Progress in photocatalytic degradation of industrial organic dye by utilising the silver doped titanium dioxide nanocomposite

Abstract

Industrial organic dyes represent a significant portion of pollutants discharged into the environment, particularly by the textile industry. These compounds pose serious threats to living organisms due to their high toxicity. Various techniques have been explored for the degradation of organic dyes, among which heterogeneous photocatalysis utilising titanium dioxide (TiO₂) stands out as a promising technology. However, the practical application of TiO₂ as photocatalyst has limitations for the following reasons; First, TiO₂ has a low sensitivity to visible light due to a large band gap which can be 3.2 eV for the anatase polymorph. Second, the recombination rate of photo-induced electron-hole pairs in TiO₂ is very fast. Recent research studies have brought to light that a silver-doped titanium dioxide nanocomposite could be one of the promising answers to these problems. This nanocomposite has garnered significant attention because of its unique features that suggest the manifestation of more effective concepts to minimize the electron-hole recombination and broaden light absorption. This causes Schottky barrier which is essentially created by integrating the silver nanoparticles into titanium dioxide. It is quite significant in decelerating the recombination of the electron-hole pairs, thus increasing photocatalytic activity. Further, it is more effective in that the use of silver also widens the titanium dioxide absorption range to the visible light hence maximizing capture and conversion of broader range of light energies for catalytic reactions. This paper therefore seeks to examine the research background regarding the industrial organic dyes starting with the history of industrial organic dyes before delving into an evaluation of the current and most current research on industrial organic dyes looking at advanced methods of their degradation with specific focus on silver-doped TiO₂ for photocatalytic enhancement. This paper also reviews the experimental work concerning the actual photocatalytic degradation process and presents the factors affecting the performance of silver-doped TiO₂ nanocomposites by eliminating organic dyes from wastewater. It also encompasses a general background into the various synthesis methods used in the preparation of silver-doped TiO₂ nanocomposites. Additionally, challenges and future perspectives in the field are outlined, with a focus on the development of novel strategies to further improve the efficiency and sustainability of silver-doped TiO₂ photocatalysts for industrial organic dye degradation. In conclusion, this review offers a significant outlook on the existing literature concerning the silver-doped TiO₂ nanocomposites for effective photocatalytic degradation of the industrial organic dyes because of the rising pollution level and helping future researchers in seeking the solutions for environmental issues and developing sustainable wastewater treatment.

Keywords: Nanocomposite; Organic dye; Photocatalytic degradation; Silver; Titanium dioxide.

Graphical abstract

Fig. 1

Crystalline structures of (a) anatase, (b) rutile, and (c) brookite. Red spheres represent Ti⁴⁺ ions, and blue spheres represent O²⁻ ions. Yellow lines denote unit cells, showing the different crystal structures: anatase's open tetragonal structure with efficient electron pathways, rutile's dense tetragonal configuration, and brookite's complex orthorhombic arrangement, contributing to the variations in photocatalytic properties.

Fig. 2

Mechanism of photocatalytic activity of TiO₂ in the presence of UV light.

Fig. 3

Illustrates the process of charge transfer in Ag doped TiO₂ photocatalyst in photocatalytic degradation.