西北黄土对克百威的吸附特征

采用批量试验的方法研究了西北地区黄土对克百威的吸附动力学和热力学行为,并对相关影响因素进行了分析。结果表明:黄土对克百威吸附的最优动力学方程为准二级动力学方程;克百威在黄土中的吸附较好地符合Freundlich等温吸附方程;黄土吸附克百威过程中的吉布斯自由能ΔG■、焓变ΔH■及熵变ΔS■都小于0,表明黄土对克百威的吸附为自发进行的放热过程,并且吸附过程中体系混乱度减小,黄土吸附克百威的主要作用力为氢键力;pH值为4~10时,随pH值增大克百威的吸附容量减小,且pH值为4~8时减小趋势较平缓,p H值为8~10时减小趋势很大;随供试土样粒径减小,克百威在黄土中的吸附容量增大,当土壤粒径从0.45 mm减小到0.075 mm时,吸附容量由0.009 mg/g增加到0.049 mg/g;克百威在黄土中的吸附容量受其初始质量浓度影响很大,随克百威初始质量浓度增大,黄土对其的吸附容量相应增加,克百威初始质量浓度从20 mg/L增至110mg/L时,其在黄土中的吸附容量从0.080 mg/g增加至0.206 mg/g。

Study on the adsorption behavior of carbofuran onto loess soil in Northwest China

This paper intends to provide a batch of experimental results for identifying and determining the absorption kinetics and the thermodynamics processes of carbofuran to the loess soil through a case study sample in the northwest area of China.In the said experiment,we have undergone a series of physical,chemical and biological experiments in hoping to observe and identify the adsorption/desorption process for the pesticides to make clear of their effects on the loess soil.At the same time,we have also made an investigation of the effects of the systemic temperature,pH value and the initial concentration of carbofuran on the adsorption of carbofuran to the losses soil.Thus,the results of our investigation indicate that it is better to present the adsorption kinetic effects of the carbofuran on the losses soil via a pseudo-second-order model,which is involved with the boundary layer control and intraparticle diffusion in the aforementioned process.The results of our investigation also demonstrate that the thermodynamic adsorption status in situ of the said carbofuran on the loess soil proves to be nonlinear by nature,which is well in accord with the Freundlich isothermal model.Furthermore,the thermodynamic parameters of the Gibbs free energy (△G(☉)),the enthalpy (△H(☉)),and the entropy (△S(☉)) tend to reveal the spontaneous nature of the following adsorption processes,such as the exothermic adsorption and the decreasing randomness at the solid-solution interface due to the adsorption of carbofuran.In addition,the analysis of enthalpy (△H(☉)) can help to reveal the hydrogen bond due to the driving force of carbofuran absorption onto loess soil.What is more,the pH value,the particle size and the initial concentration of carbofuran may all have significant effects on the adsorption behaviors of carbofuran for the loess soil,whose adsorption intensity turns to be decreased with the increase of pH value from 4 to 10.When the particle size of loess soil decreases from 0.425 mm to 0.075 mm,the absorption capacity of carbofuran would be increasing from 0.009 mg/g to 0.049 mg/g.Besides,when the initial concentration of the carbofuran has increased from 20 mg/L to 110 mg/L,the adsorption capacity of the carbofuran may increase from 0.080 mg/g to 0.206 mg/g.