Sethurajan Manivannan, Huguenot David, Lens Piet N L, Horn Heinrich A, Figueiredo Luiz H A, van Hullebusch Eric D
Laboratoire Géomatériaux et Environnement (LGE), Université Paris-Est, EA 4508, UPEM, 77454, Marne-la-Vallée, France.
Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX, Delft, The Netherlands.
Environ Sci Pollut Res Int. 2016 Apr;23(8):7504-16. doi: 10.1007/s11356-015-6014-1. Epub 2016 Jan 4.
Various mineral processing operations to produce pure metals from mineral ores generate sludges, residues, and other unwanted by-products/wastes. As a general practice, these wastes are either stored in a reservoir or disposed in the surrounding of mining/smelting areas, which might cause adverse environmental impacts. Therefore, it is important to understand the various characteristics like heavy metal leaching features and potential toxicity of these metallurgical wastes. In this study, zinc plant leach residues (ZLRs) were collected from a currently operating Zn metallurgical industry located in Minas Gerais (Brazil) and investigated for their potential toxicity, fractionation, and leachability. Three different ZLR samples (ZLR1, ZLR2, and ZLR3) were collected, based on their age of production and deposition. They mainly consisted of Fe (6-11.5 %), Zn (2.5 to 5.0 %), and Pb (1.5 to 2.5 %) and minor concentrations of Al, Cd, Cu, and Mn, depending on the sample age. Toxicity Characteristic Leaching Procedure (TCLP) results revealed that these wastes are hazardous for the environment. Accelerated Community Bureau of Reference (BCR) sequential extraction clearly showed that potentially toxic heavy metals such as Cd, Cu, Pb, and Zn can be released into the environment in high quantities under mild acidic conditions. The results of the liquid-solid partitioning as a function of pH showed that pH plays an important role in the leachability of metals from these residues. At low pH (pH 2.5), high concentrations of metals can be leached: 67, 25, and 7 % of Zn can be leached from leach residues ZLR1, ZLR2, and ZLR3, respectively. The release of metals decreased with increasing pH. Geochemical modeling of the pH-dependent leaching was also performed to determine which geochemical process controls the leachability/solubility of the heavy metals. This study showed that the studied ZLRs contain significant concentrations of non-residual extractable fractions of Zn and can be seen as a potential secondary resource for Zn.
通过各种选矿作业从矿石中生产纯金属会产生污泥、残渣及其他不需要的副产品/废物。通常，这些废物要么存储在蓄水池中，要么处置在采矿/冶炼区域周边，这可能会对环境造成不利影响。因此，了解这些冶金废物的各种特性，如重金属浸出特性和潜在毒性非常重要。在本研究中，从位于巴西米纳斯吉拉斯州一家目前运营的锌冶金厂收集了锌厂浸出残渣（ZLRs），并对其潜在毒性、分级和浸出性进行了研究。根据生产和沉积年限，收集了三个不同的ZLR样品（ZLR1、ZLR2和ZLR3）。它们主要含有铁（6 - 11.5%）、锌（2.5%至5.0%）和铅（1.5%至2.5%），以及少量的铝、镉、铜和锰，具体含量取决于样品年限。毒性特性浸出程序（TCLP）结果表明，这些废物对环境有害。加速社区参考局（BCR）连续萃取清楚地表明，在温和酸性条件下，镉、铜、铅和锌等潜在有毒重金属会大量释放到环境中。液固分配随pH值变化的结果表明，pH值在这些残渣中金属的浸出性方面起着重要作用。在低pH值（pH 2.5）时，可浸出高浓度的金属：分别可从浸出残渣ZLR1、ZLR2和ZLR3中浸出67%、25%和7%的锌。金属的释放量随pH值升高而降低。还进行了pH值依赖性浸出的地球化学模拟，以确定哪种地球化学过程控制重金属的浸出性/溶解性。本研究表明，所研究的ZLRs含有大量非残留可萃取锌组分，可被视为锌的潜在二次资源。
