Preparations of cyclodextrin polymer and MgO jointly entrapped iron(III)-TAML catalysts for the removal of aromatic pollutants in water

Abstract

Iron(III)-tetra-amido-macrocyclic (Fe(III)-TAML) activators generally activate H2O2 to efficiently degrade electron-rich pollutants (e.g., phenols) in water under basic conditions, though Fe(III)-TAML is readily demetallized and inactivated under acidic or nearly neutral conditions. Fe(III)-TAML/H2O2 systems often display low reactivity toward electron-deficient pollutants (benzenes) widespread in water. Fe(III)-TAML catalysts with improved pH adaptations and substrate spectra are highly desirable. Herein, we proposed one-pot preparations of cyclodextrin polymer (CDP) and MgO jointly supported Fe(III)-TAML catalysts for the removal of various aromatic contaminants in water. The composite catalysts exhibited typical polymeric network structure of CDP, embedded with basic MgO/Mg(OH)2 particles and three different Fe(III)-TAML species. The composites repeatedly used for 3–4 times still activated H2O2 to completely remove 4-chlorophenol in water during initial pH 2.0–9.0 conditions or in the presence of main water constituents. Despite low Fe(III)-TAML loadings (0.03%–0.10%), these composites displayed great pH adaptations and diverse reactive regions toward organic compounds, compared to other supported catalysts containing 0.24%–1.27% Fe(III)-TAML. Column experiments demonstrated that the composite/H2O2 completely removed electron-rich 4-chlorophenol and electron-deficient benzenes in simulated groundwater. This study indicates that taking CDP as a support may open new prospects for the design of supported catalysts.