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    Dissolution kinetics of galena in acetic acid solutions with hydrogen peroxide
    (ELSEVIER SCIENCE BV, 2007) Aydogan, Salih; Aras, Ali; Ucar, Goekhan; Erdemoglu, Murat
    The kinetics of leaching lead from galena in acetic (ethanoic) acid solutions with hydrogen peroxide are investigated with regard to stirring speed, temperature and concentration of HAc and H(2)O(2) concentration. Oxidation of galena with H(2)O(2) to produce lead sulphate which dissolves by complexing Ph(2+) with acetate anion (PbCH(3)COO(+) and Pb(CH(3)COO)(2)). Results indicate that the rate of galena dissolution is controlled by a surface chemical reaction with an apparent activation energy is 65.6 kJ mol(-1)I in the temperature range 30-70 degrees C. Both HAc and H(2)O(2) affect the rate of extraction of lead as an acetate complex. The order of reaction was 0.79 and 0.31 for H(2)O(2) and HAc concentrations, respectively. (C) 2007 Elsevier B.V. All rights reserved.
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    Kinetics of galena dissolution in nitric acid solutions with hydrogen peroxide
    (ELSEVIER SCIENCE BV, 2007) Aydogan, Salih; Erdemoglu, Murat; Ucar, Goekhan; Aras, Ali
    The extraction of lead from a galena concentrate in nitric acid solutions with additional hydrogen peroxide was studied taking stirring speed, temperature, hydrogen peroxide and nitric acid concentrations, and particle size as dissolution parameters. The dissolution curves followed the surface chemical reaction controlled shrinking core model over the whole range of parameters, except at high nitric acid concentrations where the reaction was diffusion-control led. The activation energy of 42 KJ mol(-1) and a linear relationship between rate and inverse particle size support the reaction controlled dissolution mechanism. Hydrogen peroxide addition accelerated the reaction compared with nitric acid alone. It was concluded that the dissolution process is favourable, since the acid consumed for oxidation of galena can easily be regenerated in the same reactor by means of hydrogen peroxide. (c) 2007 Elsevier B.V. All rights reserved.
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    Kinetics of sphalerite dissolution by sodium chlorate in hydrochloric acid
    (ELSEVIER SCIENCE BV, 2009) Ucar, Goekhan
    The extraction of zinc from a sphalerite concentrate using sodium chlorate as an oxidant in hydrochloric acid solutions was examined. It was determined that stirring speed did not significantly affect zinc extraction compared with other experimental parameters. The dissolution rate increased with increasing sodium chlorate and hydrochloric acid concentrations and temperature, but decreased with increasing particle size. The kinetic Study showed that the dissolution of zinc could be represented by a shrinking core model with surface chemical reaction. The activation energy (Ea) for the dissolution reaction was calculated as 41.1 kJ/mol. (C) 2008 Elsevier B.V. All rights reserved.