Synthesis of barium carbonate by mechanochemical method

In this research, barium carbonate was synthesized via mechanochemical method from the mixture of barite concentrate-sodium carbonate. The producing of barium carbonate form barite concentrate and the evaluation of the phases/products were the goal of this research.

After crushing the barite concentrate, the acid washing process was done with 1 N of HCl. The mixtures of barite concentrate-sodium carbonate with different molar ratios (BaSO4:Na2CO3=1:1, 1:2, 1:2.5) were prepared and milled in a planetary mill for different times (2 and 5 hours). The as-milled samples and the heated products were dissolved in distilled water and then the solid residues were dried in an oven. The isothermal heating of the samples was done into the alumina and zirconia crucibles. The unmilled mixture of barite concentrate-sodium carbonate was also prepared. The findings of this research were evaluated using XRF, XRD and STA methods and the microstructures of the samples were studied by SEM method.

The2 and 5 h-milled mixtures showed the sign of chemical reaction between the starting materials (barite concentrate-sodium carbonate) at 720⁰C in STA results. This sign however was observed at 735 ͦC in the unmilled mixture. According to XRD patterns, the chemical reaction between barite concentrates and sodium carbonate was not completed in the milled mixtures. The signs of orthorhombic phase of barium carbonate were observed in the products after isothermal heating at700⁰C for 1 h. The results indicated that the isothermal heating of the milled mixture of barite concentrate-sodium carbonate with a molar ratio of 1:2.5 at 750⁰C for 2 h was the suitable conditions for synthesizing of barium carbonate. Additionally, the weak signs of an intermediate phase (Ca4Ba2Si6O18) were observed in the XRD patterns of the barite concentrate-sodium carbonate mixture. For comparison, the experiments were performed with pure barium sulfate sample (Barex). In the product of isothermal heating (750⁰C, 2 h) for the mixture of barium sulfate (Barex)-sodium carbonate (molar ratio :1:2.5), barium carbonate phase was produced and no trace of the intermediate phase was observed. The results of this research showed that it is possible to synthesis barium carbonate phase from the mixture of barite concentrate-sodium carbonate using ball milling process and isothermal heating.