Reductive leaching of pyrolusite using orange peel as a reducing agent

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 ۲۵ to ۹۵ °C, the weight ratio of reducing agent to pyrolusite (R/P) in the range of ۰ to ۲ (w/w), and the concentration of sulfuric acid in the range of ۰.۰۵ to ۰.۲۵ 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 ۲۵ to ۹۵ °C, Mn recovery increases from ۰.۵% to ۵۲.۵%. Also Mn recovery with a two-step increase in ۰-۰.۱ and ۰.۱-۱.۵ of the R/P indicates a jump of ۲۸.۵% and ۱۹.۰%, 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 ۹۸.۱% under optimum conditions (temperature of ۹۰ °C, sulfuric acid concentration of ۰.۱ M, and R/P ratio of ۱.۵ (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.

Keywords:

Pyrolusite , Manganese reductive leaching , Orange peel , Kinetic evalution , Avrami model