Herein, we explored a simple approach to using readily available low-cost industrial waste from steel industries known as red-colored iron oxide dust (IOD). After that, it was used for the sunlight-assisted photo removal of another toxic waste material (hexavalent chromium (Cr(VI)) from the aqueous medium showing the photo-Fenton-type mechanism, importantly without using hydrogen peroxide. The photoactive properties of chemically reduced IOD (r-IOD) have been explored to remove toxic Cr(VI) in the presence of two different sources of light (sunlight and artificial bulb light). Kinetic studies and various control experiments have been performed to check the comparative photocatalytic performance of IOD versus r-IOD nanoparticles. The values of the half-life of Cr(VI) removal strongly support the significant influence of the sun on the faster rate for the removal of ∼250 mg L −1 Cr(VI). To maintain the lower pH needed for Cr(VI) reduction, a small quantity of formic acid was used, which can be removed easily by forming CO 2 and H 2 O. The radical trapping experiments and spectroscopic investigations of residue products obtained after the photoreduction process have been explored to support the mechanistic investigation involved in the sunlight-promoted photoreduction of Cr(VI).
Herein, we described a cost-effective, viable methodology for using an iron-based industrial waste material known as iron oxide dust (IOD), also known as Hematite (α-Fe 2 O 3 ) for the synthesis of their chemically reduced magnetic version named r-IOD (Fe 3 O 4 @α-Fe 2 O 3 ). r-IOD showed its visible-light-promoted photoresponsive behavior for the photodegradation of higher concentration (∼1000 mg L −1 ) of five different model dyes (methyl orange (MO), metanil yellow (MY), Congo red (CR), methylene blue (MB), crystal violet (CV), and their mixtures) in the presence of sunlight. Based on kinetic and radical trapping experiments, mechanistic analysis supports the significant involvement of superoxide radicals responsible for the photodegradation. Moreover, different industrial and soil samples were externally spiked with dyes and further analyzed for a similar set of photodegradation experiments to support the viability of the reported procedure, concerning the utilization of waste materials.
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