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.