Scandium extraction from silicates by hydrometallurgical process at normal pressure and temperature

Abstract

Silicate is an important rock-forming mineral. In this work, a method called “sulfuric acid curing” was proposed, aiming to extract rare earth element scandium from silicates. Sulfuric acid curing refers to the addition of concentrated sulfuric acid to heated silicates at 60–300°C, and subsequently water leaching of the treated silicates at 30–75°C. The effects of sulfuric acid dosage, curing time, curing temperature, pulp density, leaching temperature and stirring speed on scandium leaching were investigated. Under the condition of sulfuric acid dosage with 0.75 times of the theoretical amount, curing time of 15 h, curing temperature of 200°C, pulp density for L/S ratios of 30:1, leaching temperature of 75°C, stirring speed of 100rpm, Sc(III) concentration of 492μg/L in the solution was achieved. XRD analysis shown that major phases of the samples hardly changed after acid curing. However, SEM-EDS examination of the samples demonstrated that morphology and particle size of minerals were changed obviously after being cured and leached. Leaching kinetics was further calculated, which can be described by the shrinking core model. The apparent activation energy for the dissolution was determined to be 55.49kJ.mol− 1.