In-process control of manganese dithionate in the manganese ore-based wet flue gas desulfurization coupled with efficient manganese leaching

Abstract

Manganese ore-based wet flue gas desulfurization (MFGD) is a resourcing technology capable of simultaneously reutilization flue gas sulfur dioxide (SO2) and green, low-carbon manganese leaching. However, the by-product manganese dithionate (MnS2O6) greatly affects the use of desulfurization liquid. In this study, the iron introduced MFGD process to achieve the in-process control of MnS2O6 was proposed and systematically studied. The results revealed that the Fe(III) greatly enhanced the MnS2O6 degradation by manganese dioxide (MnO2), which works principally as an oxidant, and generates certain hydroxyl oxidize iron (FeOOH) to promote the MnS2O6 degradation. Kinetic studies revealed that the Fe(III) enhanced MnS2O6 degradation by manganese oxide ore (MnOO) occurred mainly on the surface of solid, and the apparent activation energy (Ea) was reduced to 43.56 kJ mol−1. The Fe(III) could be also incorporated into the MFGD process to achieve the in-process control of MnS2O6. According to the operational experiments, 5.00 g L−1 of Fe(III) in the MnOO slurry could reduce the MnS2O6 in the desulfurization liquid from 5.34 g L−1 to 1.75 g L−1 and without any noticeable negative effect. This study provides an applicable option for the low-cost and simple control of MnS2O6 of the MFGD technology, and it will also support the utilization of the low-grade manganese ore.