[Adsorption Characteristics of Phosphate in an Aqueous Solution by Swine Manure Biochar]

To solve the problem of phosphate pollution in water and achieve the resource utilization of livestock and poultry manure biomass, swine manure was selected as the raw material to prepare biochar. The composition and structure of SMBC700 were characterized using elemental analysis, specific surface area analysis, and FTIR. The adsorption isotherm model and adsorption kinetics model were used to fit the phosphate adsorption characteristics of swine manure biochar, and the effects of pyrolysis temperature, biochar dosing, initial solution pH, and coexisting ions on phosphate adsorption by biochar were studied. The conditions affecting phosphate adsorption were optimized by response surface methodology （RSM）. The results showed that only SMBC700 could adsorb phosphate. The phosphate adsorption capacity of SMBC700 reached 6.127 1 mg·g^-1 at a SMBC700 dosage of 2 g·L^-1 and the initial phosphate concentration of 20 mg·L^-1. The adsorption isotherm and kinetics were better fitted by the Langmuir isotherm model and the pseudo second-order kinetics. SMBC700 exhibited an excellent performance for phosphate adsorption over a wide pH range （3-12）. The coexistence of HCO₃^- could significantly weaken the adsorption capacity of SMBC700 to phosphate. The optimum conditions for phosphate adsorption by SMBC700 were obtained by RSM analysis with a dosage of 3 g·L^-1, an initial phosphate concentration of 30 mg·L^-1, and a pH of 7.0. The possible mechanisms of phosphate adsorption by SMBC700 included electrostatic adsorption, ligand exchange, and pore filling.