摘要
以某废弃铜冶炼厂收集的铜冶炼烟尘作为样本,采用TCLP毒性浸出和宽溶液pH(3～13)范围浸出实验,研究了铜冶炼烟尘中重金属的释放行为及其矿物学控制机制.结果表明,TCLP浸出液中As、Cd、Cu、Pb和Zn浓度分别是我国《危险废物鉴别标准浸出毒性鉴别》(GB 5085.3-2007)中相应元素限值的704倍、82.7倍、2.08倍、3.1倍和3.26倍.在整个溶液pH处理范围内,As的释放率高达26.0%～28.1%.在酸性条件下Cd、Cu和Zn的浸出率明显较高,而Pb在pH 13.0时释放率较高.地球化学分析表明,在pH 5.5～11.5的溶液处理下,As的溶解度部分受新形成的Ca、Cu、Pb和Zn砷酸盐控制,而Cd、Cu、Pb和Zn的溶解度主要受碱性条件下氢氧化物沉淀形成控制.BCR顺序提取和XRD分析表明,浸出液中Cd和Zn浓度较高与其在灰尘中赋存活性态比例高一致.研究结果为烟尘处理或处置防止重金属污染提供科学指导.
Abstract
The release behavior of heavy metal(loid)s in Cu smelting flue dust,collected from a deserted Cu smelter,and its mineralogical control mechanism were studied using toxicity characteristic leaching procedure(TCLP)test and wide pH range(3-13)dependent leaching experiments.The concentrations of As,Cd,Cu,Pb and Zn in TCLP leachate were 704,82.7,2.08,3.1 and 3.26 times threshold of corresponding elements listed in identification standards for hazardous wastes of China(GB 5085.3-2007),respectively.High release percentage of As ranged from 26.0%to 28.1%over the entire pH range.The leachability of Cd,Cu,and Zn was significantly high under acidic conditions,while that of Pb was highly released at pH 13.0.The geochemical analysis showed that As solubility was partly controlled by the new formation of Ca,Cu,Pb,and Zn arsenates under pH 5.5-11.5,and that of Cd,Cu,Pb,and Zn was mainly controlled by hydroxide precipitation under alkaline condition.BCR extraction and XRD analysis indicated that higher leachate Cd and Zn concentrations were consistent with their higher content of active forms in dust.The study provides scientific guidance for the treatment and disposal of the flue dust for heavy metal(loid)s pollution prevention.
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