Investigation of Vietnamese monazite concentrate decomposition by alkaline (KOH) baking method

Abstract

The alkaline (NaOH) hydrometallurgy for monazite concentrate is currently being used in the industrial production of total rare earth oxides (TREOs) and thorium oxide (ThO2). Besides the acknowledged advantages, the hydrometallurgical process also has certain disadvantages such as the requirement for ultra-fine grinding to -325 mesh, and the hydrometallurgy time extended from 8 to 10 hours to achieve ~93 % efficiency. The present paper report a new roasting process using potassium hydroxide (KOH) applied to Vietnamese monazite concentrates. The experimental data were collected using mass analysis, XRD, and ICP-OES analysis. The optimal efficiency of the process is ~95% after roasting time of 0,5 hours, the temperature at 250oC, and KOH:monazite mass ratio = 1:1. Thereby, the alkaline (KOH) roasting process has solved the limitations of the alkaline (NaOH) hydrometallurgy and shows the development potential in deep processing of the monazite concentrate in Vietnam.