Ceramics-Silikáty 53, (2) 108 - 112 (2009)

A zinnwaldite concentrate with 1.40% Li processed in this study was prepared from zinnwaldite wastes (0.21% Li) using dry magnetic and grain size separations. Zinnwaldite wastes originated from dressing Sn–W ores, which were mined in the past in the Czech Republic in Cínovec area. The extraction process of lithium, so-called gypsum method consisted of sintering the concentrate with CaSO₄ and Ca(OH)₂, subsequent leaching of the sinters obtained in H₂O, solution purification and precipitation of Li₂CO₃. It was observed that almost 96% lithium extraction was achieved if sinters prepared at 950°C were leached at 90°C, liquid-to-solid ratio = 10:1, reaction time of 10 min. The weight ratio of the concentrate to CaSO₄ to Ca(OH)₂ was 6 : 4.2 : 2. Lithium carbonate product containing almost 99% Li₂CO₃ was separated from the condensed leach liquor, from which calcium was removed by carbonate precipitation.