ABSTRACT
In this research, the layer-by-layer coating of silica sand surface with monolayer of graphene oxide (GO) immobilized on magnetite nanoparticles (Fe3 O4 MNPs) sublayer was investigated as a novel, low-cost, effective, and green nanocomposite material for adsorption of phenol and 2,4-dichloro-phenol (DCP). Several characterization techniques such as FTIR spectroscopy, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) were used to confirm the successful synthesis of Fe3 O4 MNPs@GO on silica. The efficiency of Fe3 O4 MNPs@GO-coated silica (SiO2 ) for the removal of the target phenolic compounds from water samples was evaluated. The maximum removal of phenol (52%) and DCP (73%) was observed using 1.0 g adsorbent, initial concentration of 12.5 mg/dm3 (for phenol) and 15 mg/dm3 (for DCP), sample volume of 10 ml (for phenol) and 15 ml (for DCP), contact time of 20 min (for phenol) and 10 min (for DCP), and pH = 5. The adsorption isotherm models of Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich as well as kinetic and intraparticle diffusion models were also examined. Eventually, SiO2 /Fe3 O4 MNPs@GO was regenerated five times for removal of examined contaminants and their removal efficiency from the water inlet of a water treatment plant was assessed. PRACTITIONER POINTS: Immobilizing monolayer of GO nanosheets on silica sands surface for the first time has been achieved. GO monolayer anchors on silica sands through Fe3 O4 nanoparticles as sublayer without using very expensive tris(hydroxymethyl) aminomethane agent. Modified silica sands are introduced as a novel and economic pollutants adsorbent, which can be used in filter sands of water treatment industry. The SiO2 /Fe3 O4 MNPs@GO significantly reduces the amount of phenol and 2,4-dichloro-phenol (DCP) as model organic pollutants from water samples.