Electron shuttle of carboxyl boosted Fe(III)-anchored carboxylated cellulose activating sodium perborate for organic pollutant abatement

The traditional Fenton application is limited by the disproportionation of hydrogen peroxide (H2O2) and the tardy reduction of Fe(III). To conquer these issues, we construct an enhanced Fenton-like process using a composite of citric acid-carboxylated microcrystalline cellulose complexing with Fe(III) (CA-Fe(III)@MCC) to activate sodium perborate (SPB), which can effectively eliminate antibiotic sulfamethoxazole (SMX, 89.2%, 0.035 min-1). The CA-Fe(III)@MCC composite significantly enhances the circulation of Fe(III)/Fe(II), leading to the generation of hydroxyl radicals and perboric radicals with excellent structural stability and minimal Fe leaching during CA-Fe(III)@MCC/SPB process. Systematic investigations reveal that the introduced carboxyl groups not only anchor Fe(III) to prevent its deactivation and leaching, but also regulate the coordination environment and serve as electron shuttles, driving the formation of reactive species and reduction of Fe(III). This process presents a novel, environmentally friendly, and sustainable strategy for utilizing natural cellulose and its industrial biomass product in advanced oxidation processes.