The effect of surface charge on photocatalytic degradation of methylene blue dye using chargeable titania nanoparticles

Herein, a simple approach based on tailoring the surface charge of nanoparticles, NPs, during the preparation to boost the electrostatic attraction between NPs and the organic pollutant was investigated. In this study, chargeable titania nanoparticles (TiO2 NPs) were synthesized via a hydrothermal route under different pH conditions (pH = 1.6, 7.0 and 10). The prepared TiO2 NPs were fully characterized via various techniques including; transmission electron microscopy (TEM), X-ray diffraction (XRD), N-2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible spectroscopy (UV-Vis) and dynamic light scattering (DLS). The influence of the preparation pH on the particle size, surface area and band gap was investigated and showed pH-dependent behavior. The results revealed that upon increasing the pH value, the particle size decreases and lead to larger surface area with less particles agglomeration. Additionally, the effect of pH on the surface charge was monitored by XPS to determine the amount of hydroxyl groups on the TiO2 NPs surface. Furthermore, the photocatalytic activity of the prepared TiO2 NPs towards methylene blue (MB) photodegradation was manifested. The variation in the preparation pH affected the point of zero charge (pH(PZC)) of TiO2 NPs, subsequently, different photocatalytic activities based on electrostatic interactions were observed. The optimum efficiency obtained was 97% at a degradation rate of 0.018 min(-1) using TiO2 NPs prepared at pH 10.