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The dissolution kinetics of colemanite in phosphoric acid solutions was studied. The effects of particle size, temperature, acid concentration, solid-to-liquid ratio, and stirring speed on the dissolution rate were determined. It was observed that the dissolution rate increased with decreasing particle size and solid-to-liquid ratio and with increasing temperature, but stirring speed had no effect on it. The dissolution rate increased up to an acid concentration of 19.52% (by wt) and then decreased with increasing acid concentration. The dissolution kinetics of colemanite were examined according to the heterogeneous and homogeneous reaction models for the acid concentration range of 1.43−19.52% (by wt) of acid concentration, and it was found that the dissolution rate was controlled by surface chemical reaction. The activation energy of this process was determined to be 53.91 kJ mol-1.

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In this study, the leaching kinetics of malachite [CuCO 3 ‚Cu(OH) 2 ], an oxidized copper ore, was investigated in water saturated with ammonia gas. In the experiments, the ammonia concentration of the solution, the particle size of the ore, the temperature, the stirring speed, and the solid-to-liquid ratio were chosen as parameters. It was determined that the leaching rate of malachite increased with decreasing particle size and solid-to-liquid ratio and increasing reaction temperature, ammonia concentration, and stirring speed. The leaching kinetics was examined by statistical methods applied to the experimental data. It was found that the leaching rate fitted a pseudo-second-order kinetic model with an activation energy of 85.16 kJ‚mol -1 .