硝基苯在米草湿地土壤中的吸附特征

Adsorption Characteristics of Nitrobenzene in the Spartina Wetland Soil

为全面了解硝基苯在米草湿地土壤中的吸附特征,考察了土壤pH、温度等对湿地土壤吸附硝基苯的影响。结果表明,硝基苯在湿地土壤中的吸附平衡时间为6 h,其吸附的动力学过程可以用Lagergren一级动力学方程很好的拟合,相关系数(R2)为0.9156。Freundlich方程是最适合描述湿地土壤吸附硝基苯行为的等温式,相关系数(R2)为0.9397。硝基苯在湿地土壤中的吸附主要是物理吸附,其吸附热为-18.47 kJ mol-1,氢键力是吸附的主要作用力。硝基苯在有机质上吸附自由能的改变量为-19.38kJ mol-1,标准自由能的变小是硝基苯在土壤有机质上吸附的推动力。土壤对硝基苯的吸附量随温度的升高而减少,随pH的降低而增加,即当环境温度较高、环境溶液为碱性时,硝基苯在土壤上的吸附都会受到抑制。

To comprehensively understand the adsorption behaviors of nitrobenzene in the Spartina wetland soil, adsorption experiments were to be done and the influences of temperature and pH were investigated. The results showed that the adsorption equilibrium was reached in 6 h, and the kinetic cures were fit to Lagergren equation. The correlation coefficient R2 was 0.9156. Freundlich isotherm was the most suitable to describe the behaviors of nitrobenzene in the wetland soil and its correlation coefficient R2 was 0.9397. The adsorption of nitrobenzene to the wetland soil is dominated by the partition of physical adsorption, and △H° = - 18.47 kJ mol^-1 suggested that the hydrogen bonds were the main forces of the adsorption. The free energy change was - 19.38 kJ mol^-1,which is the driving force of nitrobenzene to the soil organic matter. The nitrobenzene adsorptive capacity of the wetland soil decreased gradually with temperature ascension and increased with the decrease of pH, that is, the adsorption was inhibited in high temperature and alkaline conditions.