生物炭颗粒的分级提取、表征及其对磺胺甲噁唑的吸附性能研究

Fractionated extraction and characterization of biochar and its adsorption behavior for sulfamethoxazole

以玉米秸秆为原料,在不同温度条件下(300~600℃)制备生物炭,并对生物炭进行粒径分级(50~250μm,5~50μm,1~5μm,<1.0μm).通过比表面积测定仪、透射电镜、纳米粒度仪、X射线光电子能谱对不同粒径生物炭的理化特性进行表征;并以粗粒径(50~250μm)生物炭为对照,探讨生物炭胶体颗粒对典型有机污染物磺胺甲噁唑(SMX)的吸附性能.结果表明:生物炭胶体颗粒比粗粒径生物炭具有更大的比表面积以及更发达的微孔结构,且随着制备温度的升高,生物炭胶体颗粒的比表面积和孔容提高更加显著;生物炭胶体颗粒表面含有更多的含氧官能团以及矿质元素;生物炭胶体颗粒对SMX的等温吸附曲线能够用Freundlich吸附方程较好地拟合,表明吸附过程可能为异质性表面吸附,且吸附能力显著强于粗粒径生物炭.以上结果表明,生物炭胶体颗粒具有独特的理化特性,因而在环境中可能参与更多的生物地球化学过程;此外,其对有机污染物具有更强的吸附能力,加之较强的迁移特性,很有可能作为载体促进污染物在水土环境中的迁移转化.因此,在充分利用生物炭改土固碳的同时,有必要关注其可能引起的环境风险.

Biochars were produced from corn stalks under different temperatures （300～600℃）, and then the biochar particles were fractionated into four size ranges （50～250 μm, 5～50 μm, 1～5 μm, 〈1.0 μm）. The fractionated biochar particles were characterized using N2 adsorption/desorption, transmission electron microscope, dynamic light scattering and X-ray photoelectron spectroscopy. The adsorption capacity of sulfamethoxazole （SMX）, a typical organic contaminant, on biochar colloids was also investigated with bulk biochar （50～250 μm） as a control sample. The results show that biochar colloids had larger BET surface area and well-developed microporosity than bulk biochars. Moreover, with increasing temperature for biochar production, BET surface area and pore volume of biochar colloids were enhanced more significantly. The biochar colloids had more oxygen containing groups and mineral elements on carbon surface. The adsorption isotherms for SMX could be well fitted by Freundlich model, implying that the adsorption probably occurred on heterogeneous surfaces. The adsorption capacity of biochar colloids was significantly higher than that of bulk biochars. These results demonstrate that biochar colloids have unique physical and chemical properties compared with bulk biochars, and thus likely to participate in more biogeochemical processes in the environment. Additionally, due to the strong adsorption capacity and migration property, biochar colloids would probably become carrier for pollutants to promote their transfer and transformation in the water/soil environments. Therefore, it is necessary to pay attention to the potential risks of biochars when they are widely used in improving soil quality and carbon sequestration.