College of Architecture and Environment, Sichuan University, Chengdu, 610065, China.
College of Architecture and Environment, Sichuan University, Chengdu, 610065, China; National Engineering Research Center for Flue Gas Desulfurization, Chengdu, 610065, China.
Chemosphere. 2021 Sep;279:130514. doi: 10.1016/j.chemosphere.2021.130514. Epub 2021 Apr 8.
This study proposed a simple and green air oxidation (AO) method to prepare hierarchical porous biochar by selectively removing lignin carbon from biochar after the pyrolysis of plant-based biomass, based on the fact that the thermal decomposition temperature in air between lignin carbon and cellulose/hemicellulose carbon was different. Three kinds of biomass with different lignocellulose contents were used, including walnut shell, cypress sawdust and rice straw. The results found that AO treatment could effectively improve the pore structure of the three biochar. The specific surface area of WCO-4, CCO-4 and RCO-4 was 555.0 m/g, 418.7 m/g and 291.9 m/g, respectively, which was significantly higher than those of WC (319.5 m/g), CC (381.7 m/g) and RC (69.6 m/g), respectively. Among these, walnut shell biochar with air oxidation (WCO) had higher surface area of 555.0 m/g and mesopore volume of 0.116 cm/g, this was related to its high content of lignin, which could facilitate the formation of mesopores by AO treatment with high selectivity. The toluene adsorption capacity of WCO reached 132.9 mg/g, which increased by 223.4% from that without AO treatment. The kinetics study indicated that the diffusion rates of toluene molecule were improved due to the increased mesopores volume of biochar and micropores also play an important role in the adsorption of toluene. The results demonstrate that AO treatment is a promising method to develop hierarchical porous structure for lignocellulose-rich plant-based biomass with low cost and environmental-friendly, which greatly enhanced the toluene adsorption capacity.
本研究提出了一种简单绿色的空气氧化（AO）方法，通过在植物生物质热解后选择性地从生物炭中去除木质素碳，来制备分级多孔生物炭，这是基于木质素碳和纤维素/半纤维素碳在空气中的热分解温度不同的事实。本研究使用了三种木质纤维素含量不同的生物质，包括核桃壳、柏木锯末和稻草。结果发现，AO 处理可以有效地改善三种生物炭的孔结构。WCO-4、CCO-4 和 RCO-4 的比表面积分别为 555.0 m/g、418.7 m/g 和 291.9 m/g，明显高于 WC（319.5 m/g）、CC（381.7 m/g）和 RC（69.6 m/g）。其中，经空气氧化（WCO）处理的核桃壳生物炭的比表面积更高，为 555.0 m/g，介孔体积为 0.116 cm/g，这与其较高的木质素含量有关，高选择性的 AO 处理有利于介孔的形成。WCO 的甲苯吸附量达到 132.9 mg/g，比未经 AO 处理时增加了 223.4%。动力学研究表明，由于生物炭中介孔体积的增加，甲苯分子的扩散速率得到了提高，微孔也在甲苯的吸附中起着重要作用。结果表明，AO 处理是一种很有前途的方法，可以开发低成本、环保的富含木质素的植物生物质的分级多孔结构，极大地提高了甲苯的吸附能力。
