氧化物（绿色锈）作为还原剂还原氯代乙烯的高催化活性。在本研究中，我们研究了在 450 至 1050°C 热解温度下获得的 BC 的存在下，绿色锈还原三氯乙烯 (TCE) 的速率。反应性随热解温度升高而增加，在 950°C 热解的 BC 存在下，得到最大的拟一级速率常数 (kobs) 为 2.0 h，而在 450°C 热解的 BC 则没有反应。BC 的 TCE 吸附、比表面积、石墨化程度、碳含量和芳构化程度也随热解温度升高而增加。BC 的电子接受能力 (EAC) 在 850°C 的热解温度下达到峰值，并且 EAC 与通过 XPS 测量的醌型、季氮和吡啶-N-氧化物基团浓度之和呈线性相关。此外，具有高石墨化程度但 EAC 值较低的石墨烯纳米粒子和石墨化炭黑均未观察到 TCE 还原。进一步的分析表明，TCE 还原速率与 BC 的 EAC 和 C/H 比（电导率的代理）密切相关，强烈表明电子接受官能团和电子传导域对于 BC 的催化活性至关重要。本研究描绘了设计用于修复含氯溶剂污染场地的氧化还原反应性生物炭的条件。
