Sponsored by: LMD Reactive Metals Committee
Co-sponsored by: Canadian Institute of Mining, Metallurgy & Petroleum, Montreal, Canada; The Japan Institute of Metals, Sendai, Japan; Mining & Materials Processing Institute of Japan, Tokyo, Japan; Society for Mining, Metallurgy & Exploration, Littleton, CO
Program Organizers: B. Mishra, Department of Metallurgical & Materials, Engineering, Colorado School of Mines, Golden, CO 80401; G.J. Kipouros, Department of Mining & Metallurgical Engineering, Technical University of Nova Scotia, Halifax, Nova Scotia, Canada B3J 2X4; R.G. Reddy, Department of Chemical & Metallurgical Engineering, University of Nevada, Reno, NV 89557
Co-Organizers: W.A. Averill, Rocky Flats, Inc., Golden. R.G. Bautista, University of Nevada - Reno, Reno; M.C. Bronson, Lawrence Livermore Natl. Lab., Livermore; J.A. Sommers, Teledyne Wah Chang Albany, Albany; C.B. Wilson, The Dow Chemical Company, Freeport
Wednesday, AM Room: B9
February 7, 1996 Location: Anaheim Convention Center
Session Chairperson: Dr. R.G. Baustista, University of Nevada - Reno, Department of Chemical & Metallurgical Engineering, Mackay School of Mines, Reno, NV 89557; Dr. K. Liddell, Department of Chemical Engineering, Washington State University, Pullman, WA 99164
PROCESSING OF LOW GRADE ZINNWALDITE (LITHIUM MICA) CONCENTRATE: P. Alex, A.K. Suri, Metallurgy Division, Bhabha Atomic Research Center, Trombay, Bombay 400 085, India
Zinnwaldite, lithium bearing mica, is obtained as one of the byproduct during the beneficiation of wolframite ore of Degana (Rajasthan). It contains about 0.29 to 0.60% lithium, and some amounts of rubidium and cesium. Initially various processing schemes involving a combination of pyro- and hydro techniques were examined. This paper is concerned with the studies carried out on sulfuric acid leaching and pugging for a lithium concentrate analyzing 0.59% lithium. It was observed that acid leaching resulted in recovery of about 95% of lithium but the leach liquor contained a high proportion of iron. Recoveries in the acid pugging on the other hand were almost the same as in leaching but the iron contamination of the leach liquor was substantially low (Li to iron ratio of about 8:1). Lithium from the leach liquor was recovered as lithium carbonate by adopting a combination of ion exchange purification and chemical precipitation.
ROLE OF ION EXCHANGE REACTIONS IN THE IN SITU LEACHING OF URANINITE BY NH4HCO3 -(NH4)2CO3 -H2O2: J. Brantner, K. Liddell, Department of Chemical Engineering, Washington State University, Pullman, WA 99164
Ion exchange on clay mineral surfaces can alter the concentrations of solution species, the solubility of other minerals that share a common cation, and the porosity and permeability of the host formation. Equilibrium cation exchange reactions involving NH4+, Na+, K+, H+, Ca2+, and Mg2+ were incorporated in a mathematical model for in-situ leaching of UO2 by solutions of NH4HCO3, (NH4)2CO3, and H2O2. The clay surface was assumed to be in equilibrium with groundwater initially; contact with leach solution resulted in displacement of the Na+, K+, H+, Ca2+, and Mg2+ cations from the clay, often accompanied by precipitation of calcite and magnesite. Development of the ion exchange model is described and implications for successful in-situ uranium recovery and groundwater restoration are discussed.
REMOVAL OF RADIONUCLIDES USING ZEOLITES: R.G. Reddy, Z. Cai, Department of Chemical and Metallurgical Engineering, MS 170, University of Nevada, Reno, NV 89557
Adsorption of uranium (VI) from aqueous solutions on natural zeolites,i.e. chabazite, clinoptilolite, erionite and mordenite was investigated. The influence of time and pH of the solution were studied. The results showed that uranium (VI) species are strongly adsorbed on the zeolites between pH 6 to 9. The amount of uranium adsorption is strongly dependent on pH and to some extent, on the type of zeolites. For pH> 6 and at 25deg.C, more than 92% of uranium from solution was removed in 10 minutes. Adsorption mechansim of uranium and application of the results to some industrial systems are discussed.
10:00 am BREAK
NITRIDING PROCESS FOR THE RECOVERY OF VANADIUM FROM FERROVANADIUM: K. Singh, A.K. Suri, C.K. Gupta, Metallurgy Division, Bhabha Atomic Research Center, Trombay, Bombay 400 085, India
A three step process based on nitriding-leaching-pyrovacuum decomposition has been developed to prepare vanadium-nitrogen alloy from ferrovanadium. Recent investigations in our laboratory have vanadium-nitrogen alloy analyzing about 5.76%N and 0.28%C. Adopting this process a few hundred grams of V-N alloy has been prepared for use as soluble anode in fused salt electrorefining cell to prepare vanadium metal.
DISTILLATION MODELING FOR A URANIUM REFINING PROCESS: B.R. Westphal, Argonne National Laboratory, P.O. Box 2528, Idaho Falls, ID 83403
A part of the spent fuel treatment program at Argonne National Laboratory, a vacuum distillation process is being employed for the recovery of uranium following an electrorefining process. Distillation of a salt electrolyte, containing a eutectic mixture of lithium and potassium chlorides, from uranium is achieved by a simple batch operation and is termed "cathode processing". The incremental distillation of electrolyte salt will be modeled by both an equilibrium expression and on a molecular basis since the operation is conducted under moderate vacuum conditions. As processing continues, the two models will be compared and analyzed for correlation with actual operating results. Possible factors that may contribute to aberrations from the models include impurities at the vapor-liquid boundary, distillate reflux, anomalous pressure gradients, and mass transport phenomena at the evaporating surface. Ultimately, the purpose of either process model will be to enable the parametric optimization of the process.
A STUDY OF THE THERMAL DECOMPOSITION OF BaCO3 AND SrCO3: I. Arvanitidis, D. Sichen and S. Seetharaman: Theoretical Metallurgy, Royal Institute of Technology, S-100 44 Stockholm, Sweden
In the present work, the following decomposition reaction were studied: BaCO3(s) = BaO(s) + CO2(g) and SrCO3(s) = SrO(s) + CO2(g).
The rate of the thermal decomposition of the carbonates was followed by
thermogravimetric analysis (TGA) and differential thermal analysis (DTA)
simultaneously during heating in argon. Shallow powder beds and high argon
flows were employed. The DTA curves show a single phase transformation for
SrCO3 from rhombohedral to hexagonal form occurring at 1204 K. In the case of
BaCO3, two phase transformations could be observed, viz. from orthorhombic to
hexagonal at 1079 K and hexagonal to cubic at 1237 K. The mechanisms of the
reactions are examined in the light of the kinetic studies. In the case of
BaCO3 decomposition, BaCO3 forms an eutectic melt with the BaO, which is formed
as the product. The formation of the melt appears to play an important role in
the reaction kinetics. The activation energies for the decomposition of SrCO3
and BaCO3 were evaluated to be 290 and 305 kJ/mol., respectively. The results
are discussed in the light of the thermodynamic stabilities of alkaline earth
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