Refining of crude Li2CO3 via slurry phase dissolution using CO2

Refining of crude Li2CO3 produced from salt lake brines of Qinghai, China, by direct carbonation with CO2-water solutions under different conditions was studied. The process is based on the reaction of Li2CO3 with CO2-water solutions to convert the former to the more soluble lithium bicarbonate. The carbonation experiments were carried out in a three-phase mechanically agitated slurry-bed reactor. The parameters that may affect the dissolution of Li2CO3 in CO2-water solution such as CO2 pressure, temperature, CO2 flow rate, solid concentration, particle size of Li2CO3, slurry filling degree, agitator shape and agitation speed were investigated. The effects of immersion time of Li2CO3 in the slurry before carbonation as well as multiple carbonation cycles were also examined. It was found that the rate of dissolution of Li2CO3 increased with increasing CO2 pressure inside the reactor, agitation speed or CO2 flow rate. Furthermore, it increased with decreasing Li2CO3 particle size, slurry filling degree, reaction temperature or solid concentration. The immersion time had almost no effect on the carbonation ratio of Li2CO3. By multiple carbonations, it was possible to convert all of the insoluble Li2CO3 to lithium bicarbonate. The kinetics of the carbonation process in determined time intervals can be properly represented by 1 - (1 - X)(1/3) = kt. Finally, the Arrhenius activation energy of the carbonation reaction was obtained by calculation. (C) 2007 Elsevier B.V. All rights reserved.