Mechanism of continuous desulfurization by peroxymonosulfate activated by grain-boundary electron transfer in waste pyrite.

The emission of high-concentration sulfur dioxide (SO2) from metallurgical flue gas and the environmental risks associated with pyrite solid waste accumulation have become critical bottlenecks to sustainable industrial development. To address the efficiency decay in traditional homogeneous Fe2+/peroxymonosulfate (PMS) systems caused by irreversible iron consumption, this study develops a heterogeneous catalytic system using waste pyrite, establishing a sustainable and highly efficient flue gas desulfurization process. Experimental results demonstrate that under conditions of 0.1 g/L pyrite, 0.2 M PMS, 38-75 μm pyrite particle size and 20 °C, the system achieves 100 % desulfurization efficiency for up to 660 min, representing a 5.5-fold longevity improvement over conventional Fe2+ systems. Pyrite facilitates Fe(III)/Fe(II) self-cycling via sulfur-vacancy-mediated electron transfer, enabling continuous persulfate activation to generate multiple reactive species, including 1O2, SO4•-, and Fe(IV) = O. Meanwhile, its crystalline controlled-release mechanism prevents excessive Fe2+ consumption, thereby sustaining long-term desulfurization performance. The spin-restriction effect and lattice oxygen act synergistically to promote a 1O2-dominated non-radical pathway, while the acidic environment and gas-liquid mass transfer properties suppress •OH formation, resulting in a unique oxidation mechanism tailored for flue gas desulfurization. This work provides both theoretical insights and a technical paradigm for the resource utilization of metallurgical solid waste and synergistic treatment of multi-pollutant flue gas.