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STUDYING TEMPERATURE EFFECT ON SYSTEM EQUILIBRIUM STATES AT COBALT PRODUCTION WASTE ROASTING

https://doi.org/10.21285/1814-3520-2018-9-173-183

Abstract

The PURPOSE of the paper is to study the effect of temperature on the equilibrium states of the system under roasting of sludge/Na2CO3 charge. METHODS. The arsenic recovery rate and its yield are determined by arsenic content variation in the initial samples of charge and aqueous leaching cakes. The content of arsenic in dump and cake samples is determined by the x-ray fluorescent method. The phase composition of waste is studied on the XRD-6000 diffractometer. The equilibrium composition of systems is calculated in the computer program HSC Chemistry 6.0. RESULTS AND THEIR DISCUSSION. Having studied the variation rate of arsenic recovery from cobalt production waste under charge roasting within the temperature range of 600-900°C, it was shown that the rate of arsenic recovery (as a soluble product of Na3AsO4) is maximum at the temperature of 700-740°C. It has been found out that the temperature influences the equilibrium composition of the system where Na2CO3 reacts with ten low soluble arsenates Ca3(AsO4)2, AlAsO4, Mg3(AsО4)2, Ni3(AsО4)2, Сo3(AsО4)2, Fe3(AsО4)2, Pb3(AsО4)2, Zn3(AsО4)2, Сu3(AsО4)2, FeAsО4. The chemical equilibriums of reactions of all listed arsenates excluding iron (III) arsenate are shifted towards the Na3AsO4 yield in the researched conditions at the temperatures above 600°C. This is due to their endothermic thermal effects (ΔH>0). At the same time, as the temperature grows the depth of the equilibrium shifts weakens due to the decrease in their ΔH values. In the case of FeAsO4 and Na2CO3 interaction the equilibrium shift increases in the direction of the reverse reaction, i.e. consumption of Na3AsO4 due to the release of heat (exothermic reaction, ΔH<0) as the temperature grows. CONCLUSIONS. The phase composition of sludge in the waste dumps of recently not operating plant “Tuvacobalt” is represented by calcite, dolomite, quartz, silicates and low soluble arsenates. The latter are transformed into water-soluble Na3AsO4 in the process of sludge and soda charge (ratio 1:1) roasting. The rate of arsenic recovery in the form of sodium arsenate increases in the roasting temperature range of 600-740°C. The highest value of the arsenic recovery of 3.33 mg/min, and its maximum recovery degree of 85% (if its content in the charge decreases from ~ 4.0 to 0.7wt %) is detected at the temperatures of 700-740°C.

About the Authors

M. O. Moldurushku
Tuvinian Institute for Exploration of Natural Resources of Siberian Branch of Russian Academy of Sciences
Russian Federation


A. F. Chuldum
Tuvinian Institute for Exploration of Natural Resources of Siberian Branch of Russian Academy of Sciences
Russian Federation


L. Kh. Tas-Ool
Tuvinian Institute for Exploration of Natural Resources of Siberian Branch of Russian Academy of Sciences
Russian Federation


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Review

For citations:


Moldurushku M.O., Chuldum A.F., Tas-Ool L.Kh. STUDYING TEMPERATURE EFFECT ON SYSTEM EQUILIBRIUM STATES AT COBALT PRODUCTION WASTE ROASTING. Proceedings of Irkutsk State Technical University. 2018;22(9):173-183. (In Russ.) https://doi.org/10.21285/1814-3520-2018-9-173-183

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