Enhanced Effluent Degradation with Zinc Oxide, Carbon Nitride, and Carbon Xerogel Trifecta on brass monoliths

Abstract

In recent years, heterogeneous photocatalysis has emerged as an alternative for the treatment of organic pollutants. This technique presents advantages such as low cost and ease of operation. However, finding a semiconductor material with operational viability and high activity under solar irradiation is a challenge, almost always in nanometric sizes. Furthermore, in many processes, the photocatalysts are suspended in the solution, which means that additional steps are required to remove them, which can make the technique economically unviable, especially when the catalysts are in nanometric size. This work aims to demonstrate the feasibility of using structured photocatalyst (ZnO, g-C3N4, and carbon xerogel), optimized for this photodegradation process. The synthesized materials were characterized by nitrogen adsorption and desorption techniques, X-ray diffraction (XRD), and diffuse reflectance spectroscopy (DRS). Adhesion testing demonstrated the efficiency of the deposition technique, with film adhesion exceeding 90%. The photocatalytic evaluation was performed with a mixture of three textile dyes in a recycle photoreactor, varying pH (4.7 and 10), recycle flow rate (2, 4, and 6 L h− 1), immobilized mass (1, 2, and 3 mg cm− 2), monolith height (1.5, 3.0, and 4.5 cm), and type of radiation (solar and visible artificials; and natural solar). The structured photocatalyst was able to degrade over 99% of the dye mixture using artificial radiation. The results obtained using solar energy were highly promising, achieving a degradation efficiency of approximately 74%. Furthermore, it was possible to regenerate the structured photocatalyst up to seven consecutive times using exclusively natural solar light and maintain a degradation rate of around 70%. These results reinforce the feasibility and potential application of this system in photocatalytic reactions, highlighting its effectiveness and sustainability.