Surface-Modified Pyrite with a Schwertmannite Shell: Enhancing the Application Performance of Pyrite-Mediated Advanced Oxidation Processes in a Continuous-Flow System

Abstract

Most of the current pyrite-based advanced oxidation processes (AOPs) rely on a homogeneous catalytic mechanism mediated by leached Fe 2+ /Fe 3+ from pyrite oxidation. While in continuous-flow water treatment processes, the continual Fe 2+ /Fe 3+ efflux limits pyrite dissolution and the corresponding hydroxyl radical ( • OH) generation for contaminant degradation. To solve this bottleneck problem, a pyrite−schwertmannite (Sch) binary mineral named Sch@py(1:5) was prepared through a simple chemical method where Sch serves as a surface shell coating on the pyrite core. Compared to the pyrite−H 2 O 2 system, the Sch@py(1:5)−H 2 O 2 system exhibits significantly slighter iron leaching and was verified to possess a heterogeneous Fenton process dominant • OH generation pathway, thereby eliminating the reliance of the Sch@py(1:5)−H 2 O 2 system on Fe 2+ /Fe 3+ concentrations in water. Through shielding H 2 O 2 from being directly decomposed by pyrite and the associated Fenton sludge, the Sch−pyrite core−shell structure improves the utilization efficiency of H 2 O 2 5.18 times and 1.15 times than that of the pyrite−H 2 O 2 system in the presence and absence of 0.21 g of Fe•L −1 Fenton sludge, respectively. Furthermore, the Sch shell endows pyrite with the coupling oxidation and adsorption capacity for organoarsenic-bearing contaminants, thus enabling the Sch@py(1:5)-filled fixed bed to purify 2451 BV of highly concentrated (0.1 mg of As•L −1 ) organoarsenic wastewater at a flow rate of 30 BV•h −1 . This study provides a novel strategy to improving the application potential of pyrite, the commonly existing but underutilized mineral resource, in practical water treatment processes.

Sulfur Vacancies in Pyrite Trigger the Path to Nonradical Singlet Oxygen and Spontaneous Sulfamethoxazole Degradation: Unveiling the Hidden Potential in Sediments

“…Natural pyrite (FeS 2 ) is an abundant iron sulfur mineral widely distributed in subsurface environments. 9 The weathering and oxidation of pyrite involve complex processes, such as adsorption, redox reactions, and interface interactions, which significantly affect the fate of coexistent pollutants, such as SMX. 10 Pyrite, beyond its role as a mineral, acts as a semiconductor, showing promise as a photocatalyst in pollutant degradation.…”