Kinetic model for direct leaching of zinc sulfide concentrates at high slurry and solute concentration

Direct Acid Leaching of Sphalerite: An Approach Comparative and Kinetics Analysis

“…However, at sufficiently high pulp density, diffusion of reactants appears to be limited given the increasing concentration of products of the reaction. With respect to the oxidation of sphalerite, several authors reported the overall chemical reaction of the leaching process [10][11][12][13][14][15][16][17][18][19] Some authors [20] reported that leaching of sphalerite occurred mainly according to Equation (2). Other researchers [18] reported that the sphalerite dissolution rate in acid media was controlled by oxygen diffusion through a porous surface layer of polysulfide or S 0 .…”

“…With respect to the oxidation of sphalerite, several authors reported the overall chemical reaction of the leaching process [10][11][12][13][14][15][16][17][18][19] as follows (Gibbs energy values were obtained from HSC Chemistry 6 [29]:…”

“…However, comparing the energies values between Equations ( 7) and (8), its shows that the oxidation reaction is more thermodynamically possible in the presence of sulphuric acid rather than just H + . According to previous equations, ferric iron reacts with ZnS and is reduced to ferrous ion, which the oxidizes to ferric ion when it reacts with oxygen present in the leaching system; these reaction favor oxidant conditions during leaching [11]. The thermodynamics seems to indicate that the formation of zinc sulfate (aqueous) is more favored than the zinc ion.…”

“…Although the conventional method for the recovery of zinc has been used over several years, direct leaching of sphalerite concentrates has recently aroused great interest [9][10][11][12][13][14][15][16][17][18][19]. The direct leaching process omits the roasting stage; in this process, elemental sulfur is produced instead of sulfur dioxide, and effective zinc extraction can be achieved independently of the iron concentration in the zinc concentrates [5].…”

“…In general, direct leaching processes can be carried out in pressure leaching autoclaves or in agitated tanks operating at atmospheric pressure [20,21]. Atmospheric direct leaching is less expensive than the direct pressure leaching process due to lower maintenance costs [11]. Thereby, there is an increased interest in the use of atmospheric pressure leaching [22].…”