Investigating adsorption/photocatalysis of organic contaminants by Fe3O4–GO, Fe3O4–C3N4, and Fe3O4–GO-C3N4 heterojunctions

Abstract

Water pollution by contaminants such as dyes and drugs is a serious environmental problem. Currently, the objective is to develop materials that are effective in removing these contaminants. Graphene oxide (GO) and graphitic carbon nitride (g-C₃N₄) have been used as adsorbents for the efficient removal of organic pollutants and are useful to improve the photoactivity of iron oxide (Fe₃O₄). In this work, the Fe₃O₄, Fe₃O₄–C₃N₄, Fe₃O₄–GO, and Fe₃O₄–GO–C₃N₄ powders were structurally characterized by the X-ray diffraction technique and morphologically by the field emission scanning electron microscopy technique. Optical properties were studied using UV–visible spectroscopy and VSM analysis was performed to determine the remanence magnetization. The adsorption and photocatalysis were tested against methylene blue (MB), methyl orange (MO) and ketoprofen. XRD patterns for Fe₃O₄ and heterojunctions showed Fe₃O₄ formed as a single phase. As for morphological observation, Fe₃O₄ and g-C₃N₄ are formed by nanoparticles without defined morphology, while GO is formed by sheets. As for the VSM analysis, all samples show ferromagnetic behavior. The Fe₃O₄, Fe₃O₄–C₃N₄, Fe₃O₄–GO, and Fe₃O₄–GO–C₃N₄ samples have a bandgap of 2.07, 2.21, 2.14, and 2.19 ​eV, respectively. Therefore, all samples absorb visible radiation in waves greater than 560 ​nm. Heterojunctions containing g-C₃N₄ completely adsorb the MB and MO dyes, being necessary to extend the activity time when concentration increases or when the dyes are put together. Both Fe₃O₄ and Fe₃O₄–GO have photocatalytic properties toward MO dye. All materials studied in this manuscript have good adsorption and photocatalytic capacity against the anti-inflammatory drug ketoprofen.