Influence of ultrasound in ammoniacal leaching of a copper oxide ore
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K. SARVESWARA RAO, Scientist E-II, Hydro & Electrometallurgy Division, and K.L. NARAYANA, Scientist E-I, K.M. SWAMY, Scientist F, and J.S. MURTY, Scientist F and Head, D & P.E. Division, are with Regional Research Laboratory (CSIR), Bhubaneswar—751013, Orissa, India. Manuscript submitted October 4, 1996.
Table I.
copper oxide ore have been obtained using mechanical agitation as well as by a sonication technique. The raw material used was of Malanjkhand (Madhya Pradesh, India) origin. The oxide ore was crushed, ground, and sieved to obtain the required size fractions. The chemical composition and mineral phases identified are indicated in Table I. The lixiviants and wash solutions were prepared using reagent grade chemicals and distilled deionized water. The experiments were carried out in a cylindrical glass reactor of 100 mL capacity (70-mm height and 50-mm diameter, equipped with a mechanical glass stirrer with a turbine impeller of 25-mm diameter) kept in a water thermostat at atmospheric pressure. The experimental variables studied are given in Table II. Mechanical agitation was maintained constant at 200 rpm (191 rd z s21) throughout the experimentation. The leaching experiments under sonication were carried out with a 375 W ultrasound generator of 20 kHz frequency. The transducer used was of the piezoelectric type with a cup horn.[6] The leach slurry samples were collected at regular intervals, allowed to attain ambient temperature for obtaining uniformity in extraction of metal values, and then filtered. The leach liquor was analyzed for copper using a PERKIN-ELMER* atomic absorption spectrophotom*PERKIN-ELMER is a trademark of Perkin-Elmer Physical Electronics, Eden Prairie, MN.
eter (Model 372). A comparative study of copper recovery with mechanical agitation compared to sonication was made using varying pulp densities. The study was conducted at ambient temperature (298 K) using a fixed range of particle size (2300 1 150 mm) in 2M ammoniacal solution. The results of copper recovery are presented in Figure 1. Copper recovery was found to increase nonlinearly with time for either pulp density. Copper recovery improved with the decrease of pulp density. For a given specific time, ultrasound enhanced the recovery. This study also shows that the leaching time was reduced by nearly 6 times (from 120 to 20 minutes) to obtain the same copper recovery when using ultrasound. The effect of particle size was investigated using four size fractions at 298 K. These experiments were carried out by maintaining the ammonia concentration at 2M and solid/liquid ratio of 1/100 at a constant stirring speed. The results are shown in Figure 2 and indicate, as expected, that the leaching rate was affected by the particle size, being found to increase with a decrease in particle size. This can be attributed to the increase in the number of particles per unit weight of the solid, resulting in an increased unit surface area that results in greater exposure of ore particles to the lixiviant. The application of ultrasound for a spe
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