CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei 230026, China.
Department of Environmental Sciences, The Connecticut Agricultural Experiment Station, 123 Huntington St., P.O. Box 1106, New Haven, Connecticut 06504-1106, United States.
Environ Sci Technol. 2021 Oct 5;55(19):13072-13081. doi: 10.1021/acs.est.1c04748. Epub 2021 Sep 24.
This study examined conditions that mimic oxidative processes of biomass chars during formation and weathering in the environment. A maple char prepared at the single heat treatment temperature of 500 °C for 2 h was exposed to different thermal oxidation conditions or accelerated oxidative aging conditions prior to sorption of naphthalene or the dication paraquat. Strong chemical oxidation (SCO) was included for comparison. Thermal oxidation caused micropore reaming, with ambient oxidation and SCO much less so. All oxidative treatments incorporated O, acidity, and cation exchange capacity (CEC). Thermal incorporation of O was a function of headspace O concentration and reached a maximum at 350 °C due to the opposing process of burn-off. The CEC was linearly correlated with O/C, but the positive intercept together with nuclear magnetic resonance data signifies that, compared to O groups derived by anoxic pyrolysis, O acquired through oxidation by thermal or ambient routes contributes more to the CEC. Thermal oxidation increased the naphthalene sorption coefficient, the characteristic energy of sorption, and the uptake rate due to pore reaming. By contrast, ambient oxidation (and SCO) suppressed naphthalene sorption by creating a more hydrophilic surface. Paraquat sorption capacity was predicted by an equation that includes a CEC term due to bidentate interaction with pairs of charges, predominating over monodentate interaction, plus a term for the capacity of naphthalene as a reference representing nonspecific driving forces.
本研究考察了在形成和风化过程中模拟生物质炭氧化过程的条件。一种在 500°C 单一热解温度下处理 2 小时制得的枫木炭，在萘或二价百草枯吸附之前，分别经历了不同的热氧化条件或加速氧化老化条件。同时还包括了强化学氧化（SCO）进行对比。热氧化导致微孔扩孔，而环境氧化和 SCO 的作用则较小。所有氧化处理都包含 O、酸度和阳离子交换容量（CEC）。O 的热掺入是由顶部空间 O 浓度决定的，在 350°C 达到最大值，这是由于燃烧过程的相反作用。CEC 与 O/C 呈线性相关，但正截距加上核磁共振数据表明，与缺氧热解产生的 O 基团相比，通过热或环境途径氧化获得的 O 对 CEC 的贡献更大。热氧化通过扩孔增加了萘的吸附系数、吸附特征能量和吸附速率。相比之下，环境氧化（和 SCO）通过创造更亲水的表面抑制了萘的吸附。由于双齿相互作用与电荷对的结合，百草枯的吸附容量可以通过包含 CEC 项的方程来预测，这主要是因为双齿相互作用，而不是单齿相互作用，再加上萘的容量作为代表非特异性驱动力的参考。
