Abstract:Leaching kinetics of pyrolusite was investigated with walnut shell as reductant in sulfuric acid solution. Effects of stirring rate, leaching temperature, concentration of sulfuric acid solution, and dosage of walnut shell on leaching rate of Mn were discussed. The results show that leaching rate of Mn rises with increase of stirring rate, leaching temperature, concentration of sulfuric acid solution, and dosage of walnut shell. Leaching rate of Mn rises rapidly in the first 60 min. Leaching rate of Mn is 93.18% under the conditions including leaching temperature of 369 K, concentration of sulfuric acid solution of 3.5 mol/L, dosage of walnut shell of 40 g/L, leaching time of 2.5 h, and stirring speed of 200 r/min. The leaching process is controlled by interfacial chemical reaction with apparent activation energy of 45.5 kJ/mol. Apparent reaction order of concentration of sulfuric acid and dosage of walnut shell is 0.897 and 0.2 respectively.