摘要
利用XRD、TEM/EDS和连续提取实验研究了土法炼锌固体废渣中重金属的矿物学特征及不同粒度中重金属的相态分布特征。与通常发现的重金属一般富集在小粒径废渣中的情况不同,本工作所研究的废渣样品中大粒径废渣与细粒径废渣相似,甚至有更高的金属含量。化学形态研究表明,冶炼过程形成的矿物(或玻璃质)集合体和堆积后的风化过程形成的次生矿物是废渣中重金属存在的主要化学相。同时发现Pb的残渣态很少(0.39%～15.75%),而Zn的残渣态较高(14.3%～46.2%),这可能与冶炼工艺所形成较多Zn的硅酸盐矿物有关。尽管可交换态Pb、Zn在不同相态中的相对比例非常小(Pb0.03%～1.30%;Zn0.03%～3.30%),但其绝对含量却比一般土壤或沉积物要高(Pb1.5～385μg/g;Zn3～590μg/g)。由于重金属可交换态有比其他化学相态更高的活动性和生物可利用性,因此,对环境有较大的潜在影响。废渣样品的微束分析表明,Pb在废渣中见有金属Pb存在形式或呈纳米金属Pb颗粒包裹于其他矿物或铁合金及熔球集合体中。同时不排除有Pb的碳酸盐矿物存在的可能。而以硅锌矿Zn2(SiO4)、锰硅锌矿(Zn,Mn)2犤SiO4犦和纤维状的丝锌铝石Zn8Al4犤(OH)8(SiO4)5犦·7H2O等矿物形式存在以及Fe、Mn等的铝硅酸盐形式存在的Zn,可能是导致Zn的残渣态较高的原因。与连续提?
The geochemical distributions of Pb and Zn in the different grain size fractions have been investigated chemically by sequential extraction analysis and mineralogically by X ray diffraction (XRD) and analytical transmission electron microscope with EDS (TEM/EDS). In general, concentrations of heavy metals tend to increase as the size fractions get finer. However, the coarser particles show similar or even higher heavy metal concentrations than finer ones in the study samples. Study on chemical fractionation shows that secondary minerals formed from smelting and sequentially weathering are the major chemical phase for heavy metals. It is also showed that the residual fraction of Pb is less than that of Zn, constituting 0.39% ～ 15.75% and 14.3% ～ 46.2% , respectively, of total concentration. This is likely relative to Zn silicate mineral formed from smelting. Although the relative partitioning of Pb and Zn is very low (0.03% ～ 1.30% for Pb; 0.03% ～ 3.30% for Zn), the exchangeable fraction of the slages contains large amounts of heavy metals (1.5～ 385 μ g/g for Pb; 3～ 590 μ g/g for Zn). Heavy metals in exchangeable forms have the highest solubility to give the highest potential bioavailability in contrast to the other chemical forms. The mineralogical study indicates that complex composition of many phases and substitution of elements meant that many of the phases are found to be non stoichiometric compounds. Metal Pb is found to be mainly Pb phases in the slags by precipitation or/and adsorption. The mineral compositions of Zn are more complex than that of Pb. Zn bearing minerals include willemite, tephrowillemite, zinalsite, and occasionally metal Zn can be found in the slages. This is possible reason that the relative partitioning of Zn in residue fraction is higher than that of Pb. It is in a good agreement with the result of chemical study.<P>
出处
《地球化学》
CAS
CSCD
北大核心
2003年第2期139-145,共7页
Geochimica
基金
中国科学院知识创新工程项目(KZCX2-105)
