Facilitating calcium sulfite oxidation during flue-gas desulfurization for efficient sulfur utilization using a robust MnTiO3 perovskite

Abstract

Accelerating the oxidation of calcium sulfite is extremely crucial for the limestone/gypsum method of flue-gas desulfurization by enhancing the desulfurization efficiency, preventing subsequent SO2 release, and generating pure calcium sulfate as a value-added product for downstream utilization. In this work, MnTiO3 perovskite nanodisks with high crystallinity and good thermal stability were synthesized by a hydrothermal method. The highly stabled exposed 001 facets of the MnTiO3 catalyst give rise to its catalytic reactivity which promote the electron transfer in sulfite oxidation process thus effectively generated reactive oxygen species (O2−, OH, and SO4−) to accelerate the sulfite oxidation cycle. Compared with non-catalytic oxidation reactions, the calcium sulfite oxidation rate and calcium sulfate yield were increased by 4.3 times and 34.02% by using MnTiO3, respectively. After four cycles, the calcium sulfite oxidation rate was only 9.57% lower than that in the first cycle, and Mn leaching was minimal. To simulate actual usage scenarios, the extrusion method was employed to prepare a molded catalyst for facile separation from the desulfurization slurry, which revealed acceptable performance at a dosage of 10 g·L−1. The proposed MnTiO3 perovskite catalyst is non-toxic, cost-effective, convenient to synthesize, and recyclable, providing new possibilities for sulfur reclamation during flue-gas desulfurization.