Chiang Mai Journal of Science

The effects of calcination temperature on the magnetic characteristics of iron oxide magnetic nanoparticles (MNPs) for arsenic adsorption were explored in this study. The MNPs were synthesized by precipitation from a ferrous / ferric chloride solution, and a heat treatment at temperatures of 80-700°C. Magnetic characteristics, XRD and FTIR analyses indicate that the MNPs treated at 80°C were predominantly magnetite with less abundant goethite, while calcination at 200-500°C showed a magnetite/maghemite mixture, and hematite at 600-700°C. The crystallite sizes of the MNPs prepared at 350°C and 700°C were estimated at 18.5 and 27.6 nm, respectively. The highest As(III) adsorption capacity was 46 mg/g for the  MNPs calcined at 80°C, and decreased to 15 mg/g for the MNPs calcined at 700°C. The result indicates that heat treatment at 350°C is observed to be maximum for preparation of the MNPs with the As(III) adsorption capacity of more than 40 mg/g.