Ettringite formation in lime-remediated mine tailings: II. Experimental study

Laboratory experiments were carried out to assess the potential of forming ettringite in lime-remediated sulphidic mine tailings. The crucial parameters in optimizing and stabilizing the formation of ettringite in mine tailings are the availability of calcium, aluminum, sulphate and high pH environment. The optimization experiments revealed that for the tailings sample under study, 5% lime is the threshold of the lime requirement to establish the required pH condition for the formation and precipitation of ettringite. Attaining and maintaining such a high pH is necessary for ettringite formation. The high metallic content of the tailings sample partially replaced the required trivalent aluminum from the ettringite structure and reduced the required stochiometric amounts of aluminum needed to form ettringite. The solubility of the admixtures (i.e. calcium and aluminum compounds) increases with the increase of the water content of the sample. However, the potential of reusing the treated tailings constrains the water content of the mixtures. Therefore, the optimum water content of the sample was chosen based on the workability characteristics of the mixture.Laboratory experiments were carried out to assess the potential of forming ettringite in lime-remediated sulphidic mine tailings. The crucial parameters in optimizing and stabilizing the formation of ettringite in mine tailings are the availability of calcium, aluminum, sulphate and high pH environment. The optimization experiments revealed that for the tailings sample under study, 5% lime is the threshold of the time requirement to establish the required pH condition for the formation and precipitation of ettringite. Attaining and maintaining such a high pH is necessary for ettringite formation. The high metallic content of the tailings sample partially replaced the required trivalent aluminum from the ettringite structure and reduced the required stochiometric amounts of aluminum needed to form ettringite. The solubility of the admixtures (i.e. calcium and aluminum compounds) increases with the increase of the water content of the sample. However, the potential of reusing the treated tailings constrains the water content of the mixtures. Therefore, the optimum water content of the sample was chosen based on the workability characteristics of the mixture.