Microwave efficient extraction of manganese from low-grade pyrolusite by pyrite reduction acid leaching process

Abstract

With the continuous economic and social development of China, the demand for pyrolusite has increased tremendously, accompanied by a decrease in high-grade pyrolusite (HGP). Thus, it is urgent to find viable alternatives, such as low-grade pyrolusite (LGP). Currently, a relatively mature process technology is a one-step acid leaching of manganese (Mn) from pyrolusite using pyrite (PY) as a reducing agent. While the method can achieve a relatively high leaching efficiency of Mn at atmospheric pressure, it requires a significant amount of time. To pursue maximum effectiveness and efficiency, here we applied microwave leaching technology to the one-step acid leaching process to the extraction of Mn from LGP, and PY as a reducing agent. The results showed that the leaching efficiency of Mn reached 96.2% at time = 150 min, agitation speed = 400 rpm, temperature = 363 K, acid concentration = 1.5 M, liquid-solid ratio = 10: 1 (mL: g), and SLGP-SPY mass ratio = 10: 2. Furthermore, the kinetic analysis showed that the chemical reaction control model (1-(1-X)1/3 = kt) can be used to explain the mechanism of the microwave leaching process. Finally, according to the Arrhenius equation, the apparent activation energy (Ea) for the microwave leaching process was calculated as 44.8 kJ/mol. This work provides the preliminary theoretical and technical basis for recovering Mn from LGP. In summary, these results imply that LGP could be effectively utilized and developed by microwave heating technology in the future.