Sun Hang, Jiang Yu-Feng, Shi Lei-Ping, Mu Zhong-Feng, Zhan Hui-Ying
School of Environmental & Municipal Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China.
School of Chemical Engineering, Lanzhou University of Arts and Sciences, Lanzhou 730000, China.
Huan Jing Ke Xue. 2016 Dec 8;37(12):4857-4866. doi: 10.13227/j.hjkx.201606171.
The primary objective of this study was to investigate the effect of biochar, produced from maize and pine needles residue at different temperatures, on the adsorption of diuron onto loess soil. Meanwhile, the effect of the systemic temperature, pH values and the initial concentration of diuron were also investigated for the adsorption of diuron onto losses soil. And Kinetic parameters, such as rate constants, equilibrium adsorption capacities and related correlation coefficients were also calculated and discussed. The results showed that the adsorption of diuron onto loess soil by adding biochar could be described by the pseudo-second-order kinetic model, and followed the intraparticle diffusion model, but diffusion was not only the rate-controlling step. The adsorption process was divided into fast (0-8 h) and slow (8-12 h) adsorption stages, and equilibrium was reached at around 12 h. The adsorption thermodynamics of diuron onto loess soil was nonlinear by nature, and well fitted with the Freundlich isothermal model. Thermodynamic parameter analysis of diuron onto loess soil by adding biochar showed that Gibbs free energy (Δ) was less than zero, while Enthalpy (Δ) and Entropy (Δ) were greater than zero, indicating a spontaneous endothermic adsorption, which increased the degree of disorder during the process. And Thermodynamic parameter analysis of diuron onto loess soil without adding biochar showed that Gibbs free energy (Δ) and Entropy (Δ) were less than zero, while Enthalpy (Δ) was greater than zero. The average adsorption free energy was in range of 1.29-5.00 kJ·mol when the temperatures increased from 25 to 45℃, indicated that adsorption of diuron onto loess was a physical adsorption. The results also suggested that the influencing factors of diuron had significant effects on the adsorptive behaviors of diuron on loess soil. With increasing pyrolysis temperature of biochar, the equilibrium concentration of diuron in water decreased, while the amount of adsorption on loess soil increased. When the initial concentration of diuron increased from 0.5 mg·L to 6 mg·L, the adsorption capacity of diuron onto loess soil by adding biochar showed a rapidly increasing trend. When the initial concentration increased. the adsorption capacity showed a slow increasing trend and gradually tended to be stable. In the pH range of 3 to 10, the adsorption capacity of diuron onto loess soil by adding biochar changed a little.
本研究的主要目的是探究由玉米和松针残渣在不同温度下制备的生物炭对黄土吸附敌草隆的影响。同时，还研究了体系温度、pH值以及敌草隆初始浓度对黄土吸附敌草隆的影响。此外，还计算并讨论了动力学参数，如速率常数、平衡吸附容量及相关的相关系数。结果表明，添加生物炭后黄土对敌草隆的吸附可用准二级动力学模型描述，并符合颗粒内扩散模型，但扩散并非唯一的速率控制步骤。吸附过程分为快速（0 - 8小时）和慢速（8 - 12小时）吸附阶段，约12小时达到平衡。敌草隆在黄土上的吸附热力学本质上是非线性的，且与Freundlich等温模型拟合良好。添加生物炭后敌草隆在黄土上的热力学参数分析表明，吉布斯自由能（Δ）小于零，而焓（Δ）和熵（Δ）大于零，表明是自发吸热吸附，这增加了过程中的无序程度。未添加生物炭时敌草隆在黄土上的热力学参数分析表明，吉布斯自由能（Δ）和熵（Δ）小于零，而焓（Δ）大于零。当温度从25℃升高到45℃时，平均吸附自由能在1.29 - 5.00 kJ·mol范围内，表明敌草隆在黄土上的吸附是物理吸附。结果还表明，敌草隆的影响因素对敌草隆在黄土上的吸附行为有显著影响。随着生物炭热解温度的升高，水中敌草隆的平衡浓度降低，而在黄土上的吸附量增加。当敌草隆的初始浓度从0.5 mg·L增加到6 mg·L时，添加生物炭后黄土对敌草隆的吸附容量呈快速增加趋势。当初始浓度增加时，吸附容量呈缓慢增加趋势并逐渐趋于稳定。在pH值为3至10的范围内，添加生物炭后黄土对敌草隆的吸附容量变化不大。
