粉煤灰砖块对磷酸盐的吸附特性

以建筑废料粉煤灰砖块为吸附剂材料,通过静态吸附实验研究其对磷酸盐的吸附特征,以及磷酸盐初始浓度、吸附剂投加量、pH等因素对吸附反应的影响。Langmuir、Freundlich和Temkin等温模型的分析发现,Langmuir等温式方程最适合描述吸附过程,对磷酸盐的理论饱和吸附容量为44.62 mg/g。利用伪一级动力学模型、伪二级动力学模型和颗粒内扩散模型考察了吸附过程特征,其中伪二级动力学模型为最适于描述粉煤灰砖块对磷酸盐的吸附过程的动力学模型。通过颗粒内扩散模型、Bangham方程及Boyd模型对吸附动力学机理进行的探讨表明,颗粒内扩散速率不是粉煤灰砖块吸附磷酸盐反应的惟一速率控制步,膜扩散速率和颗粒内扩散速率共同影响着吸附反应速率。磷酸盐浓度较低时主要是膜扩散限制吸附反应速率,而磷酸盐浓度较高时则颗粒内扩散成为速率控制步。研究证明,粉煤灰砖块粉末作为湿地基质具有对磷酸盐很强的吸附能力,在减少了固体废弃物的数量的同时又可以实现水污染控制的目的。

Adsorptive characteristics of fly ash blocks to phosphate

The adsorption characteristics of fly ash blocks powder to phosphate were evaluated. Batch adsorption were conducted to study the effects of various parameters such as initial concentration, adsorbent dosage and solution pH on phosphate adsorption. Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data, and the Langmuir isotherm fitted the experimental data significantly better. The phosphorous theoretical saturated adsorption capacity was 44.62 mg/g. Adsorption kinetics data were also tested using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. It showed that the adsorption process followed a pseudo-second-order reaction. The mechanism of the adsorption process was determined from the intraparticle diffusion model, external diffusion model, Bangham's equation and Boyd model. The mechanism studies revealed that the process was complex and followed both surface adsorption and particle diffusion. It was found to be controlled by the film diffusion at lower concentrations, and at higher concentration, the particle diffusion becomes the rate-determining step. The outcome indicated that fly ash blocks powder was a promising material for the removal of phosphate in constructed wetlands, which provided a win-win approach for both the construction solid waste disposal and wastewater control.