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Bacillus sp. Tol1-mdiated Decolorization and Synthesis of EPS-Stabilized Biogenic Silver Nanoparticle for Photocatalytic Removal of Disperse Red 1
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DOI：10.3390/catal16080721.png)
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Abstract
En 中文
Synthetic azo dyes are the largest class of industrial colorants having widespread application in textile, food, cosmetic, and pharmaceutical industries. Moreover, they are persistent and toxic, threatening aquatic environments as well as human health. Disperse red 1 (DR1), a mono-azo dye belonging to the disperse dye group and widely used in polyester dyeing, cosmetics, and other applications, is of particular concern due to its mutagenic potential and resistance to conventional treatment processes. The present study investigated an integrated DR1 removal strategy using thermotolerant Bacillus licheniformis Tol1 as well as its EPS-stabilized biogenic silver nanoparticles (AgNPs). With a maximum tolerable concentration of 0.5 g L−1, B. licheniformis Tol1 showed a maximum decolorization of 70.86% (0.2 g L−1, 55 °C). However, response surface methodology (RSM) based on the Box–Behnken design showed an actual decolorization efficiency of 73.13%. The artificial neural network (ANN) model predicted an accuracy of R2 = 0.9933, confirming the robustness and reliability of the experimental findings. To enhance dye removal efficiency, Tol1 EPS-stabilized AgNPs were synthesized via a green method and characterized using UV-Vis, SEM-EDAX, TEM, AFM, FTIR, DLS and zeta potential. Characterization of AgNP confirmed the formation of spherical stable AgNPs with an average size of 19.99 ± 0.38 nm, indicating polydisperse colloids nature with moderate electrostatic stability. A sunlight/H2O2-assisted process (photocatalytic experiments) demonstrated DR1 decolorization (80.72 ± 1.72% within 5 h under sunlight) following pseudo-first-order kinetics (k = 0.271 h−1). Furthermore, FTIR analysis confirmed the degradation of the chemical structure of DR1 through the disappearance of the characteristic azo (–N=N–) bond, indicating cleavage of the dye molecule. Overall, the present study provides a dual biological–nanotechnological approach for DR1 decolorization using single bacteria as well as its polysaccharide-stabilized AgNP, a sustainable eco-friendly future approach. However, further studies on complete mineralization, transformation products, toxicity evaluation, detailed catalyst reusability, and silver (Ag) leaching are needed to facilitate the practical implementation for wastewater treatment.
Keywords:
EPS-stabilized AgNPs
azo dye decolorization
disperse red 1 (DR1)
sunlight/H<sub>2</sub>O<sub>2</sub>-assisted process (photocatalysis)
ANN modeling
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