Enhanced Transport of Zerovalent Iron Nanoparticles and Nitrate Removal in Saturated Porous Media

Zero-valent iron nanoparticles (ZVINs) as a new environment remediation technology has significant potential for the treatment of contaminated soil and groundwater. In spite of the high efficiency of ZVINs in the removal of various pollutants from porous media, their have some weaknesses such as lack of stability and a strong tendency to rapidly aggregate which limits their application in field scales. The main objectives of this study was to investigate the efficency of guar gum (GG), polyacrylamide (PAM), polystyrene sulfonate (PSS), polyvinylpyrrolidone (PVP) stabilized-ZVINs (GG-ZVINs, PAM-ZVINs, PSS-ZVINs and PVP-ZVINs) and non-stabilized (bare) ZVINs (Bare-ZVINs) on nitrate removal from sand-packed columns. The characteristics of the synthesized ZVINs were characterized by scanning and transmission electron microscopy (SEM, TEM), zeta-potential analyzer and X-ray diffraction (XRD) techniques. A series of transport experimaent on sand-packed column were conducted under different concentrations of ZVINs (1, 2, and 3 g/L) and initial nitrate concentration (150, 250, and 350 mg/L). The CXTFIT code was used to simulate nitrate reduction in the sand columns; and estimating the transport parameters. The results revealed that mechanisms such as straining, ripening and aggregation had a considerable impact on the ZVINs transport in porous media. The results indicated that by increasing nitrate concentration the removal efficiency was decreased and in contrast by increasing concentrations of the ZVINs the nitrate reduction potential showed an enhancing trend. The results also revealed that ZVINs had a potential for nitrate removal from sand columns upon the following order: PAM-ZVINs > GG-ZVINs > PSS- ZVINs > PVP- ZVINs > Bare- ZVINs.