添加生物炭对西北黄土吸附克百威的影响

研究了不同温度下制得的生物炭对西北黄土吸附农药克百威的影响,并对溶液p H值和初始浓度对吸附的影响进行了探讨.结果表明,克百威在添加生物炭黄土上的动力学吸附过程较好地符合准二级吸附动力学模型;热力学吸附较好地符合Freundlich等温吸附模型;随着系统温度的升高,添加生物炭的黄土对克百威的吸附量增大,且其对克百威的吸附自由能变(ΔGθ)小于0,吸附焓变(ΔHθ)及吸附熵变(ΔSθ)均大于0,表明吸附是一个自发吸热且体系混乱程度增大的等温吸附过程.溶液p H值和克百威的初始浓度对添加生物炭的土样吸附影响较明显.当p H值为4~7时,添加生物炭的土样饱和吸附量随p H升高呈缓慢降低,当p H值大于7时,吸附容量随p H升高呈明显降低趋势.克百威初始浓度从20 mg·L-1增至50 mg·L-1的过程中,吸附量快速上升,初始浓度大于50 mg·L-1时,吸附量随初始浓度的升高而缓慢增加并逐渐趋于平衡.

Adsorption and influential factors of carbofuran on the loess soil by adding biochar prepared at different temperatures

The primary objective of this study was to investigate the effect of biochar produced from wheat residue at different temperatures on the adsorption of carbofuran by loess soil.The impact of pH values and initial concentrations on the adsorption process were also identified.Kinetic parameters,such as rate constants, equilibrium adsorption capacities and related correlation coefficients were calculated and discussed. The results showed that the adsorption of carbofuran onto loess soil by adding biochar could be described by the pseudo-second-order kinetic model and followed the intraparticle diffusion model.The adsorption equilibrium of carbofuran was reached within 10 h. The adsorption thermodynamics of carbofuran onto loess soil is nonlinear by nature, and well fitted with the Freundlich isothermal model. Thermodynamics parameters such as the change of free energy, enthalpy and entropy were also evaluated for the adsorption of carbofuran onto loess soil by adding biochar, indicating a spontaneous endothermic adsorption, which increases the degree of chaos in process. At the pH in a range of 4 to 7, the adsorption capacity of carbofuran onto loess soil by adding biochar showed a slow decreasing trend, while the decreasing trend become more significant when pH was greater than 7. When the initial concentration of carbofuran increased from 20 mg·L^-1 to 50 mg·L^-1, the adsorption capacity of carbofuran onto loess soil by adding biochar showed a rapidly increasing trend, while the initial concentration of carbofuran greater than 50 mg·L^-1, the adsorption capacity showed a slow increasing trend and gradually reached balance.