Microalgal-Mediated Synthesis of Fe3O₄/ZnO Nanocomposites using Chlorella vulgaris for Photodegradation of Dyes in Wastewater

Abstract

Abstract

Aquatic ecosystems and human health are severely threatened by the increasing amount of synthetic dye contamination in water bodies, necessitating the development of effective and environmentally friendly remediation techniques. In this study, the green synthesis of Fe₃O₄/ZnO nanocomposites was employed, assisted by microalgae, using biomass from Chlorella vulgaris as a biogenic stabilising and reducing agent. The effective fabrication of spherical, crystalline Fe₃O₄/ZnO nanoparticles with an average particle size of 32.5 nm was confirmed by characterisation of the biosynthesised nanocomposites using XRD, SEM, EDX, FTIR, and UV–Vis spectroscopy. Chlorella vulgaris was added to help develop a bio-functionalized surface that increased photocatalytic activity when exposed to visible light. Under simulated solar light, the photocatalytic performance of Fe₃O₄/ZnO nanocomposites was assessed against model dye pollutants, Congo red (CR) and methylene blue (MB). Within 120 minutes, the results showed notable degradation efficiencies of 98.3% for MB and 96.7% for CR. A pseudo-first-order model was used for kinetic analysis, and the rate constants for MB and CR were 0.0264 and 0.0218 min⁻¹ respectively. Furthermore, the magnetic characteristics that FeO₄ imparted made it simple to recover and reuse the nanocomposites for up to six cycles with no activity loss. The application of green nanotechnology in environmental remediation is advanced by this study, which shows the potential of Chlorella vulgaris-mediated synthesis as a sustainable method for synthesising high-performance Fe₃O₄/ZnO nanocomposites for the efficient treatment of wastewater contaminated with dyes.