粉煤灰中微量有害元素的淋滤特性研究

Study on leaching characteristics of trace harmful elements in fly ash

为探究粉煤灰中微量有害元素的淋滤特性,采用淋滤实验研究了粗、细两种粒径粉煤灰中As、Hg、Cr、Cd和Pb的淋滤特性。实验结果表明,粉煤灰中Cd、Cr、Pb在酸性条件下随着实验时间的增加,淋出速度逐渐放缓,且在前96 h几乎完全淋出;As在前48 h完全淋出;Hg不受酸性条件的影响,实验全程无淋出;细颗粒粉煤灰中As、Cr、Cd和Pb的淋出量始终大于粗颗粒粉煤灰。将实验结果与GB/T 20426—2006《煤炭工业污染物排放标准》中煤炭工业废水有毒污染物日排放量限值要求进行对比,发现淋滤0—24 h后粗、细颗粒粉煤灰滤出液中As、Cr、Cd和Hg的含量均满足标准限值要求,但Pb的含量超标,表明在极苛刻的酸性条件下,粉煤灰中Pb的淋出量可能超标。

In order to explore the l eaching characteristics of trace harmful elements in fly ash,the leaching characteristics of As,Hg,Cr,Cd and Pb in the coarse and fine fly ash were studied through leaching experiment.The results showed that with the increase of the experiment time,the leaching rate of Cd,Cr,and Pb in fly ash was decreased gradually under acidic conditions,and they were almost leached completely in the first 96 h;As was leached completely in the first 48 h,Hg was not leached throughout the experiment,and it was not affected by acidic conditions.The contents of As,Cr,Cd and Pb in leachate in fine fly ash were always greater than those in coarse fly ash.By comparing the results of the leaching experiment with the limits requirements of the emission standard for coal industry pollutant,it was found that the contents of As,Cr,Cd and Hg in the fly ash leachate of coarse and fine particle size in 0—24 h all met daily emission limits requirements of toxic pollutants from coal industry wastewater as specified in GB/T 20426—2006 Emission Standard for Pollutants from Coal Industry.However,the Pb in the leachate exceeded the limit requirement.It showed that under extremely harsh acidic conditions,the amount of Pb leaching in fly ash may exceed the limit.