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.
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