超细粉煤灰吸附亚甲基蓝的机理研究

以西安西郊热电厂粉煤灰(XFA),西安灞桥热电厂粉煤灰(BFA)和陕西渭河电厂粉煤灰(WFA)为原料,球磨后经旋风分级再用布袋收集逸出物分别得到超细粉煤灰XUFA、BUFA和WUFA。研究了超细粉煤灰对亚甲基蓝的吸附动力学、热力学以及pH值对吸附的影响。结果表明,超细粉煤灰对亚甲基蓝的吸附性能明显好于原粉煤灰。超细粉煤灰对亚甲基蓝的吸附性能按顺序为WUFA>XUFA>BUFA。粉煤灰颗粒粒度、比表面积和活性组分(SiO2 Al2O3)含量是影响粉煤灰吸附性能的主要因素。WUFA对亚甲基蓝的吸附符合Langmuir吸附等温式,而XUFA和BUFA对亚甲基蓝的吸附符合Freundlich吸附等温式。超细粉煤灰对亚甲基蓝的吸附均符合二级吸附动力学模型,吸附过程由颗粒内扩散过程控制。当溶液pH由2增加到8时,超细粉煤灰吸附量增加,后随pH值增加,吸附量略有下降。

STUDY ON THE ADSORPTION MECHANISM OF ULTRA-FINE COAL FLY ASH TOWARDS METHYLENE BLUE

Three kinds of coal fly ashes were collected from Xi'an West Suburb Thermal Power Plant (XFA), Xi'an Ba-Qiao Thermal Power Plant (BFA) and Shannxi Weiriver Thermal Power Plant (WFA), respectively. Raw coal fly ashes were ball milled and separated by cyclone separator, those particles gathered by bag filter were the ultra-fine coal fly ashes named XUFA, BUFA and WUFA. Mechanism and effect of pH of the adsorption of methylene blue onto ultra-fine coal fly ashes were studied. The results showed that the adsorption capacities of methylene blue on ultra-fine coal fly ashes were much higher than that of raw coal fly ashes. For ultra-fine coal fly ashes, the adsorption capacities decreased in the order of WUFA>XUFA> BUFA. Particle size, specific surface area, and active component (SiO2 Al2O3) content were the main factors as for the adsorption capacity. The adsorption isotherm of methylene blue on WUFA could be described by the Langmuir model, while those on XUFA and BUFA fit the Freundlich equation well. The adsorption kinetics of methylene blue onto three ultra-fine coal fly ashes followed the second-order kinetic equation, and the adsorption processes were controlled by the intra-particle diffusion. The adsorption amount onto ultra-fine coal fly ashes increased with the initial pH-value of the solution in the range of 2~8, whereas decreased slightly with the pH-value above 8.