Degradation of Brill Red 10B Textile Dye: A Comparative Study of Coconut Husk Biochar Immobilized Bacteria and Eichhornia crassipes-Mediated Ag/ZnO Nanoparticles

Abstract

This study investigates the degradation of Brilliant Red 10B dye in textile wastewater using four sustainable treatment strategies: Bacillus subtilis-mediated biodegradation, coconut husk biochar adsorption, immobilized bacterial systems, and green-synthesized Ag/ZnO nanoparticles. Seven bacterial isolates were cultured from textile wastewater, characterized, and the BRDB 3 isolate achieved up to 75.2% dye degradation under optimized conditions. Biochar prepared from coconut husk by pyrolysis at 600 °C removed 100% of dye at low concentrations within one hour. Immobilized BRDB 3 and BRDB 4 resulted in 85.07% and 78.85% degradation, respectively. Ag/ZnO nanoparticles synthesized with Eichhornia crassipes extract exhibited rapid dye degradation, reaching 80% in 20 min under sunlight. CHB was the most effective adsorbent (91.6% removal) when used on real textile wastewater, followed by immobilized BRDB 3 (83.27%), and Ag/ZnO NPs had intermediate performance (32.11%). The GC–MS analysis showed that Ag/ZnO NPs acted as extensive molecular breakers, which generated a range of low-molecular-weight compounds. In contrast, Coconut husk biochar and immobilized bacterial treatments yielded high degradation rates but left some persistent high-molecular-weight residues. These findings indicate the moderately good catalytic performance of the Ag/ZnO nanoparticles and establish the importance of combining the biological and adsorptive frameworks to achieve effective textile wastewater purification.