生物质粒径对负载MgO生物炭吸附水体中磷的影响

为研究生物质粒径对负载MgO芦苇生物炭（MBC）去除水体中磷的速率和能力的影响，以0~0.5、1~2和6~8 mm这3种不同粒径的芦苇颗粒为原料、MgCl₂为改性剂制备MBC，用傅里叶变换红外光谱仪（FTIR）、X射线衍射仪（XRD）和扫描电子显微镜（SEM）等对MBC表征，开展MBC吸附溶液中磷酸盐（PO₄^3--P）动力学和等温线实验以及实验数据模型拟合.结果表明，MBC对溶液中PO₄^3--P的吸附速率随生物质粒径增大而增大，0~0.5、1~2和6~8 mm芦苇颗粒制备的MBC对PO₄^3--P的吸附量在2 h内分别达到平衡吸附量的15.4%、25.8%和80.8%，而生物质粒径对MBC的PO₄^3--P最大吸附量（249.0~254.7 mg·g^-1）无明显影响.6~8 mm芦苇颗粒制备的MBC保留了较完整的芦苇细胞壁结构，且含有丰富的微孔和中孔，形成多层次、规则的、连通性好的孔隙结构.0~0.5 mm和1~2 mm芦苇颗粒制备的MBC孔隙结构较差，孔隙连通性受损，影响了磷酸根离子在MBC内部的扩散速率，限制了对磷的吸附速率.因此，以人工湿地收割的废弃植物芦苇为原料制备MBC用于去除水体中磷时，将芦苇破碎至6~8 mm即可，过度破碎会破坏MBC的孔隙结构，减小MBC对磷的去除速率.

Effect of Biomass Particle Size on the Adsorption of Phosphorus from Aqueous Solution by MgO-loaded Biochar

To study the effect of biomass particle size on the rate and ability of phosphorus removal from aqueous solution by MgO-loaded Phragmites australis biochar (MBC), MBC was prepared using 0.0-0.5, 1.0-2.0, and 6.0-8.0 mm Phragmites australis particles as the feedstock and MgCl₂ as the modification material. The MBC was characterized using FTIR, XRD, and SEM techniques. Kinetic and isotherm experiments of phosphate (PO₄^3--P) adsorption from aqueous solution by the MBC were conducted, and the experimental data were fitted with various kinetic and isotherm models. The results showed that the adsorption rate of PO₄^3--P by the MBC increased with the increase in biomass particle size. The amount of PO₄^3--P adsorbed by the MBC prepared from 0.0-0.5, 1.0-2.0, and 6.0-8.0 mm particles reached 15.4%, 25.8%, and 80.8%, respectively, within 2 h. The biomass particle size did not affect the maximum PO₄^3--P adsorption capacity (249.0-254.7 mg·g^-1) of the MBC. MBC prepared from the 6-8 mm particles retained the complete cell wall structure of the Phragmites australis, and a large number of micropores and mesopores were generated during pyrolysis, thereby forming a hierarchical, regular, and well-connected pore structure. MBC prepared from the 0.0-0.5 mm and 1.0-2.0 mm particles had inferior pore structures with inferior pore connectivity, which affected the diffusion rate of PO₄^3- ions inside the MBC and limited the PO₄^3--P adsorption rate. Therefore, when using waste Phragmites australis harvested from a constructed wetland to produce MBC and remove phosphorus from water, the Phragmites australis should be crushed into 6-8 mm particles. Over-crushing deteriorates the pore structure of the produced MBC and reduces the removal rate of phosphorus by the MBC.