Dissolution kinetics of hemimorphite in trichloroacetic acid solutions

In this study, the dissolution kinetics of hemimorphite in the presence of the organic reagent, trichloroacetic acid (TCAA), was investigated. Experimental variables such as reaction temperature (293-323 K), TCAA concentration (0.084-0.184 mol/dm(3)), particle size (0.081-0.214 mm), and stirring speed (200-650 rpm) were studied to determine the influence on the zinc dissolution rate, and a kinetic model was developed to represent the relationship. The results demonstrated that during the leaching process, zinc was rapidly dissolved in TCAA and the zinc leaching rate increased as a function of increased reaction temperature, TCAA concentration, and stirring speed, and decreased particle size. Among the kinetic models of the porous solids tested, a new variant of the shrinking-core model well described the zinc leaching kinetics. The activation energy was determined to be 54.94 kJ/mol, and the rate of reaction equation [1 - (2/3)x - (1- x)(2/3)](2) = [11.24(C)(3.80946)(PS)(-2.00833) (ss)(1.62147) exp(-54.94/RT)]t was also obtained to describe the process. (C) 2018 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda.