Water contamination by arsenic (As) and selenium (Se) poses a serious threat to human health due to their high degree of toxicity and bioavailability. The present study examines the remediation of these toxic species from water through adsorption and/or photochemical transformation by using magnetite (Fe3O4) nanoparticles coated with a thin film of natural organic matter (NOM-MNP). The synthesized NOM-MNP was characterized by Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The high surface area and strong magnetic properties made the nanoparticles attractive because of fast adsorption and easy separation. For As(V) of 200 ppb, more than 98% adsorption completed in less than 30 minutes while a slower adsorption rate was observed for As(III) with the same NOM-MNP. The generation of reactive oxygen species (ROS) by this NOM-MNP under solar irradiation enabled us to transform the highly toxic As(III) to its less toxic form of As(V) with greater removal efficiency employing the adsorption and photochemical properties of the NOM-MNP. The adsorption process for the targeted As species was found to be in good agreement with pseudo-second order kinetics and followed the Freundlich isotherm model. The influence of solution pH was negligible at a wide range from 3-9 and thus implied the formation of inner sphere surface complexes between the nanoparticles and the poisonous As oxyanions. Investigation of co-existing ions effect revealed phosphate [and carbonate for As(V)] as the biggest competitor(s) of As species for the adsorption sites. Strong adsorption was also observed for the two selenium species, Se(IV) and Se(VI), where equilibrium was attained in less than 1 and 5 minutes respectively. Detailed adsorption and photoconversion studies for both As and Se species demonstrated the strong potential of this nanoadsorbent for real life application in the water treatment processes.

Application of natural organic matter coated magnetic iron oxide nanoparticles for the remediation of arsenic and selenium

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.