Simultaneous photocatalytic removal of organic dye and heavy metal from textile wastewater over N-doped TiO2 on reduced graphene oxide

Abstract

Methylene blue (MB) and hexavalent chromium(Cr(VI)) are hazardous pollutants in textile waste and cannot be completely removed using conventional methods. So far, there have been no specific studies examining the synthesis and activity of N-TiO₂/rGO as a photocatalyst for removing MB and Cr(VI) from textile wastewater. This work especially highlights the synthesis of N-TiO₂/rGO as a photocatalyst which exhibits a wider range of light absorption and is highly effective for simultaneous removal of MB-Cr(VI) under visible light. Titanium tetrachloride (TiCl₄) was used as the precursor for N-TiO₂ synthesis using the sol-gel method. Graphite was oxidized using Hummer's method and reduced with hydrazine to produce rGO. N-TiO₂/rGO was synthesized using a hydrothermal process and then analyzed using several characterization instruments. The X-ray diffraction pattern (XRD) showed that the anatase N-TiO₂/rGO phase was detected at the diffraction peak of 2θ = 25.61. Scanning electron microscopy and transmission electron microscopy (SEM-EDS and TEM) dispersive X-ray spectrometry images show that N-TiO₂ particles adhere to the surface of rGO with uniform size and N and Ti elements are present in the N-TiO₂/rGO combined investigated. Gas absorption analysis data (GSA) shows that N-TiO₂/rGO had a surface area of 77.449 m²/g, a pore volume of 0.335 cc/g, and a pore size of 8.655 nm. The thermogravimetric differential thermal analysis (TG-DTA) curve showed the anatase phase at 500-780 °C with a weight loss of 0.85%. The N-TiO₂/rGO composite showed a good photocatalyst application. The photocatalytic activity of N-TiO₂/rGO for textile wastewater treatment under visible light showed higher effectiveness than ultraviolet light, with 97.92% for MB and 97.48% for Cr(VI). Combining N-TiO₂ with rGO is proven to increase the light coverage in the visible light region. Removal of MB and Cr(VI) can be carried out simultaneously and results in a removal efficiency of 95.96%.

Keywords: N-TiO(2)/rGO; Removal of MB and Cr(VI); Textile wastewater; Visible light photocatalyst.