Soil Washing and Bioremediation of Slime Dam Material
The solvent extraction section of an old Uranium Plant in the Vaal River region produced a substance called Crud (Chalk River Unidentified Deposit) that formed within the aqueous/organic interface of the settler of the solvent extraction circuit.The crud was deposited together with gold tailings to the tailings dam many years ago.Previous research done on the crud confirmed that exposed crud leaches Mn and Ni at concentrations that are well above their acceptable risk limits as well as Zn that leaches at concentrations that are slightly lower than its acceptable risk limit.Soil washing and bioremediation technologies were employed to treat the contaminated soil.Various laboratory test work and the pilot scale studies were conducted in parallel with each other and the results of the laboratory studies were used to determine critical parameters.Four lixiviants,i.e.sulphuric acid,acetic acid,oxalic acid and ethylene diamine acetic acid were tested at three concentration levels i.e.0.001M,0.0001M and 0.00001M,respectively.Column tests showed that the leaching of the heavy metals increases as the soil porosity increases.Silica sand was added to increase porosity of the contaminated soil.Highest Mn removal was achieved mainly by sulphuric and oxalic acid at 0.001M at all soil levels.EDTA was significantly efficient in the removal of Ni and Zn.The recovery of heavy metals,particularly Mn,decreased as the depth of sampling increased. Heterogeneous bacteria and filamentous organism plate counts were conducted to evaluate the growth of the bacteria and filamentous organisms in the soil.Results showed that more organism growth took place in the bioremediated soil with a fertilizer added to it.The leaching of metals from the soil that was bioremediated in the pilot study was generally higher than the extraction of the metals from the soil that was leached with no bioremediation carried out.The results from this study suggest that the leaching of heavy metals from the contaminated soil is to a large extent dependant on the pH of the leaching solution.By increasing the soils porosity and bioremediating the soil,higher extractions of metals were achieved.
Slime dam material Bioremediation technologies Soil washing
T.Shumba L.Lorenzen
Department of Process Engineering,University of Stellenbosch,Matieland,South Africa
国际会议
XXIV International Mineral Processing Congress(第24届国际矿物加工大会)
北京
英文
4082-4089
2008-09-24（万方平台首次上网日期，不代表论文的发表时间）