The effects of aluminum content, temperature and impurities on the electrical conductivity of synthetic bayer liquors
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EXPERIMENTAL Preparation of Solutions Pure sodium aluminate solutions were prepared by dissolving electrical grade AI wire in analytical grade NaOH solution. The dissolution reaction is highly exothermic and was conducted in covered polypropylene beakers, cooled and diluted to 1 liter. Impurities were added to the prepared pure solutions as analytical reagent grade sodium carbonate and sodium oxalate and technical grade sodium succinate. The prepared solutions were stable with respect to alumina trihydrate precipitation indefinitely in the absence of seed material.
This concept is not new2-9 but published data describing its quantitative application to solutions of industrial composition are inherently limited in range due to the requirement to maintain operating conditions and generally serve as deviation indicators under conditions of constant temperature and total soda content. Laboratory application of this technique is demonstrated in the literature by the authors ~~and Kelly I~ over a limited range of temperature, total soda and alumina contents. The aim of this investigation was to extended the range of electrical conductivity data to cover solution conditions commonly found during the precipitation stage of the Bayer process and to investigate the effects of some significant impurities on conductivity.
Bayer liquors are described in terms of their free soda content (expressed as Na20) alumina content (expressed as A1203) and total soda content (expressed as Na20). The difference between total soda and free soda is a measure of impurity content (mainly Na2CO3). In this study, the range of solution compositions and temperature used maintained consistency with published data 1-8 describing the precipitation stage of the Bayer Process.
G. R. BROWNE, formerly Post-Graduate Student, School of Mining and Mineral Technology, Kalgoorlie, Western Australia, is presently Metallurgist, Kambalda Nickel Operations, Western Mining Corporation. C. W. P. FINN, formerly Alcoa Foundation Lecturer in Thermodynamics, School of Mining and Mineral Technology, Kalgoorlie, Western Australia, is presently Associate Professor of Pyrometallurgy, University of the Witwatersrand, Johannesburg, Republic of South Africa. Manuscript submitted February 21, 1980.
The conductivity of the solutions was measured using a Philips PW 9501/01 Conductivity Bridge in earthed mode with an external reference resistance of 1.000~2 (_+ 0.01). The conductivity cell was a Philips PR 9514/10 immersion probe with a cell constant of 1.00 cm-l (_+ 0.01) at a measuring frequency 200 Hz. Conductivity bridge output was monitored on a Metrohm Labograph chart recorder.
Composition and Temperature Range
Conductivity Measurements
ISSN 0360-2141/81/0911-0487500.75/0 METALLURGICAL TRANSACTIONS B 9 1981 AMERICAN SOCIETY FOR METALS AND VOLUME 12B, SEPTEMBER 1981--487 THE METALLURGICAL SOCIETY OF AIME
Table I. Range of Variables Used in Conductivity Measurements
Variable Free soda Alumina Sodium carbonate Sodium oxalate Sodium succinate Total soda Temperature
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