Goethite-Activated Carbon as a Highly-Effective Persulfate Activator for Disinfection

In this work, goethite modified activated carbon (α-FeOOH@AC) was synthesized by wetness-impregnation and used as a persulfate (S2O82-, PS) activator to inactivate Escherichia coli in water. Surficial analysis displayed that micron-sized (0.5 to 1 μm) α-FeOOH particles were uniformly distributed on AC and structural ferric irons [Fe(III)] in the α-FeOOH matrix were partially reduced to ferrous iron [Fe(II)] by the reductive hydroxyl groups of AC. The surface-bonded Fe(II) facilitated PS to generate sulfate and hydroxyl radicals (SO4·- and ·OH) for effective disinfection by destructing bacterial membrane. Therefore, a higher inactivation efficiency of 6.0 log was achieved in the α-FeOOH@AC-PS system as compared to 3.1 and 0.4 log in the AC-PS and α-FeOOH-PS systems, respectively. Moreover, Escherichia coli did not regrow in the α-FeOOH@AC-PS system within 48 h, indicating its persistent growth inhibition by radicals. The α-FeOOH@AC system also had high inactivation efficiency over a broad range of pH (3 to 11) and excellent stability in the cycling test. In addition, the spent α-FeOOH@AC was amenable for effective regeneration by eliminating surficial iron oxides and subsequent reloading of α-FeOOH through wetness-impregnation with a regeneration rate up to 96.7%. These results demonstrated that α-FeOOH@AC can effectively and stably activate PS for inactivating bacteria in water