Mwase, James
Safarian, Jafar
2021-06-30
<p>The study is currently evaluating the hydrometallurgical aspects of the Pedersen process as an alternative<br>
route to the Bayer process for producing metallurgical grade alumina. The Pedersen process is<br>
potentially applicable on lower grade ores and a wider variety of bauxite materials. The test material<br>
used was slag which was obtained through the smelter-reduction of a mixture of bauxite residue (red<br>
mud) and a calcite-rich bauxite beneficiation by-product. The process was evaluated at lab-scale using<br>
a 1 L jacketed glass reactor.<br>
Six experimental programmes were conducted each consisting of a leaching, desilication and precipitation<br>
test. Samples of the slag were leached with Na2CO3 solution at 90 °C. The tests varied in<br>
Na2CO3 concentration and leaching time. Additionally, different approaches to leaching involving<br>
mechanical treatment of the leached slag and re-leaching using either fresh or recycled solution were<br>
also explored. The desilication step was carried out by treating the leachate solution with powdered<br>
CaO at 70°C varying the amounts used. Finally, the desilicated solution was sparged with a gas mixture<br>
of equal parts Ar and CO2 after which the precipitate was allowed to age in the solution for a<br>
period of time. The carbonation and aging temperatures and times were varied. As much as 73 % of<br>
the Al has been leached from the slag. The desilication process has shown to remove 88 % of the Si.<br>
The precipitation process produced a product composed entirely of the aluminium tri-hydroxides. It<br>
was observed that the unwanted phase of dawsonite in the final product can perhaps be avoided by<br>
using a solution of Na2CO3 with concentrations not more than 60 g/l. Furthermore, the carbonation<br>
and aging temperatures should not exceed 30 °C.</p>
https://doi.org/10.5281/zenodo.5012308
oai:zenodo.org:5012308
Zenodo
https://zenodo.org/communities/eu
https://doi.org/10.5281/zenodo.5012307
info:eu-repo/semantics/openAccess
Creative Commons Attribution 4.0 International
https://creativecommons.org/licenses/by/4.0/legalcode
EMC2021, European Metallurgical Conference 2021, 27-30 June 2021
Aluminium tri-hydroxides, bauxite materials, Pedersen process
Production of Aluminium Tri-hydroxides from Secondary Bauxite Materials
info:eu-repo/semantics/conferencePaper