Investigation of alumina production from pumice by hydrometalurgical methods

In this thesis study, the possibilities of alumina production from pumice were investigated by evaluating the acidic pumice obtained from Kayseri region by hydrometallurgical methods. It was aimed to produce alumina by leaching from the pumice with 64.64% SiO2 and 14.85% Al2O3 content. For this purpose, pumice was leached in water, HCl, H2SO4 and HNO3 solutions and the aluminium recoveries in these media were revealed. As a result of the leaching of the run-of-mine pumice in all media, a significant amount of aluminium could not be taken into the solution, so it was milled at various times between 2-60 minutes using a planetary ball mill in order to mechanically activate the pumice. The milled products were leached under constant conditions and the highest aluminium recovery (66.40%) was obtained as a result of leaching the intensively 60 min. milled pumice with HCl solution. As a result of studies investigating the effect of temperature, time and acid concentration parameters to increase aluminium recovery, it was increased to 91.37% by leaching in 4 M HCl solution at the boiling temperature for 24 hours. AlCl3 salt precipitated from this leach solution through evaporation was roasted at 1200 °C for 3 hours and pumice alumina was produced for the first time. It was observed that alumina has 62.87% Al2O3 content, while sodium and potassium contents were very low, iron and calcium contents were high. As a result, a basic flow sheet including mechanical activation, acid leaching, solution purification, precipitation and roasting stages was proposed for alumina production from pumice.