Phase changes in mechanically activated spodumene-Na2SO4 mixtures after isothermal heating
School of Engineering
Mixtures of spodumene + Na2SO4 with a mass ratio of 1:0.5 were prepared and milled using either zirconia or metallic media in a planetary ball mill for 5 h. The milled samples were heated in a furnace at temperatures ranging from 800 °C to 1000 °C for one hour under an air atmosphere. X-ray diffraction (XRD) results showed the traces of new phases such as LiNaSO4 and β-spodumene in the produced calcine after isothermal roasting. Increasing temperature resulted in increasing formation of LiNaSO4 and the XRD results were consistent with a thermodynamic assessment of the spodumene-Na2SO4 mixture. The results showed that changing the milling media did not have a significant role in formation of phase(s) during isothermal heating regime. The XRD results revealed that LiNaSO4 was the major phase after heating a 5 h milled mixture of spodumene-Na2SO4 in both metallic and zirconia media at 1000 °C. There were signs of β-spodumene observed in the sample heated at 800 °C however the peaks of this phase were overlapped with LiNaSO4 phase. The dissolution of lithium during leaching in water reached ~92% for the 5 h milled samples after heating at 1000 °C irrespective of milling media used.