Photodegradation of Rhodamine B using gallium hybrids as an efficient photocatalyst

Abstract

Keeping in view the toxicity of the Rhodamine B, the present study is designed to remediate the water loaded with toxic dyes using gallium oxide and gallium hybrids as photocatalyst. Precipitation coupled with sonochemical method is adopted for the synthesis of gallium oxide while the post grafting method is adopted for the synthesis of gallium hybrids with the indole and its derivatives. FTIR spectra showed the characteristic absorption bands of gallium oxide and gallium hybrids at 400-700 cm^-1 and 1400-1600 cm^-1. SEM and XRD showed the micro-sized rectangular rod-shaped gallium oxide with rhombohedral geometry. The average crystallite size of gallium hybrids was 26-32 nm calculated using the Debye Scherrer and Williamson-Hal models. The BET isotherm of gallium hybrids revealed the adsorption type-IV and hysteresis loop (H3) proposing multilayer and mesoporous structures with increase in surface area from 26 m²/g of gallium oxide to 31 m²/g of gallium-indole, 35 m²/g of gallium-methyl indole, and 37 m²/g of gallium-carboxylic indole. XPS showed the presence of gallium (3-14%), oxygen (28-32%), nitrogen (23-46%), and carbon (9-46%). The gallium oxide and gallium hybrids showed 47-72% optimum degradation of Rhodamine B under 2 h of illumination at pH 7 and 0.03 mg/L. The degradation rate followed a Langmuir-Hinshelwood model with R² > 0.9.

Keywords: Gallium oxide; Indole; Langmuir-Hinshelwood model; Photodegradation.