Immobilization of Heavy Metal Cations in Contaminated Mining Soils by High Temperature Activated Phosphate Tailings
Heavy metal contamination of soil at mining and metallurgical sites is an important environmental issue.Thus,there is an urgent need to develop cost effective remediation technologies.To date,chemical immobilization is one of the most commonly used techniques.However,most immobilization materials still suffer from low efficiencies and high costs.Here,activated phosphorus tailing materials treated at 900 ℃ were utilized to investigate their potential to support heavy metal immobilization in soils.The results showed that high temperature treatment decomposed dolomite in phosphate tailing to calcite,MgO and CaO.With the addition of activated phosphate tailing can elevate soil pH and decrease the concentrations of exchangeable heavy metals in soils.Amending 0.8％of activa-ted phosphate tailings for 30 day reduced the concentrations of exchangeable Zn,Cd and Pb in soils by 97％,46％and 95％,respec-tively.Furthermore,the amendment of activated phosphate tailings caused a redistribution of heavy metals in soil fractions.The ex-changeable heavy metals could be transferred into carbonate-associated fraction,and part of Cd was partitioned into Fe-Mn oxides bound fraction.The primary mechanism of immobilization was that the hydration of MgO substantially elevated soil pH,consequently leading to precipitation of heavy metal(hydr)oxides,and at the same time,increased adsorption of Cd to Fe-Mn oxides.The results of this study delivered a potential guideline for in situ soil remediation and reuse of phosphate tailings.
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