Thermodynamic Modeling of the Na 2 O-SiO 2 -As 2 O 5 System and Its Application to Arsenic Immobilization Using Glass Fo
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https://doi.org/10.1007/s11837-020-04246-w 2020 The Minerals, Metals & Materials Society
THERMODYNAMIC MODELING OF SUSTAINABLE NON-FERROUS METALS PRODUCTION
Thermodynamic Modeling of the Na2O-SiO2-As2O5 System and Its Application to Arsenic Immobilization Using Glass Formation JUN-HYUNG LEE,1 SUN YONG KWON,1 PIERRE HUDON,1 and IN-HO JUNG 2,3 1.—Department of Mining and Materials Engineering, McGill University, Montreal, QC H3A 0C5, Canada. 2.—Department of Materials Science and Engineering and Research Institute of Advanced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea. 3.—e-mail: [email protected]
A critical evaluation and optimization of the Na2O-SiO2-As2O5 system was conducted using the CALPHAD method to obtain a consistent set of Gibbs energy functions for all solid, liquid and gas phases within the system. The available and reliable thermodynamic and phase diagram data of the unary As2O5 system and binary Na2O-As2O5 system were all well reproduced in the present optimization. The phase diagram of the SiO2-As2O5 system was predicted from the SiO2-P2O5 system based on the similarity between As2O5 and P2O5. The phase diagram and thermodynamic properties of the ternary Na2OSiO2-As2O5 system were predicted using the optimization results of the three binary systems. The strong short-range ordering behavior of the liquid Na2OSiO2-As2O5 solution was well described with the modified quasichemical model. The phase diagram, arsenic evaporation behavior and energy balance were calculated for the glass-making process related to arsenic immobilization from the present thermodynamic database.
INTRODUCTION Arsenic is a highly toxic element that often contaminates drinking water. Long-term exposure to inorganic arsenic through drinking contaminated water can lead to skin lesions and skin cancer.1 Concentrated inorganic arsenic can be produced by industrial processes such as mining and smelting of cobalt and gold as by-products. Yellowknife, in the Northwest Territories (Canada), is the location of the Giant Mine, one of the biggest environmental problems in Canada. A large amount of gold was mined there from 1948 to 2004. Unfortunately, large amounts of arsenic (over 237,000 tons in the form of arsenic oxide) were found in the ore with gold, and the arsenic tailings, produced after the processing of gold, were simply left in chambers and stopes at the mine site. Temporary solutions were applied but a permanent solution is still necessary.2
Currently, the copper industry is gaining increasing access to mineral deposits containing arsenic because of the depletion of copper ores. The same is true for the gold industry where ore bodies containing significant levels of arsenic are now under consideration. Consequently, in the pyro- and hydrometallurgical processing of such minerals, arsenic is becoming a major environmental problem that must be resolved for sustainable processing. One possible industrial route to minimize the environmental impact of arsenic is the stabilizat
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