Abstract

The treatment of real wastewater effluent can be complicated due to the coexistence of heavy metals and organic pollutants. To investigate the simultaneous reduction of hexavalent chromium (Cr (VI)) and degradation of methyl orange (MO) dye, a photo-Fenton combination method was used over novel fibrous silica iron (FSFe) catalysts instigated from three different iron oxide precursors-maghemite (Fe2O3), magnetite (Fe3O4), and goethite (FeOOH) via a microemulsion process. The study showed the successful incorporation of iron that dispersed homogenously on the surface of the synthesized fibrous silica catalysts. The high rearrangement of Si-O-Fe bonds was found to minimize the band gap and contributed to the increase of catalyst's surface area. The degradation of MO was enhanced in the photo-Fenton system due to the high number of electrons supplied to the Fenton cycle which increase the production of hydroxyl radicals. However, the repulsion effect between negatively charged catalyst and excessive production of OH- hindered the reduction of Cr (VI). The FSFe2O3 exhibited the highest reduction of Cr (VI) and degradation of MO due to its small band gap, appropriate band position, and high concentration of Fe3+ ions compared to other catalysts. The scavenger studies confirmed that e(-) is the primary species responsible for the removal of Cr (VI), while for MO is mainly controlled by the hydroxyl radicals in bulk solution (center dot OHbulk), and a mechanism of photo-Fenton over FSFe2O3 catalyst was proposed. The ability of FSFe to remove both pollutants was successfully maintained for five runs, demonstrating its potential for treating dual pollutants in wastewater.