Accelerating reduction of ferric iron by tourmaline for efficient H2O2 activation in removing aqueous organic pollutants.

The efficient generation of active ferrous ions is essential for the continuous degradation of organic pollutants in the Fenton system; however, this process is significantly hindered by the sluggish reduction of ferric ions. In this study, commercial tourmaline (Tr), a natural silicate mineral, was employed to overcome this kinetic limitation. The Tr/Fe3+/H2O2 (Tr + Fe3+ + H2O2) system achieved an accelerated redox cycle of Fe3+/Fe2+, rapid decomposition of H2O2, and enhanced removal of 2,4,6-trichlorophenol (TCP) within 30 min. Compared to the Fe3+/H2O2 system, the Tr/Fe3+/H2O2 system improved the degradation efficiency by 43-fold, even with low concentrations of H2O2 (0.5 mM) and Fe3+ (0.05 mM). Moreover, the system generated free hydroxyl radicals (•OH), super oxygen (O2•-), and singlet oxygen (1O2), which contributed to the effective removal of various pollutants, including organic dyes, pharmaceuticals, and phenolic compounds. In-situ FTIR and XPS analyses revealed that the iron cycle was facilitated by surface Si-OH sites through the formation of Si-O-Fe bonds. Tourmaline also exhibited excellent recyclability and sustained reactivity in five consecutive experimental runs. Overall, this study presents a promising strategy to address the rate-limiting step of Fe3+/Fe2+ conversion and promotes the application of natural minerals in iron-based advanced oxidation processes (AOPs).