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

Laboratory experiments were carried our to assess the potential of forming ettringite in lime-remediated sulphidic mine tailings. The crucial paramete rs in optimizing and stabilizing the formation of ettringite in mine tailin gs are the availability of calcium aluminum sulphate and high pH environmen t. The optimization experiments revealed that for the railings sample under study, 5% lime is the threshold of the lime requirement to establish the r equired pH condition for the formation and precipitation of ettringite. Att aining and maintaining such a high pH is necessary for ettringite formation . The high metallic content of the tailings sample partially replaced the r equired trivalent aluminum from the ettringite structure and reduced the re quired stochiometric amounts of aluminum needed to form ettringite. The solubility of the admixtures (i.e. calcium and aluminum compounds) incr eases with the increase of the water content of the sample. However, the po tential of reusing the treated tailings constrains the water content of the mixtures. Therefore, the optimum wafer content of the sample was chosen ba sed on the workability characteristics of the mixture.