Highly adsorptive and regenerative magnetic TiO2 for natural organic matter (NOM) removal in water

Abstract

Abstract Herein, we demonstrate the ability of magnetic titanium dioxide (Fe3O4@SiO2@TiO2) to rapidly remove natural organic matter (NOM) from water by adsorption and thereafter be effectively regenerated by either ultraviolet light or illumination using a solar simulator. NOM adsorption on magnetic TiO2 was found to rapidly reach equilibration, with a majority of the organic matters adsorbed within the first 5 min. Studies at a neutral pH range, with a magnetic particle loading of 3 g L−1, showed that approximately 65% and 39% of NOM was removed from synthetic water (SW) and natural water (NW), respectively. The trihalomethanes formation potential (THMFPs) of both synthetic and natural waters after treatment was either within the range or lower than the acceptable Australian limit (250 μg L−1). These treatment levels were sustained throughout the five adsorption–regeneration cycles. By lowering the pH value to 6 and 5, the adsorption performance of the magnetic TiO2 was significantly enhanced (approximately 10% increment for every unit decrease in pH) and the THMFP values of the treated NW were reduced to 142 ± 1 μg L−1 and 123 ± 1 μg L−1, respectively. This result shows the role of surface charge and electrostatic interactions in NOM removal.