Akademik Veri Yönetim Sistemi
HYDROMETALLURGY, cilt.61, sa.3, ss.185-194, 2001 (SCI-Expanded)
The effects of HCl concentration and temperature on the dissolution of La2O3 in aqueous (HCl-H2O), mixed-aqueous (HCl-CH3OH-H2O) and non-aqueous (HCl-CH3OH) solvents have been studied. Increase of methanol in solvents was determined to cause corresponding decreases in conductivity, E-SCE, pH values with corresponding increase in ER values and better results were obtained for dissolution in the order non-aqueous > mixed-aqueous > aqueous solvent systems. Increase in dissolution was attributed to the prevention of lanthanum hydroxide precipitation in non-aqueous medium. Lanthanum compounds formed in non-aqueous medium at 25 degreesC were isolated and identified using X-ray diffraction, thermal and chemical analysis methods and the thermal changes observed in these compounds between 25 degreesC and 1100 degreesC were investigated. LaCl3 . x(1)CH(3)OH and LaCl3 . x(2)CH(3)OH . 3H(2)O (x(1) + x(2) = 2.35) were formed in non-aqueous medium and these compounds were converted into LaCl3 . 1.14CH(3)OH with complete and partial loss of water and methanol around 165 degreesC, respectively. Methanol was completely removed around 200 degreesC with formation of LaCl3 and some LaOCl and due to the decomposition of LaCl3 above 200 degreesC, LaOCl was detected as the only stable phase above 700 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.