A novel leaching process with highly-low residual organics from pyrolusite ore and its kinetics

This study focused on the exploration of a novel reductive leaching method from pyrolusite ore which can effectively reduce residual organics in leaching solution. Formaldehyde was used as a reductant to extract manganese from low-grade pyrolusite. Organic residue in the leaching solution was analyzed via HPLC. Kinetics model was also exposed. The optimized leaching conditions were as follows: H2SO4 concentration 2.21 mol/L, liquid-to-solid ratio 8:1, 2.5 ml formaldehydel/10g low-grade pyrolusite, stirring rate 200 r/min, leaching temperature 353 K and leaching time 120 min. The extraction ratios of Mn, Al, Fe, Mg, and Ca were 90.24%, 22.78%, 61.61%, 53.38%, and 84.2%, receptively under the optimized conditions. Formic acid was the main residual organic from the oxidized production of formaldehyde; its concentration was only 2.24 g/L. The kinetic data for leaching process obeyed a mix-controlled kinetic model. The apparent activation energy of leaching reaction was 34.81 kJ/mol for 0-30min, 30.1 kJ/mol for 30-150min, respectively.