Advances in the Application of Nanocatalysts in Photocatalytic Processes for the Treatment of Food Dyes: A Review

Otoniel Anacleto Estrela Filho,Naga Raju Maddela,Jennifer María Navia-Mendoza,Luis Angel Zambrano-Intriago,Joan Manuel Rodríguez-Díaz,Luis Santiago Quiroz-Fernández,Ricardo José Baquerizo-Crespo,Marta Maria Menezes Bezerra Duarte

doi:10.3390/su132111676

Abstract

The use of food additives (such as dyes, which improve the appearance of the products) has become more prominent, due to the rapid population growth and the increase in demand for beverages and processed foods. The dyes are usually found in effluents that are discharged into the environment without previous treatment; this promotes mass contamination and alters the aquatic environment. In recent years, advanced oxidation processes (AOPs) have proven to be effective technologies used for wastewater treatment through the destruction of the total organic content of toxic contaminants, including food dyes. Studies have shown that the introduction of catalysts in AOPs improve treatment efficiency (i.e., complete decomposition without secondary contamination). The present review offers a quick reference for researchers, regarding the treatment of wastewater containing food dyes and the different types of AOPs, with different catalyst and nanocatalyst materials obtained from traditional and green chemical syntheses.

Highlights

Introduction published maps and institutional affilFood dyes are used worldwide and are classified as natural, semi-synthetic, and synthetic [1]
Semiconductor-mediated photocatalysis of metal oxides (TiO2, ZnO, WO3, cadmium sulfide (CdS)) presents several limitations, including the difficulty to immobilize powder nanoparticles on substrates acting as support, rapid recombination of photoinduced electron-hole pairs, low activity in the visible region, toxicity to biological systems, and difficulty in enhancing photocatalytic activity
The present review demonstrates that advanced oxidation processes (AOPs) have great potential in the degradation treatment of food dyes since AOP chemistry offers several mechanisms for the treatment of this type of organic pollutant

Summary

Introduction

Introduction published maps and institutional affilFood dyes are used worldwide and are classified as natural, semi-synthetic, and synthetic [1]. There are more than 100,000 commercial dyes available, of which approximately 10–15% of the dyes usually enter the environment through industrial effluents without prior treatment [4] When these effluents are mixed with clean water they can unbalance the recommended level of organic and inorganic parameters in water bodies [5], impeding the processes of self-purification and biological degradation due to limited light transmittance [6]. Due to their recalcitrant nature, xenobiotic, highly toxic, and carcinogenic properties, they end up affecting the health of people and ecosystems in general [1,2,7,8,9,10]

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Conclusion