Heliyon (Oct 2024)
Photocatalysis as a pre-discharge treatment to improve the effect of textile dyes on human health: A critical review
Abstract
The increasing need for dyes in the textile sector, has led to significant environmental consequences such as natural water contamination. Textile dyes in water can hinder algae and aquatic plant growth, break down into harmful intermediates, and affect the aquatic food chain. Terrestrial animals may also encounter these dyes through consumption or exposure. Cationic and anionic dyes like methylene blue, malachite green, rhodamine B, methyl orange, eosin y and methyl red can cause skin irritation, carcinogenicity, mutagenicity, and teratogenicity. Therefore, the presence of these dyes in natural and wastewater streams pose significant threats to the aquatic ecosystems, ecological systems and human health. Effective management and remediation of textile dye effluents is crucial to mitigate these risks. Although regulatory bodies like ecological and toxicological association of the dyestuffs manufacturing Industry (ETAD) are working on addressing these risks, more challenges still persist due to nature of textile dyes, lack of enforcement of these regulations on textile dye industries etc. and many more. This review explores alternative processes for textile dye effluents treatment before their release to the environment. The aim of the review is to recommend photocatalysis as a suitable preliminary treatment technique for textile effluents before their release to the environment. Photocatalysis stands out amongst other advanced oxidation processes (AOPs) processes as it is a promising approach that researchers worldwide are embracing. It is a process that converts organic pollutants into less harmful substances using light and a photo-excitable catalyst. Both TiO₂ and ZnO are widely used photocatalysts and have shown effectiveness towards dye degradation. Their degradation efficiencies depend on pH, concentration of dye, dosage, time and the type of light. These photocatalysts are reusable and have OH radicals as the most active species during the photodegradation process. Recent studies have shown that photocatalysis, either alone or in combination with other methods like UV or H₂O₂, offers a practical preliminary treatment option for various industrial effluents, enhancing the degradability of complex dyes and pollutants.
