THERMODYNAMIC ANALYSIS WITH SOFTWARE: CASE STUDY OF UPGRADING RARE EARTH ELEMENTS CONTENT IN BANGKA TIN SLAG

The prospect of Bangka tin slag (BTS) as secondary rare earth element is found in some previous works. The separation process of BTS to gain precious metal oxides needs high reagent consumption and produces toxic wastes. Due to this, it is recommended to run simulation using database HSC chemistry software before conducting real experiment or real production. This paper reports simulation results of BTS roasting, BTS dissolution in hydrofluoric acid (HF), and BTS dissolution in hydrochloric acid (HCl) followed by BTS dissolution in sodium hydroxide (NaOH). The module used in this experiment is the reaction equation module, the thermochemical data diagram module, and the Eh-pH diagram module. From the simulation, it is known that Gibbs energy (DG) increases with increasing roasting temperature up to 900°C. The dissolution of major other oxides (MOOs) in HF shows that all the reactions are irreversible. However, the dissolution of major other oxides (MOOs) in HCl and then in NaOH shows that the reaction is irreversible only in CaO and Fe2O3. If the aim of the experiment is only to dissolve all dominant REE oxides, it is recommended to conduct dissolution in pH 0 to 1 with electrical voltage of 1-1.5 Volt.