摘要
Biochar is a potential carrier for nutrients due to its porous nature and abundant functional groups. However, raw biochar has a limited or even negative capacity to adsorb phosphate. To enhance phosphate removal and reduce phosphate releases, acidic, alkaline, and surfactant pretreatments, followed by granulation and ferric oxide loading, were applied to raw biochar powder (Bp). The alkaline pretreatment proved to be the most effective method and exhibited significant pore expansion and surface oxidation. Bg-OH-FO showed the highest phosphate removal efficiency at 99.2% (initial phosphate concentration of 20 mg/L) after granulation and ferric oxide loading. Static adsorption results indicated that a pH value of 4 was the most suitable for phosphate adsorption because of the surface properties of Bg-OH-FO and the distribution of P (V) in water. Higher temperatures and a larger initial phosphate concentration led to better adsorption; the adsorption capacity of Bg-OH-FO was 1.91 mg/g at 313 K with an initial phosphate concentration of 50 mg/L. The Bg-OH-FO adsorption process was endothermic in nature. The Freundlich model seemed to be the optimum isotherm model for Bg-OH-FO. Under continuous adsorption, the flow rate and bed depth were changed to optimize the operation conditions. The results indicate that a slow flow rate and high bed depth helped increase the removal efficiency (η) of the fixed bed. The breakthrough curves fitted well with the Yoon–Nelson model. © 2017, Tianjin University and Springer-Verlag GmbH Germany.
Biochar is a potential carrier for nutrients due to its porous nature and abundant functional groups. However, raw biochar has a limited or even negative capacity to adsorb phosphate. To enhance phosphate removal and reduce phosphate releases, acidic, alkaline, and surfactant pretreatments,followed by granulation and ferric oxide loading, were applied to raw biochar powder(B_p). The alkaline pretreatment proved to be the most effective method and exhibited significant pore expansion and surface oxidation. B_g-OH-FO showed the highest phosphate removal efficiency at 99.2%(initial phosphate concentration of 20 mg/L) after granulation and ferric oxide loading. Static adsorption results indicated that a p H value of 4 was the most suitable for phosphate adsorption because of the surface properties of B_g-OH-FO and the distribution of P(V) in water. Higher temperatures and a larger initial phosphate concentration led to better adsorption; the adsorption capacity of B_g-OH-FO was 1.91 mg/g at 313 K with an initial phosphate concentration of 50 mg/L. The B_gOH-FO adsorption process was endothermic in nature. The Freundlich model seemed to be the optimum isotherm model for B_g-OH-FO. Under continuous adsorption, the flow rate and bed depth were changed to optimize the operation conditions. The results indicate that a slow flow rate and high bed depth helped increase the removal efficiency(g) of the fixed bed. The breakthrough curves fitted well with the Yoon–Nelson model.
基金
supported by the National key research and development program (No. 2016YFC0401107)
the National Natural Science Foundation of China (No. 21577068)
