The Research On Chemical Remediation Of Lead Tailing During The Process Of Mineral Separation

With the increasing pollution of solid waste mine, tailings rehabilitation has been on the agenda. It has become the main source of heavy metal contamination in the mining areas, which including soil substrates contaminated, soil texture destroyed, short of nutrient, ecological landscape destroyed, water pollution and biological diversity decrease. Work should do to restore the ecology on mined areas. Basing on the research ago, choosing soil samples from Shikoushan lead-zinc mine, we investigated the application of soil washing technology in tailing soils.In the first study, using 0.05 mol·L-1 of EDTA as an extractant for Shuikoushan tailings in the tailings column, it carried out to explore the different extraction time on extraction efficiency, and the last column at different depths of extraction efficiency and time. The results indicated that, Pb, Cu, Zn and Cd 4 kinds of metal extraction efficiency with the increase of extraction time. Extraction after 60h, Pb, Cu, Zn and Cd extraction efficiency is 34.35%,49.45%,53.87%,56.14%. Extraction process, when the non-heavy metal contaminants into the soil element extractant solution, the extraction solvent and soil units occurring in the solid phase extraction system, the role of solid-phase transformation occurs gradually and heavy metal pollutants into the soil units of liquid systems extraction process is a dynamic equilibrium process, under certain conditions, heavy metals in the solid-phase system/liquid system, the output reached the maximum concentration of heavy metal pollutants. As the solid-phase system/liquid system, system balance takes time, so the concentration of heavy metals enter the soil unit is a first Cr increased gradually, gradually slow down after reaching the maximum process. It is for reasons the middle layer has peaks and gradually moving down. For the underlying tailings, compared with the middle layer of the tailings, its agents access to more adequate and extraction, the extraction process more fully, and the heavy metals extracted directly out of the system, making reverse occurred in the extraction process more difficult, so the heavy metal content than the maximum value is lower than the middle layer.In the second study, the redistributions of Pb, Zn and Cu were determined using the sequential extraction procedure of the optimized European Community Burean of Reference (BCR) before and after extraction. The results indicated that EDTA is a good chemical extraction agent, Percentage extractabilities of metal followed the sequence of Cd> Zn> Cu> Pb. In shallow soil, EDTA acid extractable metals extraction is particularly significant, but with the increase of soil column depth, acid extractable most easily re-adsorption. In deep soils, oxides bound, organic bound and residual forms of state 3 kinds of metal extraction efficiency decrease may be related to the decreased concentration of EDTA. With the increase of extraction time, extraction fluid volume also increased in the case, the heavy metal concentrations showed a significant reduction of all forms trend may be due to inhibition of re-adsorption. After extraction of all time, with the last increase in the depth of column, the various forms of metal concentration were increased, especially in the shorter extraction time, increase the concentration of the more obvious, there are three main reasons for this:①With the depth of the tailings increase, EDTA has the upper tailings as heavy metals play a role, to make the lower reaches of the EDTA concentration in the tailings decreased with decrease of extraction efficiency, which mainly after the extraction of deep soil oxides, organic combination state and residual state were higher than metal concentrations in shallow soil, low concentration of EDTA is not conducive to stability in the extraction of these three forms of metal;②tailings particles re-absorption, as the depth increases, the tiny tailings easy to adsorption chelating ion state and Me-EDTA, mainly manifested in the acid extractable heavy metal concentrations were significantly increased with increasing concentration;③As the permeability of the tailings is not a good role in water, so that extraction of slow, heavy metals were extracted sufficient time to re-adsorption by the end. However, extraction time, increase the amount of liquid case, the heavy metal extraction efficiency is improved.