Recovery of elemental sulfur during the oxidative ammoniacal leaching of chalcopyrite
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Effect of Temperature on Lithium Recovery after Roasting for Two Hours
Temperature. K
Recoveries,Pct
823 973 1173 1273 1373 1423 1473
43 50 64 69 78 88 69
52 51 64 68 80 89 71
49 55 59 68 76 85
47 54 52 65 75 86
AverageValue
49 50 58 67 77 --
48 52 60 68 78 87 70
Element
Table I demonstrates the dependence of the quantity of lithium extracted from spodumene upon the reaction temperature. The data show the calculated average of five runs at each indicated temperature where the deviation was about -+5.0 pct. The recovery is plotted as a function of temperature in Figure 1. It is evident that maximum recovery, about 87 pct, is achieved at 1423 K. Lower recoveries above this temperature are due to the fusion of silicates forming a protective layer of glassy substance. Also, it could be partly due to LiC1 volatilization. When tachyhydrite is heated it loses its water of crystallization, which amounts to 51.18 pct of its mass. Above 700 K it loses another 13 pct of its mass due to the transformation of MgCI2 into MgO. The total mass loss expected when tachyhydrite is heated to the reaction temperature is therefore 64.18 pct. Experimentally, when a mixture of 10.3 g tachyhydrite was reacted with 1 g spodumene at 1423 K, the mass of the sinter was found to be 4.87 g. Table II shows a comparison between expected theoretical values of some constituents and the corresponding values obtained by chemical analysis. It is to be noted that as the reaction temperature was increased, more losses in CI-, Li +, and Ca ++ were observed which might suggest some chloride volatilization. 1. Tachyhydrite can be used to open the spodumene structure for subsequent lithium recovery. This is essentially an alternative method of the classical chlorination method and achieves similar recoveries. 2. Maximum recoveries were obtained at 1423 K roasting for 2 hours with mixtures 8:1 by weight tachyhydrite: spodumene, and subsequent leaching in boiling water for 4 hours. % 95
85
E
75
65 ca 55
J 45
800
900
1000
1100
1200
1300
1400
1SO
TK
Fig. 1 --Recovery of lithium as a function of roasting temperature (roasting time 2 h). 726--VOLUME 15B, DECEMBER 1984
Table I1. Comparison between Theoretical Masses and Experimental Values Found through Chemical Analysis of the Leach Liquor of the Sinter Obtained from 10.3 g Tachyhydrite plus 1.0 g Spodumene
CI~ LiCa-Mg- Na- + K+ insoluble residue Total (mass of sinter)
Theoretical Mass. g 1.7291 0.0375 0.9774 0.5929
4.689
Mass Found after Reaction at 1423 K
Mass Found after Reaction at 1473 K
1.33 0.032 0.78 0.12 0.4
1.17 0.024 0.70
1.86 4.87
4.81
REFERENCES I. A.N. Zolikman, O. E. Krein, and G. V. Samsov: Metallurgy of Rare Metals, 2nd ed., Israel Program Scientific Translations, Jerusalem, 1966. p. 435. 2. Khalil Afgouni and J. H Silva: Lithmm Ore in Brazil, Arqueana de Minerios e Metais Ltda. Rua Maria Figueiredo. 374, Paraiso, 044002S. Paulo, 1978, pp. 1-13. 3. Anuario Mineral Brasileiro, published by the National Department of Mineral Production, The Ministry of Mines and
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