Arsenic(V) removal from groundwater using nano scale zero-valent iron as a colloidal reactive barrier material.
The removal of As(V), one of the most poisonous groundwater pollutants, by synthetic nanoscale zero-valent iron (NZVI) was studied. Batch experiments were performed to investigate the influence of pH, adsorption kinetics, sorption mechanism, and anionic effects. Field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Mossbauer spectroscopy were used to characterize the particle size, surface morphology, and corrosion layer formation on pristine NZVI and As(V)-treated NZVI. The HR-TEM study of pristine NZVI showed a core-shell-like structure, where more than 90% of the nanoparticles were under 30 nm in diameter. Mössbauer spectroscopy further confirmed its structure in which 19% were in zero-valent state with a coat of 81% iron oxides. The XRD results showed that As(V)-treated NZVI was gradually converted into magnetite/maghemite corrosion products over 90 days. The XPS study confirmed that 25% As(V) was reduced to As(III) by NZVI after 90 days. As(V) adsorption kinetics were rapid and occurred within minutes following a pseudo-first-order rate expression with observed reaction rate constants (Kobs) of 0.02-0.71 min(-1) at various NZVI concentrations. Laser light scattering analysis confirmed that NZVI-As(V) forms an inner-sphere surface complexation. The effects of competing anions revealed that HCO3-, H4SiO4(0), and H2PO4(2-) are potential interfering agents in the As(V) adsorption reaction. Our results suggest that NZVI is a suitable candidate for As(V) remediation.
Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, Korea.
Sushil Raj
SR
Kanel
Jean-Mark
JM
Greneche
Heechul
H
Choi
D000327:Adsorption; D001151:Arsenic / Q000737:chemistry / Q000302:isolation & purification*; D001639:Bicarbonates / Q000737:chemistry; D003102:Colloids / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry / Q000494:pharmacology*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology; D010316:Particle Size; D010710:Phosphates / Q000737:chemistry; D012824:Silicic Acid / Q000737:chemistry; D014877:Water Pollution, Chemical / Q000517:prevention & control; D018508:Water Purification / Q000379:methods*; D014881:Water Supply; D014961:X-Ray Diffraction
D001639:Bicarbonates; D003102:Colloids; D010710:Phosphates; D012824:Silicic Acid; D007501:Iron; D001151:Arsenic