Catalytic degradation of methylene blue by iron nanoparticles synthesized using Galinsoga parviflora, Conyza bonariensis and Bidens pilosa leaf extracts

Green synthesized metallic nanoparticles are environmentally friendly, bio-compatible, and highly stable. The aim of this study was to synthesize iron nanoparticles (FeNPs) from FeCl3 solution using aqueous leaf extracts of Galinsoga parviflora (Gp), Conyza bonariensis (Cb) and Bidens pilosa (Bp) and use them in degradation of methylene blue dye. The iron nanoparticles were characterized using UV–Vis spectrophotometer, FT-IR spectrophotometer, X-ray Fluorescence (EDXRF), X-ray diffractometer (XRD), and scanning electron microscope (SEM). Phytochemical screening for presence of secondary metabolites revealed presence of phenolics, phytosterols and flavonoids. The total phenolic and flavonoid content in Galinsoga parviflora, Conyza bonariensis and Bidens pilosa leaf extracts were 57.67 ± 1.27, 117.13 ± 0.03, 126.27 ± 0.013 mg Gallic Equivalent/g of Dry Weight (mg GAE/g DW) and 39.00 ± 0.56, 45.50 ± 0.59, 33.13 ± 0.81 mg Rutin Equivalent/g of Dry Weight (mg RE/g DW) respectively. The UV–Vis spectrum of FeCl3 had a shoulder at 320 nm, which disappeared upon addition of G. parviflora, C. bonariensis and B. pilosa extracts confirming formation of iron nanoparticles. Evaluation of iron content of the synthesized nanoparticles revealed that the iron content in G. parviflora, C. bonariensis and B. pilosa extracts was 51, 47 and 44% respectively. XRD data revealed presence of a large amorphous coating that masked iron peaks, though 2 theta values observed have been reported to be of iron oxides. Methylene blue degradation studies revealed that CbNPs, BpNPs and GpNPs synthesized were good biocatalysts as they degraded the dye by 86, 84.3 and 92% respectively. Therefore, green synthesized iron nanoparticles is cost effective and environmentally safe in providing insight in the environmental removal of dyes.