高温焙烧改性混凝污泥对氨氮的吸附特性

Ammonia-nitrogen adsorption on coagulation sludge pretreated by high-temperature

采用高温焙烧改性混凝污泥,通过SEM、XRD对改性前后的污泥进行了表征。本研究探讨改性污泥对水溶液中氨氮的吸附动力学、吸附热力学和吸附特性。结果表明：改性污泥对氨氮吸附符合Freundlich 吸附等温式;分别采用拟一级反应、拟二级反应和颗粒内扩散反应模型对吸附动力学过程进行了拟合,实验数据遵循拟二级动力学反应模型;并计算吸附热力学参数,在30、40和50℃下,对应的Gibbs自由能（ΔG0）分別为-1.915、-1.744和-1.719 kJ ·mol-1,显示该反应属自发性进行;焓变（ΔH0）〈0,证实该反应为放热反应;熵变（ΔS0）〈0,说明该吸附反应是熵值减小的过程;黏附概率S＊=0.0812介于0～1范围内,表明该吸附过程主要为物理吸附。

The characteristic of coagulation sludge was altered by the pretreatment of high temperature. The appearance and crystallization of coagulation were respectively characterized by SEM and XRD and the samples with pretreatment and without pretreatment were compared.The adsorption characteristic of pretreated sludge for adsorption of ammonia-nitrogen from the aqueous solution was also evaluated using the theory of thermodynamics and kinetics.The adsorption model of ammonia-nitrogen was fitted with the Freundlich equation.The kinetic equations of pseudo-first-order,pseudo-second-order and intra-particle diffusion were adopted to examine the mechanism of the adsorption process and the pseudo-second-order models provided the better correlation of adsorption data.Thermodynamic parameters including ΔG0,ΔH0,ΔS0,Ea, and S＊ were calculated.The values of ΔG0 at 30,40 and 50℃ were-1.915,-1.744 and-1.719 kJ·mol-1 respectively,indicating the spontaneous nature was happened in ammonia adsorption on altered coagulation sludge.The negative value of ΔH0 proved the existence of the exothermic nature in the modified sludge absorption process.The negative value of ΔS0 represented that the adsorption was a declining process for entropy.The S＊ value at 0.0812 ranged from 0 to 1 demonstrated that the adsorption was a physical process.