Transport of surface-modified iron nanoparticle in porous media and application to arsenic(III) remediation

The surface-modified iron nanoparticles (S-INP) were synthesized, characterized and tested for the remediation of arsenite (As(III)), a well known toxic groundwater contaminant of concern. The S-INP material was fully dispersed in the aqueous phase with a particle size distribution of 2–10 nm estimated from high-resolution transmission electron microscopy (HR-TEM). X-ray photoelectron spectroscopy (XPS) revealed that an Fe(III) oxide surface film was present on S-INP in addition to the bulk zero-valent Fe⁰ oxidation state. Transport of S-INP through porous media packed in 10 cm length column showed particle breakthroughs of 22.1, 47.4 and 60 pore volumes in glass beads, unbaked sand, and baked sand, respectively. Un-modified INP was immobile and aggregated on porous media surfaces in the column inlet area. Results using S-INP pretreated 10 cm sand-packed columns containing ∼2 g of S-INP showed that 100 % of As(III) was removed from influent solutions (flow rate 1.8 mL min⁻¹) containing 0.2, 0.5 and 1.0 mg L⁻¹ As(III) for 9, 7 and 4 days providing 23.3, 20.7 and 10.4 L of arsenic free water, respectively. In addition, it was found that 100% of As(III) in 0.5 mg/L solution (flow rate 1.8 mL min⁻¹) was removed by S-INP pretreated 50 cm sand packed column containing 12 g of S-INP for more than 2.5 months providing 194.4 L of arsenic free water. Field emission scanning electron microscopy (FE-SEM) showed S-INP had transformed to elongated, rod-like shaped corrosion product particles after reaction with As(III) in the presence of sand. These results suggest that S-INP has great potential to be used as a mobile, injectable reactive material for in-situ sandy groundwater aquifer treatment of As(III).     

Effect of gamma irradiation on polypropylene yarns under air and water

Journal of Radioanalytical and Nuclear Chemistry - Polypropylene (PP) filters are used for the treatment of radioactive liquid waste containing gamma nuclides such as Co-60, and filter physical and...     

Behaviors of Perfluorocarbon Emulsion during Dissolution of Oxide Layers

This study investigates the dissolution behavior of oxide layers containing radionuclides using perfluorocarbon (PFC) emulsion as a reusable medium. Chemicals such as PFC, anionic surfactant, and H₂SO₄ are used for preparing the PFC emulsion, and emulsified using an ultrasonication process. The FTIR results show O–H stretching that is formed by the interaction of the carboxyl group of the anionic surfactant with the hydroxyl group of water containing H₂SO₄, and find that the H₂SO₄ can be homogeneously dispersed in the PFC–anionic surfactant–H₂SO₄ emulsion. The dissolution test of the simulated Cr₂O₃ specimen is conducted using PFC emulsion containing KMnO₄. Through the weight losses of specimens and Scanning Electron Microscope-Energy Dispersive X-ray Spectrometer (SEM-EDS) analysis, it is confirmed that the Cr₂O₃ layer on the SUS304 specimen is easily dissolved using PFC emulsion. During the dissolution of the Cr₂O₃, it is observed that the dispersed H₂SO₄–KMnO₄ became unstable and separated from PFC emulsion. Based on these results, the behavior of the PFC emulsion during the dissolution of the oxide layer is explained.     

Nanostructured Sn/TiO2/C composite as a high-performance anode for Li-ion batteries

A nanostructured Sn/TiO₂/C composite was prepared from SnO, Ti, and carbon powders using a mechanochemical reduction method and evaluated as an anode material in rechargeable Li-ion batteries. The Sn/TiO₂/C nanocomposite was composed of uniformly dispersed nanocrystalline Sn and rutile TiO₂ in amorphous carbon matrix. In addition, electrochemical Li insertion/extraction in rutile TiO₂ was examined by ex situ XRD and extended X-ray absorption fine structure. The Sn/TiO₂/C nanocomposite exhibited excellent electrochemical performance, which highlights its potential as a new alternative anode material in Li-ion batteries.     

Effect of Fenton-like oxidation on enhanced oxidative degradation of para-chlorobenzoic acid by ultrasonic irradiation

Sonolysis, Fenton-like oxidation (FeOOH-H2O2), and a combination of the two processes were used to facilitate the degradation of para-chlorobenzoic acid (a model compound for free radical mediated reactions). The objective of this study was to investigate the effect of FeOOH and H2O2 dosages on the degradation of para-chlorobenzoic acid (p-CBA) using ultrasound/FeOOH-H2O2. The oxidation rate of p-CBA was measured at various concentrations of H2O2 and FeOOH particles and pH conditions. pH's below the pKa of p-CBA (3.98), showed significantly better degradation of p-CBA than at higher values from 5 to 9. The rates of degradation of p-CBA by FeOOH-H2O2 were enhanced in the presence of ultrasound. The first-order rate constant, k for p-CBA degradation by ultrasound was 4.5 x 10(-3) min(-1), and in the presence of FeOOH-H2O2 this was found to be substantially faster (1.54 x 10(-2) min(-1)). The observed rate enhancements for the degradation of p-CBA can be attributed primarily to the continuous cleaning and chemical activation of the FeOOH surfaces by acoustic cavitation and the accelerated mass transport rates of reactants and products between the solution phase and the FeOOH surface. This new process provides a viable alternative to existing oxidation technologies.     

As(V) remediation using electrochemically synthesized maghemite nanoparticles

Maghemite nanoparticles were electrochemically synthesized from environmentally benign solutions in ambient conditions and utilized to remediate As(V) from aqueous solution. The average size and surface area of the maghemite nanoparticles were controlled to be 11–23 nm and 41–49 m² g^?1, respectively, by adjusting applied current density. The point of zero charge and crystallinity were independent of size. The effect of size and environmental conditions (i.e., maghemite nanoparticles content, contact time, and solution pH) on the adsorption of As(V) were systematically investigated. Similar to As(V) remediation using zero valent iron nanoparticles (NZVI), the kinetics of adsorption were best described by the pseudo first order model where the remediation is limited by the mass transfer of As(V) to adsorption sites of maghemite. The adsorption was spontaneous and endothermic which fitted with the Langmuir and Freundlich isotherms. The results observed in batch study indicate that maghemite nanoparticles were suitable adsorbent for remediating As(V) concentration to the limit (10 μg l^?1) recommended by the World Health Organization (WHO).