| Summary: | The research studied the bacterial synthesis of magnetic iron oxide nanoparticles (FeNPs), their biological activity, and the biodegradation efficiency of Acid Red 88. An iron-resistant bacterial strain S2 was isolated from Choghart iron mine soil and selected to synthesize FeNPs. The phylogenetic analysis depended on 16S rDNA sequence comparison resolution and showed that strain S2 was 99.68% similar to Bacillus zhangzhouensis. FeNPs were identified by UV–Vis, FTIR, and XRD spectroscopy. SEM-EDX conclusions corroborated the size of FeNPs in the range of 20–70 nm in the rhombus form. The finding indicated that FeNPs had antimicrobial activity on tested bacteria. According to the brine shrimp lethality (BSL) test, FeNPs showed great anticancer activity with LC50 value of 0.5 μg/ml. The biodegradation of Acid Red 88 was investigated separately by FeNPs/Ca-Alg beads and FeNPs powder. FeNPs/Ca-Alg beads decolorized Acid Red 88 with 100% efficiency after 24 h, while FeNPs powder decolorized Acid Red 88 with 100% efficiency after 72 h. Moreover, Ca-Alg beads were applied as control and could not decolorize the dye. Decolorization of Acid Red 88 using FeNPs/Ca-Alg beads was investigated by GC/MS analysis. In this analysis, no mass was found related to the initial mass of Acid Red 88. According to these conclusions, it can be inferred that the dye is completely decomposed. The toxicity of Acid Red 88 dye, and the decolorization products, was assessed using BSL and phytotoxicity test. The conclusions determined that Acid Red 88 dye had toxicity effect. Further, the decolorization products could not kill half of the shrimp due to their low toxicity and did not inhibit the germination of radish seeds.
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