Double-Layer Coated TiO2 Structures Derived from an Agro-Industrial Biowaste: A Comprehensive Characterization for Water Treatment

Abstract

Recently, the use of agro-industrial biowaste, particularly rice husk (RH), has emerged as a promising option for producing value-added products. This low-cost solid waste is considered a potential multi-dopant source and a green approach for preparing photocatalysts used in water treatment. Double-layer coated TiO2 (RH2xTiO2) structures derived from RH were synthesized through the sol-gel process. RH acted as both an agro-industrial biowaste template and a multi-dopant ion source during the double-layer coating process of TiO2. The sacrifice of this template in the calcination process resulted in the formation of a self-doped catalyst containing silicon, carbon, nitrogen, and sulfur. The characterization features of the photocatalyst were carried out by using XRD, SEM, XPS, BET, and UV-DRS spectroscopic techniques. The results of XRD analysis revealed that a mixture of anatase and rutile phases of TiO2. The calculated crystallite particle size of RH2xTiO2 structures was 18.4 nm. The SEM image of the RH2xTiO2 structures exhibited a variety of polyhedral morphologies with cracks. The bang gap energy (Ebg) of the RH2xTiO2 structures was 2.92 eV. BET analysis indicated that the RH2xTiO2 specimen exhibited a Type IV isotherm, and the surface area was 77 m2/g. The photocatalytic activity of RH2xTiO2 structures was evaluated for the degradation of 4-nitrophenol (4-NP) as a model pollutant under UV irradiation.