Glycerol-Mediated Synthesis of Nitrogen-Doped TiO2 With Excellent Adsorption and Photocatalytic Activity for Remazol Red Dye Removal

Abstract

This paper reports the synthesis, characterization, and application of nitrogen-doped TiO2 (N-TiO2) as an adsorbent and photocatalyst for the removal of Remazol Red Dye (RRD) from aqueous solution. The N-TiO2 was prepared via a sol-gel technique using glycerol and water as solvent mixture and urea as N-precursor. The efect of N:Ti molar ratio (15:1, 20:1, and 25:1) and calcination temperature (300, 400, and 500°C) was evaluated on the structural, morphological, optical, and electronic, textural properties as well as the photocatalytic performance of the N-TiO2 nanomaterials. The results demonstrated that the N:Ti molar ratio plays an important role in the formation of crystalline N-doped TiO2 photocatalysts. All the synthesized N-TiO2 were anatase phase with enhanced visible light absorption, displaying narrow bandgaps (2.64-2.50 eV), small particle sizes ranging from 23.1-25.2 nm, and specifc surface area ranging from 72.33 to 252.69 m2 /g. The N:Ti molar ratio and calcination temperature play a crucial role in pre-equilibrium adsorption and photocatalytic removal of RRD. The N-TiO2 with N:Ti molar ratio of 25:1 was able to remove 95.85% of RRD was compared to merely 36.06% by the N:Ti, 15:1, within 30 min of the adsorption process. However, the photocatalytic removal by N:Ti, 15:1 of RRD was drastically enhanced to 100% within 30 min of photoreaction compared to 99.44% by N:Ti, 25:1. The RRD removal via adsorption by N:Ti, 25:1 was increased from 36.06% to 78.53% and 96.05%, increasing calcination temperatures from 300 to 400 and 500°C, respectively. The RRD removal via photocatalysis was 87.30%, 97.41 and 99.44% when the photocatalyst was calcined at 300, 400 and 500°C, respectively. The outcome of this work suggests that N-TiO2 has good potential when employed as an adsorbent and photocatalyst for RRD removal from textile wastewater.