Postsynthesis of β-FeOOH/SBA-15 composites via mild ozone treatment: Effective surfactant removal and perfect property preservation for enhanced arsenic adsorption

Abstract

Removal of surfactant templates from freshly prepared mesoporous metal-loaded silica materials by calcination often induces structure shrinkage, loss of functional groups and metal oxide sintering. This work reported the use of ozone treatment for postsynthesis of Fe-containing SBA-15 with the surfactant almost completely removed and the other properties perfectly maintained. The ozone treatment could handle large sample quantities and treatments at 40–80 °C for 1–3 h could effectively remove the triblock copolymer P123. The hydroxyl (OH) groups of SBA-15, the high dispersion state of Fe at low loadings and the intrinsic nature of β-FeOOH at high loadings kept intact. The arsenic (As(III)) adsorption performances of the as-made, calcined and ozone-treated samples with high Fe loadings were compared. Both the adsorption rate and capacity were boosted by the ozone-treated samples. Their adsorption kinetics followed the pseudo-second-order kinetic model and their adsorption isotherms were Langmuir-type. Complete removal of As(III) and high adsorption capacity (up to 30.4 mg/g) could be reached on the ozone-treated samples. The effects of common co-existing anions on adsorption were clarified. The ozone-treated samples could be regenerated with high cyclic performance. The adsorption mechanism was associated with both electrostatic interaction and surface complexation. This study would provide guideline for surfactant removal and broaden the applicability of mesoporous metal-containing silica wherein OH groups, highly dispersed metal species or active metal hydroxides are necessities.