苯多羧酸分子标志物对生物炭吸附磷行为的表征

Characterization of phosphorus adsorption behaviors by biochar with benzene polycarboxylic acid molecular biomarkers

生物炭因其具有多孔、比表面积较大、含氧官能团较为丰富且芳香性较强等优点而在农业面源污染控制方面具有良好的应用前景。然而,生物炭应用于土壤后难以从土壤颗粒中分离出来,从而制约了其对农业面源污染物吸附行为的预测。分子标志物技术在表征有机碳行为领域做出了重要的贡献,苯多羧酸(Benzene polycarboxylic acids,BPCAs)分子标志物方法的引入,可为表征生物炭与磷之间相互作用提供新的视角。因此,本研究采用批量吸附实验,考察了烟秆和松木及其制备的生物炭对磷的吸附行为。结果表明,随热解温度的升高,生物质及其生物炭中各BPCAs含量及苯六甲酸(Benzene hexacarboxylic acid,B6CA)对BPCA的贡献率随热解温度的升高而增加,生物炭的芳香缩合度不断增强;两类生物炭对磷的吸附量均随热解温度的升高而降低,其中400℃烟秆生物炭和200℃松木生物炭对磷的吸附量最大。表面含氧官能团的减少和静电排斥作用降低了生物炭对磷的吸附,而较大的比表面积使烟秆生物炭的吸附量高于松木生物炭。烟秆生物炭中B6CA含量高于松木生物炭,因此其对磷的吸附量较松木生物炭高。

Biochar has good applications in agricultural non-point pollution control owing to its porous,large specific surface area,rich oxygen-containing functional groups,and strong aromaticity.However,biochar is difficult to separate from soil particles after its application to soil,limiting the prediction of adsorption behaviors of biochar to agricultural non-point source pollutants.Molecular biomarker technology has made important contributions to the understanding of organic carbon behavior,and the benzene polycarboxylic acid(BPCAs)molecular biomarker method may provide a new perspective for understanding the interactions between biochar and phosphorus.In this study,batch experiments were carried out to investigate the adsorption behaviors of tobacco stalk,pine wood,and their derived biochars.Results showed that the content of BPCAs and the contribution rate of mellitic acid to BPCAs increased with an increase in pyrolysis temperature of biomass and biochar.The content of each BPCA and the contribution rate of benzene hexacarboxylic acid(B6CA)to BPCA increases with an increase in pyrolysis temperature.The degree of aromatic condensation of biochar continued to increase.The amount of phosphorus adsorbed by biochar decreased with an increase in pyrolysis temperature.Biochar from tobacco stalk had the largest adsorption capacity for phosphorus at 400℃,while biochar from pine wood had the largest adsorption capacity at 200℃.The decrease in surface oxygen-containing functional groups and the increase in electrostatic repulsion negatively affected the adsorption capacity of the biochars.Adsorption capacity of biochar from tobacco stalk was higher than that of biochar from pine for the former larger specific surface area and higher content of B6CA.