Iron oxide nanoparticles derived from Chlorella vulgaris extract: Characterization and crystal violet photodegradation studies

Nanoparticles were first used a century ago, but have recently gained popularity due to their ease of use, eco-friendliness, pollution-free nature, nontoxicity and low cost for wastewater treatment applications. In terms of nanoparticles preparation, green synthesis is a more convenient, economical, quick, and environmentally friendly process than traditional synthesis (i.e. chemical and mechanical) methods. The objective of this study was to synthesise iron oxide nanoparticles from iron (III) chloride using microalgae (Chlorella vulgaris) extract for photodegradation of crystal violet (CV) dye. Various characterization methods such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier-transform infrared spectroscopy (FTIR) were used to examine properties of the nanoparticles including its crystallinity, morphologies and sizes, and functional groups, respectively. The CV photodegradation process was carried out under different process conditions included initial CV concentration (10 mg/L – 25 mg/L), CV solution pH (5.39 – 8.98), and irradiation period (30 – 90 mins) to investigate the optimum operating conditions for the CV removal. The analysis using FESEM demonstrated that the nanoparticles exhibited irregularities and cylindrical shapes, measuring 109 nm in size. Meanwhile, the XRD analysis indicated that the iron oxide nanoparticles possessed a tetragonal crystal structure. The presence of Fe-O stretching vibrations at 486 cm-1 was confirmed by the FTIR spectrum. In terms of CV photodegradation studies, the optimum operating conditions for CV removal using iron oxide nanoparticles were determined to be at initial CV concentration of 10 mg/L, solution pH of 8.98, and an irradiation period of 90 mins, with a percentage removal of 96.21 %.