Sustainable biodegradation of reactive blue 222 dye: A study on bacterial immobilization and process optimization
2025
Walaa S. Mohamed
The textile industry is one of the biggest water-consuming industries in the world. It was the leading water-discharging industry and contributed to much of the world’s water pollution because most of the reactive dyes, such as reactive blue 222, harm aquatic systems and human health. Thus, the study aimed to evaluate the ability of immobilized Aeromonas hydrophila to decolorize the dye under aqueous conditions. The wastewater samples were spiked with the dye, and the isolates of the bacterial strain were immobilized on sodium alginate beads. For the optimization of the decolorization process concerning bead dosage, contact time, pH, and dye concentration, the Response Surface Methodology (RSM) technique was applied. The immobilized system achieved up to 98.54% decolorization efficiency under optimal conditions. Ultraviolet-visible spectroscopy, Fourier Transform Infrared Spectroscopy, and Gas Chromatography-Mass Spectrometry analyses confirmed dye degradation through azo bond cleavage, aromatic ring breakdown, and the formation of intermediate metabolites such as aromatic amines, phenolic compounds, and carboxylic acids. These transformations indicated progressive detoxification and mineralization of the dye into environmentally benign end products. Importantly, the immobilized strain maintained effective performance over multiple reuse cycles, highlighting its operational stability. This study is the first to demonstrate the application of immobilized A. hydrophila for Reactive Blue 222 degradation, providing a sustainable, reusable, and cost-effective strategy for textile wastewater treatment.
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