Hematite nanoparticle modified granular activated carbon for removal of arsenic and organic co-contaminants

The goal of this study was to determine whether hematite nanoparticles could be synthesized within the pores of granular activated carbon (GAC) media by hydrolysis of ferric salt to effectively remove arsenic and organic co-contaminant from water. Five task-oriented objectives were undertaken to address this goal: (1) hematite modified GAC media was fabricated; (2) properties of the fabricated media were characterized; (3) arsenic adsorption capacity was evaluated under batch pseudo-equilibrium conditions in different water matrices; (4) adsorption capacity of the fabricated media was evaluated for model organic co-contaminant (methylene blue) under batch pseudo-equilibrium conditions; and (5) short bed column tests were conducted to estimate adsorption capacity under continuous flow conditions. Four different hybrid media were fabricated characterized with iron contents ranging from 0.9% to 4.4% of Fe per dry weight. Longer hydrolysis times in solutions with lower concentrations of ferric salt allow for higher iron content, better distribution of the nanoparticles and formation of pore volume in the macropore region. Characterized by the low Freundlich intensity parameters (1/n <1), the hybrid media with highest iron content exhibited better arsenic adsorption capacity and selectivity in waters with low arsenic concentrations than their counterparts. The introduction of nanoparticles within the pores of the granular activated reduced the adsorption capacity of the hybrid media for the model organic co-contaminant (methylene blue), but it did not affect the energy of adsorption.