Department of Environmental Science, Zhejiang University, Hangzhou, 310058, China.
Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Zhejiang University, Hangzhou, 310058, China.
Environ Sci Pollut Res Int. 2020 May;27(15):18412-18422. doi: 10.1007/s11356-020-08291-5. Epub 2020 Mar 18.
Biochar (BC) colloids attract increasing interest due to their unique environmental behavior and potential risks. However, the interaction between BC colloids and organic contaminants that may affect their fates in the environment has not been substantially studied. Herein, adsorption and desorption of phenanthrene (PHN), atrazine (ATZ), and oxytetracycline (OTC) by a series of BC colloids derived from bulk rice straw BC samples with 6 pyrolysis temperatures (200-700 °C), and 3 particle sizes (250 nm, 500 nm, and 1 μm) were investigated. Regardless of pyrolysis temperature, BC colloids from a given sized bulk BC had a comparable size, being 30 ± 6, 70 ± 18, and 140 ± 15 nm corresponding to the three sized bulk BCs, respectively. The adsorption kinetics curves were well explained by the pseudo-second-order model, and pore diffusion was the primary rate-determining step. Both Freundlich and Langmuir models well fitted the adsorption isotherms. With increasing pyrolysis temperature or decreasing particle size of bulk BC, the specific surface area and pore volumes of the derived BC colloids increased, the kinetics model fitted adsorption rates (k) of the three organics by the BC colloids all largely decreased, and the Langmuir model fitted adsorption capacities (Q) increased. The highest Q was obtained by BC colloids from the smallest (250 nm) bulk BC with the highest pyrolysis temperature (700 °C), being 212 μmol g for PHN, 815 μmol g for ATZ, and 72.4 μmol g for OTC. The adsorption was reversible for PHN and ATZ, while significant desorption hysteresis was observed for OTC on BC colloids with middle pyrolysis temperatures (300-500 °C). The underlying mechanisms including hydrophobic interaction, π-π electron donor-acceptor interaction, molecular size effect, and irreversible reactions were discussed to explain the difference in the adsorption and desorption behaviors. The findings increased our understanding of the environmental fate and risk of BC.
生物炭胶体由于其独特的环境行为和潜在风险而引起越来越多的关注。然而，生物炭胶体与有机污染物之间的相互作用，可能会影响它们在环境中的归宿，这方面的研究还不够充分。在此，通过一系列源自不同热解温度（200-700°C）和 3 种粒径（250nm、500nm 和 1μm）的大块稻秆生物炭的生物炭胶体，研究了菲（PHN）、莠去津（ATZ）和土霉素（OTC）在这些胶体上的吸附和解吸作用。无论热解温度如何，源自同一粒径的大块生物炭的生物炭胶体具有相近的粒径，分别为 30±6nm、70±18nm 和 140±15nm。吸附动力学曲线很好地用拟二级动力学模型解释，并且孔扩散是主要的速率决定步骤。Freundlich 和 Langmuir 模型都很好地拟合了吸附等温线。随着热解温度的升高或大块生物炭粒径的减小，所得生物炭胶体的比表面积和孔体积增加，动力学模型拟合的三种有机物被生物炭胶体吸附的速率（k）均大幅降低，Langmuir 模型拟合的吸附容量（Q）增加。在所有热解温度和粒径条件下，由最小粒径（250nm）和最高热解温度（700°C）的大块生物炭制备的生物炭胶体对 PHN 的吸附量最高，为 212μmol/g；对 ATZ 的吸附量最高，为 815μmol/g；对 OTC 的吸附量最高，为 72.4μmol/g。PHN 和 ATZ 的吸附是可逆的，而在中等热解温度（300-500°C）下，OTC 在生物炭胶体上的解吸存在明显的滞后现象。讨论了包括疏水性相互作用、π-π 电子给体-受体相互作用、分子尺寸效应和不可逆反应在内的潜在机制，以解释吸附和解吸行为的差异。这些发现增进了我们对生物炭环境归宿和风险的理解。
