Photocatalytic Degradation of Methyl Violet and Auramine-O Dyes Using Ni/ZnO Nanocomposites for An Environmental Solution for Dye Wastewater

Adnan¹, Ajmal Shah², Talha Sharif², Muhammad Mjid Khan¹, Zain ul Abidin¹, Muhammad Sohail¹, Farah Muhammad Zada¹, Naseer Khan³,Fawad Ali⁴*,Saba Zafar^{5, 6}*

This study demonstrated Ni/ZnO photocatalysts as efficient, sustainable agents for degrading toxic dyes in wastewater, minimizing environmental impacts.

Abstract

Background: The increasing release of synthetic dyes, such as methyl violet (MV2B) and auramine O (AO), into water bodies from industrial effluents poses significant environmental and health risks due to their toxicity and persistence. Conventional wastewater treatment methods often fail to fully eliminate these dyes, leading to a demand for advanced techniques like photocatalysis. This study examines the efficacy of Ni-doped ZnO (Ni/ZnO) photocatalysts for the photodegradation of MV2B and AO dyes under UV irradiation. Methods: Ni/ZnO catalysts were synthesized via wet impregnation, followed by calcination and characterization through SEM, EDX, and XRD to confirm morphology, elemental composition, and structural changes. Photodegradation experiments were conducted with various dye concentrations, catalyst dosages, and irradiation times under controlled pH. The removal efficiency was assessed by measuring absorption changes pre- and post-degradation. Results: The optimized conditions showed significant degradation efficiencies of 86.36% and 69.31% for MV2B and AO, respectively. The study revealed that increasing catalyst dosage enhanced degradation by providing more active sites, while degradation efficiency decreased at higher dye concentrations due to competition for these sites. Kinetic analysis demonstrated that MV2B degradation followed a pseudo-second-order model, whereas AO conformed to a pseudo-first-order kinetic model. Conclusion: The Ni/ZnO photocatalyst proved highly effective in degrading MV2B and AO dyes, with pH optimization further improving performance. This research supports Ni/ZnO photocatalysis as a promising approach for treating dye-contaminated wastewater, contributing to sustainable environmental remediation efforts.

Keywords: Dye pollution, photocatalysis, Ni/ZnO, methyl violet, Auramine-O

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