Molecular characterization and green synthesis of iron oxide nanoparticles from Ureibacillus chungkukjangi for methylene blue degradation

Abstract

Synthetic dyes, such as methylene blue (MB), are increasingly becoming sources of water pollution and require better treatment strategies. This study describes an eco-friendly method for methylene blue degradation using green synthesized iron oxide nanoparticles form Ureibacillus chungkukjangi. This bacterium was isolated from clinical samples and identified using 16S rRNA gene amplification and sequenced using Sanger sequencing technology. The identified Ureibacillus chungkukjangi was submitted to NCBI with NCBI accession no. PQ568249.1. The secondary metabolites of the bacteria acted as capping agents to both reduce and stabilize the nanoparticle synthesis. The nanoparticle synthesis was achieved by the addition of iron chloride solution as a precursor to bacterial metabolites, forming the orange-brown solution to dark brown that showed initial signs of nanoparticle synthesis that were verified with UV–Vis Absorption spectra giving peaks at 380 nm. In FTIR spectra of the range examined (570–630 cm⁻¹), Fe–O bonds were observed, which confirms that biofunctionalization of the surface had been done. Also observed were O–H, C–H, C=O, and C–O functional groups of surfaces biofunctionalization. Furthermore, SEM analysis showed the particle size ranging from 50 to 400 nm while massively polygonal, where EDX analysis further confirmed the presence of iron in the sample. The degradation studies conducted over 15 days showed that there was a total of 89% methylene blue degradation at a nanoparticle-to-dye ratio of 1:1. In contrast, the ratio of 1:5 only yielded a 79% degradation. Furthermore, the Fe₃O₄ NPs were shown to have powerful antioxidant activity (scavenging up to 93.2%), as well as inflammatory activity (82.3% inhibition), anti-hemolytic activity (84.4% inhibition), which suggests low toxicity and biocompatibility. This confirms the effectiveness of biosynthesized Fe₃O₄ NPs for the treatment of dye-contaminated water, utilizing them as a cost-effective and multifunctional approach, thus advancing the field of nano bioremediation.