Preparation of strontium carbonate from celestite

Abstract

A novel method for the preparation of strontium carbonate from celestite ore has been investigated. The ore is reduced by brown coal at a temperature of 1000°C for a period of 3 h. The reduced product is leached with water at a liquid: solid ratio of 3: 1 at 90°C and the slurry is then leached with hydrochloric acid at a solid: liquid ratio of 2: 1. By controlling the pH at 1.5-2 and adding 20% H₂O₂ at the rate of 0.5 dm³/m³ of solution the oxidation process HS-→S^o is accomplished. Barium is precipitated with dilute sulphuric acid; and more than 90% Ca²⁺ + Mg²⁺ (and Fe) is removed when the pH is increased to 12. Addition of 1.2 times the theoretically required amount of NH₄HCO₃ at a solution strength of 2 mol/l at 60°C and at pH in the range 9-11 results in the precipitation of SrCO₃. The precipitate is washed and dried at 220-250°C. The proposed flowsheet is simple, has low consumption of acid and alkaline reagents, gives a high recovery of strontium and accepts a wide range of raw material.