Ministry of Education Key Laboratory of Humid Subtropical Eco-Geographical Process, Fujian Provincial Key Laboratory for Plant Eco-Physiology, College of Geographical Science, Fujian Normal University, Fuzhou, Fujian 350007, China.
Ministry of Education Key Laboratory of Humid Subtropical Eco-Geographical Process, Fujian Provincial Key Laboratory for Plant Eco-Physiology, College of Geographical Science, Fujian Normal University, Fuzhou, Fujian 350007, China.
Sci Total Environ. 2019 Nov 25;693:133455. doi: 10.1016/j.scitotenv.2019.07.261. Epub 2019 Jul 22.
Currently, it is still lack of systematic and in-depth knowledge regarding the co-effect of carbon-based fractions and ash in the sorption behavior of biochars. Therefore, pristine wood-derived biochars (PBCs) produced at different temperatures and their corresponding de-ashed versions (DBCs) were used to determine the roles of carbon's morphological structure and ash in sorption of aromatic compounds (toluene, m-toluidine, and m-nitrotoluene) to biochars. The results showed that biochars produced at 300-400 °C (mainly uncarbonized organic matter, UCOM) and 900 °C (turbostratic carbon, TC) may have stronger partition effect and pore filling effect with π-π interaction, respectively, and thus have greater sorption coefficients (Lg K) than biochars produced at 600 °C (pyrogenic amorphous carbon, PAC), which are probably dominated by surface hydrophobic effect. Meanwhile, TC had a greater Lg K than UCOM at low adsorbate concentrations (C), but exhibited an opposite trend at high C. The Lg K values of DBCs are always greater than those of PBCs, indicating ash has an inhibitory effect on sorption of aromatic compounds to biochars. Furthermore, the role of ash in sorption behavior of PBCs would vary with solution pH. At a neutral pH, PBCs have the maximum sorption quantity for aromatic compounds due to the formed cation-π bond between cations of ash and aromatic compounds. However, the acidic pH enhanced the dissolution of cations in ash and the basic pH enhanced the hydroxylation of cations in ash. Therefore, both acidic and basic pH weakened the cation-π bond between ash and aromatic compounds and decreased the sorption of aromatic compounds on PBCs. The results suggest that de-ashed biochars with more UCOM or TC are effective sorbents for sequestration of aromatic compounds, and provide a well-designed method for improving the sorption efficiency of biochars.
目前，对于碳质分馏物和灰分在生物炭吸附行为中的协同作用，仍缺乏系统和深入的了解。因此，使用不同温度下制备的原始木质衍生生物炭（PBC）及其相应的去灰版本（DBC）来确定碳形态结构和灰分在芳香族化合物（甲苯、间甲苯胺和间硝基甲苯）吸附到生物炭中的作用。结果表明，在 300-400°C（主要为未碳化的有机物质，UCOM）和 900°C（乱层石墨碳，TC）下制备的生物炭可能分别通过π-π相互作用具有更强的分配效应和孔填充效应，因此具有更大的吸附系数（Lg K），而在 600°C（热解无定形碳，PAC）下制备的生物炭则可能主要受表面疏水性效应的影响。同时，在低吸附物浓度（C）下，TC 的 Lg K 大于 UCOM，但在高 C 下则表现出相反的趋势。DBC 的 Lg K 值始终大于 PBC 的 Lg K 值，表明灰分对芳香族化合物吸附到生物炭上有抑制作用。此外，灰分在 PBC 吸附行为中的作用会随溶液 pH 值而变化。在中性 pH 值下，由于灰分中的阳离子与芳香族化合物之间形成了阳离子-π键，因此 PBC 对芳香族化合物的吸附量最大。然而，酸性 pH 值增强了灰分中阳离子的溶解，而碱性 pH 值增强了灰分中阳离子的羟化。因此，酸性和碱性 pH 值都削弱了灰分与芳香族化合物之间的阳离子-π键，降低了芳香族化合物在 PBC 上的吸附。研究结果表明，具有更多 UCOM 或 TC 的去灰生物炭是有效吸附剂，可以用于芳烃的捕获，并为提高生物炭的吸附效率提供了一种设计良好的方法。
