钙改性玉米芯生物炭对水中氮磷吸附特性

以玉米芯为原材料，在500 ℃条件下高温热解制备生物炭，使用CaCl₂对其进行改性，通过SEM、EDS、BET-N₂、FTIR、XPS等手段对生物炭结构与组成进行了测定。通过吸附实验研究了改性生物炭对水中氮磷的吸附性能和影响因素，分析探讨其吸附机理，为生物炭在水处理中的应用提供参考依据。结果表明：CaCl₂改性使玉米芯生物炭比表面积提高了137.57%，微孔和介孔数增加，并产生Ca²⁺、Cl⁻离子有效附着。氮磷初始溶液质量浓度、固液比、吸附时间均会对生物炭的吸附性能产生影响。CaCl₂改性后的生物炭对氮磷吸附量分别提高了46.6%和78.4%。改性后的生物炭(Ca-BC)对水中氮磷的吸附更符合准二级动力学；Ca-BC对氨氮和磷酸盐的等温吸附更符合Langmuir模型，吸附过程更接近物理吸附为主，化学吸附为辅的单分子层吸附。Ca-BC通过范德华力静电相互作用、离子交换和化学沉淀过程去除水中氮磷。

Adsorption characteristics of calcium-modified corncob biochar for nitrogen and phosphorus in water

Biochar was prepared by pyrolysis of corn cob at 500 ℃. The biochar was modified by CaCl2. The structure and composition of biochar were determined by SEM、EDS、BET-N2、FTIR and XPS. The adsorption properties and influencing factors of modified biochar toward nitrogen and phosphorus in water were studied through the adsorption experiments, and the adsorption mechanism was analyzed, which will provide a reference for the application of biochar in water treatment. The results showed that the specific surface area of corncob biochar increased by 137.57%, the number of micro- and meso-pores increased, and Ca2+ and Cl− ions were effectively attached. All the initial solution concentration of nitrogen and phosphorus, the ratio of solid to liquid and the adsorption time affected the adsorption performance of biochar. The adsorption capacities of nitrogen and phosphorus of biochar modified by CaCl2 increased by 46.6% and 78.4%, respectively. The adsorption kinetic behaviors of nitrogen and phosphorus in water by modified biochar (Ca-BC) were consistent with the quasi-second-order kinetic model. The adsorption isotherms of ammonia nitrogen and phosphate by Ca-BC could be consistent with the Langmuir model, and the adsorption processes were close to the single molecular layer adsorption with physical adsorption as the main one and chemical adsorption as the auxiliary one. Ca-BC removed nitrogen and phosphorus from water through van der Waals electrostatic interaction, ion exchange and chemical precipitation processes.