Photocatalytic Degradation of Recalcitrant Pollutants of Greywater

Abstract

These days, many countries have a water shortage and have limited access to clean water. To overcome this, a new treatment is emerging, namely, the photocatalytic processing of greywater. Photocatalytic processes to remove the organic matter from different greywater sources are critically reviewed. Their efficiency in degrading the organic matter in greywater is scrutinized along with factors that can affect the activity of photocatalysts. Modified TiO2, ZnO and TiO2 catalysts show great potential in degrading organic materials that are present in greywater. There are several methods that can be used to modify TiO2 by using sol-gel, microwave and ultrasonication. Overall, the photocatalytic approach alone is not efficient in mineralizing the organic compounds, but it works well when the photocatalysis is combined with oxidants and Fe3+. However, factors such as pH, concentration and catalyst-loading of organic compounds can significantly affect photocatalytic efficiency.

Effect of phenol concentration on the photocatalytic performance of ZnO nanoparticles

“…It has been reported that, with high initial concentrations, the photocatalytic performance can be diminished, whereas low concentrations help maintain, and even to improve, the photoactivity of the catalyst. This can be attributed to the adsorption of the pollutant over the surface of the photocatalysts, saturating it and hindering the generation of hydroxyl radicals (OH•), which are usually the chemical species that rule photocatalytic tests 45,46 …”

“…This can be attributed to the adsorption of the pollutant over the surface of the photocatalysts, saturating it and hindering the generation of hydroxyl radicals (OH•), which are usually the chemical species that rule photocatalytic tests. 45,46 Fluorescence tests have been developed as a fast analysis for determining the generation of hydroxyl radicals in aqueous media (Supporting Information, Scheme S1). When comparing the half-life time obtained with the new ZnO and the recovered one used in the third reaction cycle, the degradation of the phenol becomes slower; consequently, a longer time is required to achieve half the degradation of its initial concentration (either 5 or 50 ppm).…”

Advances in Hybrid Composites for Photocatalytic Applications: A Review

“…A Photocatalytic process occurs when the light interacts with the surface of semiconductor materials, the so-called photocatalysts, allowing the photo redox process. During this process, there must be at least two simultaneous reactions occurring, oxidation from photogenerated holes and reduction from photogenerated electrons ( Figure 3 ) [ 36 , 37 , 38 ].…”

Tin Oxide Materials for Industrial Wastewater Treatment: Promising Adsorbents and Catalyst

“…This catalytic activity stems from the generation of electron-hole pairs upon exposure to UV light, which subsequently triggers redox reactions leading to the breakdown of complex pollutant molecules into simpler and less harmful compounds [18]. This photocatalytic degradation mechanism presents a sustainable and energy-efficient route to neutralize recalcitrant pollutants, showcasing the potential of these materials to transform the landscape of wastewater treatment practices [18,19].…”