Kinetic study of the leaching of manganese mine tailings by organic reductant in sulphuric acid solution

A kinetic study of the leaching of manganese mining residue by sulphuric acid and potassium oxalate has been investigated. The effects of the agitation speed, manganese ore particle size, acid concentration, oxalate concentration and temperature on the manganese dissolution rate was determined. The leaching rate is significantly influenced by the reaction temperature, and both concentrations oxalate and acid. The observed effects of the relevant operating variables on the leaching rates are consistent with a kinetic model for chemical control. The apparent activation energy for the leaching of pyrolusite has been calculated using the Arrhenius expression and was found to be (63.7 +/- 2.9) kJ mol(-1). The experimental results indicate a reaction order of 1.07 for [H2SO4] concentration and 0.96 for [K2C2O4]. It is concluded that the reductive leaching of pyrolusite with potassium oxalate in acid medium is controlled by chemical reaction. The rate expression associated with the dissolution rate of pyrolusite depending on the parameters chosen may be summarised as follows: 1 - (1 - x)(1/3) = 1.4510(7)/r(0)(0.82).[H2SO4](1.07)[K2C2O4](0.96) exp(-63735/RT).t