Chemical Engineering Journal 114 (2005) 67–72 Dissolution kinetics of sphalerite in acidic ferric chloride leaching S. Aydogan a,∗ , A. Aras a , M. Canbazoglu b a Department of Mining Engineering, Selcuk University, Konya, Turkey b Department of Mining Engineering, Cumhuriyet University, Sivas, Turkey Received 13 May 2005; received in revised form 5 September 2005; accepted 13 September 2005 Abstract This paper presents a study for leaching kinetics of sphalerite concentrate in FeCl 3 –HCl solution. The shrinking core model was applied to the results of experiments investigating the effects of stirrer speed of 200–600 rpm, ferric ion concentration in range of 0–1 M, solid/liquid ratio in range of 1/100–1/5, leaching temperature range of 40–80 ◦ C and particle size on zinc dissolution rate. The activation energy for the leaching process was found to be 45.30 kJ/mol and the Arrhenius constant was calculated to be 5.454 s -1 . The order of reaction for ferric ion concentration, solid/liquid ratio and particle size were also obtained. The rate of the reaction based on reaction-controlled process can be expressed as, [1 - (1 - α) 1/3 ] = k 0 (Fe 3+ ) 0.36 (ρ S/L ) -0.33 r -0.97 0 exp (-45300/RT ) t. The dissolution of sphalerite with acidic ferric chloride solution was found to be controlled by reaction-controlled process. © 2005 Elsevier B.V. All rights reserved. Keywords: Sphalerite; Ferric chloride; Leaching; Kinetic model; Reaction-controlled process 1. Introduction Sphalerite (ZnS), which associates mainly with other metal sulphide minerals, such as chalcopyrite (CuFeS 2 ), galena (PbS) and pyrite (FeS 2 ) in the nature, is the principal source from which zinc is produced commercially. In mineral processing engineering, they are collected in separate concentrates through selective conventional froth flotation applied to separate each other. Sphalerite concentrates usually contain more than 50% Zn. Conventional zinc recovery process from sphalerite con- centrates involves roasting the concentrate to zinc oxide or sulphate, leaching the resultant calcine with dilute sulphuric acid and electrodepositing of zinc from purified leach solu- tion (roasting–leaching–electrowinning, RLE) [1]. The need to utilize small and complex deposits and the environmental restric- tions imposed on sulphide smelters stimulated the development of alternative methods, especially hydrometallurgical routes that avoid the production of SO 2 as a pollutant. The elimination of roasting step is an important advan- tage and high zinc extraction increases the importance of ∗ Corresponding author. Tel.: +90 332 2232060; fax: +90 332 2410635. E-mail address: saydogan@selcuk.edu.tr (S. Aydogan). hydrometallurgical treatment processes. For this purpose, vari- ous leaching studies have been performed by many researchers in basic medium using ammonia solution [2–7] or in acidic medium using nitric acid [8], hydrochloric acid [9–11], sul- phuric acid [12,13] and also oxidating agents, such as ferric ions [14–20]. Ferric ion, which is one of the most important oxidative agents in leaching process, is mostly used from the source of ferric chloride (FeCl 3 ) and ferric sulphate (Fe 2 (SO 4 ) 3 ). Fer- ric chloride is well recognized as a leaching agent and it was reported that ferric chloride has more advantage than ferric sulphate [14,15]. Many investigations indicate that sphalerite can be dissolved readily under certain conditions. Neverthe- less, few kinetic studies for the sphalerite dissolution have been reported. Sphalerite leaching with acidic ferric chloride solutions products, including zinc chloride and other zinc chloride complexes, elemental sulphur, ferrous chloride, Fe 2+ and Fe 3+ complexes and sulphides (H 2 S, HS - ,S 2- ), mainly depending on the solution pH. The dissolution reaction of sphalerite in acidic ferric chloride solutions, which was a simple oxidation–reduction reaction, was expressed as follows [21]: ZnS + 2Fe 3+ → Zn 2+ + 2Fe 2+ + S 0 (1) 1385-8947/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2005.09.005