Mineralogy, geochemistry and release of heavy metals in wastes from indigenous zinc smelting in Northwest Guizhou

Environmental impact resulting from mining activities is serious and ubiquitous all over the world, and it has become one of the important aspects in environmental geochemistry. The environment was seriously damaged by wastes from historical zinc smelting in Northwest Guizhou. The geochemical distributions of Pb and Zn in the different grain-size fractions of wastes indicate that the coarser particles show similar or even higher heavy metal concentrations than finer ones in the samples, although the concentrations of heavy metals tend generally to increase as the size fractions get finer. The heavy metal contents are very high, with maximum values of 31631, 57178, 2367 and 311.5 mg/kg for Pb, Zn, Cu and Cd, respectively. It is also shown that the residual fraction of Pb is less than that of Zn, accounting for 0.39%-15.75% and 14.3%-46.2%, respectively, of the total, and this is likely relative to Zn-silicate minerals formed from smelting. Although the relative partitioning of Pb and Zn is very low （0.03%- 1.3.% for Pb; 0.03% -3.3% for Zn）, the exchangeable fraction of the waste contains large amounts of heavy metals （1.5%-385 μg/g for Pb; 3-590 μg/g for Zn）. Heavy metals in exchangeable forms have the highest solubility to give the highest potential bioavailability in contrast to other chemical forms. Mineralogical study indicates that the wastes were found to be highly heterogeneous materials, dominated by quartz, feldspar, carbonatite, iron or/and aluminum vitric compounds and a few secondary mineral phases, and their contents vary with the type of smelting wastes. The secondary minerals formed from smelting and sequentially weathering are the major chemical phase for heavy metals. Complex composition of many phases and substitution of elements suggested that many of the phases were found to be non-stoichiometric compounds. Pb was found to be the main Pb phase in the wastes by precipitation or/and adsorption.     

深海锰结核以煤代焦还原熔炼新工艺研究

针对锰结核焦炭还原熔炼成本高、焦炭生产过程环境污染严重等问题,作者提出了锰结核以煤代焦还原熔炼新工艺,对减少锰结核冶炼环境污染、降低冶炼成本,具有积极意义.以东北太平洋中部深海锰结核为原料,对还原温度、还原时间、硅石加入量、无烟煤加入量对锰结核中Co、Ni、Cu、Fe、Mn回收率的影响进行了研究.结果表明:500 g锰...