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 1 - 1 - X-1/3 = 3738.06 center dot [H2SO4](0.57) center dot [L/S](0.78 )center dot [ DDGS/pyrolusite](0.25 )center dot [rpm](0.09) center dot exp( -48.448 / (RT)) This work provides a green and effective leaching process for the leaching of pyrolusite. (C) 2022 The Author(s). Published by Elsevier B.V.