Enhancement effects of distiller's dried grains as reducing agents on the kinetics and leaching of pyrolusite from manganese ore

To solve the problem of environmental pollution, Distiller's dried grains (DDGS), a biomass, is used as a clean reducing agent for the leaching process of pyrolusite. Experimental results have shown that the leaching rate of manganese can reach 92.1% with the optimized conditions including a sulfuric acid concentration of 3.5 mol/L, a DDGS to pyrolusite ratio of 0.4, a liquid–solid ratio of 3 mL/g, a temperature of 363K, a time of 3 h, and a rotation speed of 400 rpm. This article explored the mechanism of the entire leaching process: the crude fiber in DDGS is hydrolyzed into reducing sugars, and the MnO₂ in pyrolusite undergoes an oxidation–reduction reaction to generate Mn²⁺ and studied the kinetics of the leaching process following the unreacted shrinkage nuclear reaction model controlled by the surface chemical reaction (1-(1-X)^1/3 = kt). The equation of leaching kinetics is [formula presented]^0.25·[rpm]^0.09·exp(−48.448/(RT)) This work provides a green and effective leaching process for the leaching of pyrolusite.