Shahrood University of Technology Journal of Mining and Environment 2251-8592 14 4 2023 10 01 Reductive leaching of pyrolusite using orange peel as a reducing agent 1307 1319 2899 10.22044/jme.2023.13206.2414 EN Pedram Ashtari Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran. Saeid Karimi Department of Metallurgy and Materials Engineering, Hamedan University of Technology, Hamedan, Iran. Seyyede Atefeh Hosseini Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran. Journal Article 2023 06 01 In this research work, the reductive leaching of pyrolusite in a sulfuric acid medium with the aid of orange peel as a reductant was investigated. The important parameters affecting the leaching process include temperature in the range of 25 to 95 °C, the weight ratio of reducing agent to pyrolusite (R/P) in the range of 0 to 2 (w/w), and the concentration of sulfuric acid in the range of 0.05 to 0.25 M. According to the results, the parameters of temperature and the R/P are more significant in the reductive leaching process. With increasing temperature from 25 to 95 °C, Mn recovery increases from 0.5% to 52.5%. Also Mn recovery with a two-step increase in 0-0.1 and 0.1-1.5 of the R/P indicates a jump of 28.5% and 19.0%, respectively. Sulfuric acid concentration shows its effect by supplying sulfate and hydrogen ions in the leaching process. The successful use of orange peel as a reductant was confirmed by achieving a manganese dissolution efficiency of 98.1% under optimum conditions (temperature of 90 °C, sulfuric acid concentration of 0.1 M, and R/P ratio of 1.5 (w/w)). Kinetic investigations showed that the shrinking core model could not be used to determine the leaching mechanism of pyrolusite in the presence of fruit peel reductant. Avrami's kinetic model with very high fitting accuracy was used to determine the kinetic model of pyrolusite leaching. https://jme.shahroodut.ac.ir/article_2899_a323e8ec907092b322e925d304c80712.pdf