Bacterial immobilization in an SA/PVA/AC biocomposite matrix for enhanced biodegradation of Methyl Orange dye

Methyl Orange (MO) is particularly problematic due to its structural characteristics, which include a strong azo bond (–N=N–) that renders it resistant to conventional degradation methods. Its presence in wastewater can interfere with light penetration in aquatic environments, affecting photosynthesis and the overall health of aquatic organisms. This study evaluates the dye removal performance of free and immobilized bacteria (Pseudomonas aeruginosa, Bacillus subtilis, and Ralstonia pickettii) using an SA/PVA/AC (sodium alginate/polyvinyl alcohol/activated carbon) hydrogel matrix for Methyl Orange (MO) decolorization. The synthesized biocomposite was analyzed using Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX) to confirm the successful incorporation of bacteria while maintaining the matrix's functional integrity. The biocomposite demonstrated significant MO decolorization, with live immobilized R. pickettii achieving an 87.12% removal rate, outperforming both the matrix alone 35.60% and free bacterial cells (13.87%). Viability assessments indicated that the immobilization matrix was capable of maintaining bacterial activity during the experimental period. However, reusability studies revealed a noticeable decline in removal efficiency over successive cycles. This reduction may be related to factors such as nutrient depletion, accumulation of inhibitory metabolites, or structural changes in the matrix, although these effects were not specifically investigated in this study. Overall, the results suggest that bacterial immobilization using an SA/PVA/AC matrix represents a potentially useful and environmentally friendly strategy for dye removal. Future work should focus on systematic matrix optimization, detailed adsorption characterization, and long-term stability evaluation to improve durability and operational performance for practical applications.