Study On The Wet Leaching Of Pyrolusite From Corn Distiller's Grains Enhanced By Microwav

Distiller’s dried grain with solubles（DDGS）are the residue left after fermentation and brewing,which can be hydrolyzed into reducing sugars in an acidic environment and have good reducing properties.In view of my country’s manganese resources,there are problems such as low occupancy rate,low grade,fine embedded particle size,and high impurity content.This paper proposes a microwave-enhanced process of corn distiller’s grains wet leaching pyrolusite.Microwave heating is used as a heat source,and Distiller’s dried grain with solubles is used as a reducing agent in the wet reduction process of manganese ore.The main research contents are as follows:（1）Through routine experiments,it was found that the factors affecting the leaching effect of manganese include sulfuric acid concentration,liquid-solid ratio,ratio of distiller’s grains to pyrolusite mass,temperature,time,stirring rate.Through experiments,it was found that the optimal conditions of these single factors were:the concentration of sulfuric acid was 3.5 mol/L,the liquid-solid ratio was 3 m L/g,the ratio of distiller’s grains to pyrolusite was 0.4,the temperature was 363 K,and the leaching time was 180 min with a stirring rate of 400 rpm.Among these conditions,sulfuric acid concentration,time,temperature,and liquid-solid ratio have significant effects on the leaching rate of manganese ore.（2）Optimization of microwave leaching process by response surface methodology.Microwave leaching experiments were designed using the BBD design method.The model between the leaching rate and the influencing factors was established by Design-Expert software,and the variance analysis and regression coefficient significance test were performed on the response model to ensure the credibility of the established model.The final response surface model gave the optimal reaction conditions for the microwave intensification experiment as follows:sulfuric acid concentr ation 4 mol/L,time 195 min,temperature 357 K,liquid-solid ratio 3 m L/g.The optimization results were verified,and the actual leaching rate obtained was 98.391%,with a standard deviation of 2.33%,which was 5.872%higher than the leaching rate of conv entional experiments.（3）Conduct phase analysis on the reactants before leaching and the leaching residue after the reaction to explore the mechanism of the leaching reaction:A large amount of crude fiber in corn distiller’s grains will be hydrolyzed into reducing sugars with strong reducing ability under the action of sulfuric acid solution.In the sulfuric acid environment,reducing sugars and Mn O₂ undergo redox reactions to form Mn SO₄,which makes manganese continuously reduced and leached.Under the action of microwave heating,due to the different dielectric properties between different parts of the material,the temperature rise is different and the heating is uneven,and rupture occurs from the inside,which increases the reaction area and accelerates the reaction.（4）Through the study of the leaching reaction kinetics,it can be found that the fitting degree of the leaching reaction process and the chemical reaction control model(1-（1-X）^1/3=kt)is relatively high.The apparent activation energy of the leaching reaction under microwave conditions is 47.74 k J/mol.This paper proposes a microwave-enhanced distiller’s dried grain with solubles wet leaching process for pyrolusite,aiming to explore a new clean,efficient and low-energy reduction method of pyrolusite to solve the problem of lack of manganese ore resources.