改性粉煤灰净化酸性矿山废水污染机理研究

Research on the mechanism of modified fly ash treatment of acid mine drainage pollution

煤矸石堆存过程中产生的酸性矿山废水(acid mine drainage,AMD)对周边水环境具有严重污染风险。基于“以废治废”理念,选择煤炭燃烧产生的粉煤灰开展了去除AMD中污染物的研究。针对粉煤灰原灰处理效果不佳的现状,对比了不同改性条件下的粉煤灰对AMD中污染物的去除效果,筛选出了去除效果最佳的粉煤灰改性材料,并从微观层面解析了粉煤灰改性材料去除污染物过程中的作用机理。结果显示:经Ca(OH)_(2)助熔焙烧改性粉煤灰处理后,模拟AMD废水中的Fe、Mn含量由100mg/L降至低于1 mg/L,污染物去除率达99%。Ca(OH)_(2)助熔焙烧改性粉煤灰对Fe、Mn的吸附过程主要为单层化学吸附,在0~2 h内吸附接近平衡。此外,Ca(OH)_(2)助熔焙烧改性增加了粉煤灰表面粗糙度和孔隙数量,并在表面形成六面体晶相结构。同时,Ca(OH)_(2)助熔焙烧改性过程活化了粉煤灰颗粒表面Si和Al元素,提高了其Zeta电位,减少了游离羟基,增加了固定羟基,从而增强了其对污染物的吸附能力。Ca(OH)_(2)助熔焙烧改性显著提高了粉煤灰对AMD中污染物的去除率,为粉煤灰治理AMD提供了材料与方法依据。

Acid mine drainage(AMD)generated in the process of coal gangue storage poses a serious pollution risk to the surrounding water environment.Based on the concept of"waste to waste",fly ash from coal combustion was selected for the study of contaminant removal in AMD.In response to the poor treatment effect of fly ash(raw ash),we compared the removal effect of fly ash under different modification conditions on the pollutants in AMD,screened out the fly ash-modified materials with the best removal effect,and analyzed the mechanism of the fly ashmodified materials in the process of pollutant removal at the microscopic level.The results showed that the Fe and Mn contents in the simulated AMD wastewater were reduced from 100 mg/L to less than 1 mg/L with 99%pollutant removal after treatment by Ca(OH)_(2) flux roasting modified fly ash.The adsorption of Fe and Mn by Ca(OH)_(2) fluxroasted modified fly ash was mainly monolayer chemisorption,and the adsorption was close to the equilibrium in 0-2 h.In addition,Ca(OH)_(2) flux roasting modification increased fly ash surface roughness and pore number,and formed a hexahedral crystalline phase structure on the surface.Meanwhile,Ca(OH)_(2) flux roasting activated Si and Al elements on the surface of the fly ash particles,increased their Zeta potential,reduced the free hydroxyl groups,and increased the fixed hydroxyl groups,which enhanced their adsorption capacity.The Ca(OH)_(2) flux roasting modification significantly improved the removal efficiency of pollutants in AMD by fly ash,which provided a material and methodological basis for treating AMD by fly ash.