Rare Earth Ore Flotation Principles and Kinetics: Significance of Collectors and Application of Novel Depressants

The lanthanides are more commonly referred to as rare earth elements (REEs). Approximately 250 rare earth minerals (REMs) are known but vary in their composition as solid solutions. Because REEs have similar properties, REMs are usually separated from invaluable gangue into a single bulk concentrate. Flotation is almost universally the method of choice. Flotation is a complex process that works based on differences in hydrophobicity, involving a plethora of variables that enhance those differences with the goal of improving the grade and recovery of the REMs reporting to the concentrate. In this regard, flotation is briefly reviewed from reagent, machine, and flowsheet design perspectives with application to REMs. It is stressed that REM flotation depends on REE coordination number and cation size, typically requiring the need for collector blends. A case study is then presented to illustrate the importance of depressants. This was accomplished by examining their role on the first-order rate constant in kinetic modeling. Four novel depressants were identified and a parametric design of experiments was conducted. The study looked at the type of depressant and the dosage of collector to generate a statistically significant model using a three-compartmental kinetic approach. Not only were grade and recovery examined but so was the response of the first-order rate constant to changing experimental conditions.