the Effect of Mechanical Activation on the Synthesis of Strontium Carbonate via Black-Ash Process

Abstract

Celestite is the main raw material for producing strontium carbonate, which is widely used in color TV tubes, electroceramics, pyrotechnics, and zinc refining. The black-ash method is an economical route for this production, involving three steps: reducing celestite to strontium sulfide (SrS), dissolving SrS in hot water, and precipitating SrCO₃ from the solution. Although this process yields high-purity product, it consumes significant energy. In this study, mechanical activation was applied to reduce energy consumption by lowering the reduction temperature, improving dissolution, and shortening reaction time. Graphite was used as the reductant and sodium carbonate as the precipitant. TGA-DTA analysis determined the optimal milling time and reduction temperature. Celestite powder (76% purity) mixed with graphite was mechanically activated in a planetary mill, then heated at 900°C for one hour to convert SrSO₄ to SrS. The SrS was leached in 90°C water for one hour to separate gangue, and SrCO₃ was precipitated by adding sodium carbonate. The final product had 76.4% purity with over 99% recovery. Acid washing of the celestite increased product purity to 97.8%, showing that raw material purification greatly affects final quality.