Fabrication of Ca-doped TiO2 for enhanced methylene blue degradation under UV-Vis irradiation
Atol Mondal, Sumon Islam, SK. Methela Zaman, Marzia Sultana, Md. Minhaz Abedin, Chakraborty Ak, Md. Mahfuzur Rahman, Md. Hafezur Rahaman, Mst. Sumaia Aktar Sumi, Alam S.M. Nur
Abstract
Research continues to improve the dye degradation performance of TiO 2 nanoparticles (NPs) through doping, tailoring, or modifying the lattice structure. A series of Ca–TiO 2 (Ca ions 0.5–2.0 wt%) photocatalysts prepared by wet impregnation method were studied for methylene blue (MB) degradation under UV-Vis irradiation, using different factors, including contact time, pH, initial dye concentration, and dosages. The photocatalyst samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Characterization results revealed the successful doping of Ca ion on the TiO 2 surface, and Ti, O, and Ca were identified by EDX analysis as being present in the Ca-doped TiO 2 sample. Calcium improved titania's charge separation capability, favoring the formation of more hydroxyl radicals during irradiation. Another important effect of Ca is the lowered bandgap energy of TiO 2 , which enhances the light absorption capacity into the visible regions. The photocatalytic performance varied with calcium ions content in the prepared catalysts, and a moderate amount showed the best activity. 1 wt% Ca–TiO 2 exhibited a maximum MB degradation of 79.65 % with TOC removal of 52.36 % and followed the pseudo-first-order reactions kinetics with a rate constant of 0.0087 min −1 . Notably, both the degradation performance and rate constant of 1 wt% Ca-TiO 2 catalysts were much superior to pure TiO 2 under the same reaction conditions. This finding suggests that Ca-TiO 2 NPs could be a highly effective photocatalyst for the ecologically benign degradation of color compounds in textile wastewater. • Ca-doped TiO 2 photocatalysts were synthesized by wet impregnation method. • Characterization confirmed the incorporation of Ca ions into TiO 2 matrix. • Ca ions dopant successfully decreased the bandgap energy. • Maximum 79.65 % MB degradation was obtained for 1.0 wt% Ca ions under UV-Vis irradiation within 3 h. • Ca-doped TiO 2 showed much higher dye degradation activity than pure TiO 2 .