响应曲面分析优化改性粉煤灰漂珠对水中氟的吸附性能及机理研究

为提升粉煤灰漂珠对水溶液中氟的吸附性能，以氧化钙为原料，采用煅烧法制备钙改性粉煤灰漂珠吸附材料.通过响应曲面分析中的Box-Behnken设计吸附氟试验，探讨各吸附因数及其交互作用对吸附效果的影响，确定最佳吸附条件.利用SEM（扫描电镜）、EDS（能量散射光谱）、XRD（X射线衍射）以及BET比表面积等手段对吸附材料进行表征，并结合吸附动力学、吸附等温试验探讨钙改性粉煤灰漂珠吸附剂的除氟机制.结果表明:①初始ρ（F-）和吸附温度对改性粉煤灰漂珠吸附水中F-的去除率有显著影响，当pH为5.0、初始ρ（F-）为125 mg/L、吸附温度为40℃时，改性粉煤灰漂珠对水中F-的吸附效果最佳.②动力学试验显示，改性粉煤灰漂珠对水中F-的吸附过程符合准二级动力学模型，说明该吸附过程主要以化学吸附为主；与Langmuir和Freundlich吸附等温模型相比，Temkin吸附等温模型更适合于描述该吸附平衡过程.③SEM、EDS和BET比表面积分析显示，改性后的粉煤灰漂珠内部生成了具有不规则表面和多孔结构的含钙团簇物质，从而增加了BET比表面积，改善了孔隙结构.XRD分析显示，钙改性粉煤灰漂珠主要通过离子交换作用吸附去除水中的F-.研究显示，以工业废物为原料制备的钙改性粉煤灰漂珠吸附剂的最大除氟率为93.59%，是一种具有应用潜力的低成本吸附材料. 

Optimization Study of Adsorption Parameters for Removal of Fluoride by Fly Ash Cenospheres Modified with Calcium Using Response Surface Methodology

In order to improve the adsorption efficiency of adsorbent for removal of fluoride in wastewater, the fly ash cenospheres modified with calcium were prepared by annealing method. Through the Box-Behnken response surface methodology design of adsorption fluorine experiments, the effects of adsorption factors and their interactions were investigated, and the optimal adsorption conditions were determined. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and specific surface area analysis (BET) were employed to characterize the physicochemical properties of the adsorbents. The mechanisms of fluoride adsorption were investigated by means of adsorption kinetics and isothermal adsorption experiments. The results suggested that:(1) The initial F- concentration and adsorption temperature significantly affected the removal efficiency of F-; the optimal adsorption conditions were at pH of 5.0, initial F- concentration of 125 mg/L and adsorption temperature of 40℃. (2) The experimental kinetic data were well fitted by the pseudo-second-order model, which indicated that the dominant adsorption belonged to the chemisorption. The Temkin isotherm model was more suitable for describing the adsorption equilibrium than the Freundlich or Langmuir isotherm model. (3) The SEM, EDS and BET analyses indicated that Ca-containing cluster materials with irregular surface and porous structure were formed inside the fly ash cenospheres, which led to increases in porosity and specific surface area. The XRD analysis showed that the removal of F- from water by the fly ash cenospheres was mainly via the ion-exchange. These results showed that the maximum F- adsorption rate of the fly ash cenospheres modified with calcium and prepared from industrial waste is 93.59%, and the low-cost adsorption material has potential application.