No abstract

This study aims to remove perchlorate using single-walled carbon nanotubes (SWCNTs) or granular activated carbon (GAC). Dynamic and equilibrium adsorption experiments were performed to evaluate the thermodynamic behavior of perchlorate on SWCNTs and GAC. Key parameters affecting the adsorption, such as pH, ionic strength, and temperature were studied. The experimental results showed that the dynamic adsorption experiment achieved equilibrium in approximately eight hours. The adsorption capacity increased as the concentration of perchlorate increased or as the ionic strength decreased. The selected adsorption models were the modified Freundlich, the pseudo-1st-order, and the pseudo-2nd-order equations. The results showed that the modified Freundlich equation best described the kinetic adsorption processes. The maximal adsorption capacities of GAC and SWCNTs were 33.87-28.21 mg/g and 13.64 - 10.03 mg/g, respectively, at a constant temperature between 5°C and 45°C. The thermodynamic parameters, such as the equilibrium constant (K0 ), the standard free energy changes (ΔG°), the standard enthalpy change (ΔH°) and the standard entropy change (ΔS°), were obtained. The results of the isothermal equilibrium adsorption experiment showed that low pH levels, low ionic strength, and low-temperature conditions facilitated the perchlorate adsorption, indicating that GAC and SWCNTs are potential absorbents for water treatment.

Because of the expected long spin-transport length of organic materials, the magnetic metal/organic interface is crucial to the application of organic spintronics. In this study, [Fe/C 60 ] 3 multilayers were fabricated for the investigation of C 60 -mediated magnetic interlayer coupling. [Fe/C 60 ] 3 thin films were characterized using the magneto-optical Kerr effect, transmission electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS). The thin films revealed in-plane magnetic anisotropy, and the magnetic coercivity (H c ) drastically decreased from 6-8 mT to 0.5 mT with the increase of C 60 thickness from 0.1 nm to 5 nm. The insertion of the C 60 layer considerably reduced H c because a thickness greater than 1 nm of the C 60 layer is sufficient for blocking magnetic exchange coupling between Fe layers. In addition, post-annealing increased H c because of Fe inter-diffusion, which promotes magnetic exchange coupling and further Fe-C bonding, as confirmed by a comparative study of XPS C-spectra. The thermally triggered inter-diffusion between Fe and C 60 layers turned the multilayers into a mixed composite film and thus caused magnetic variation. Annealing time and temperature can be used as control parameters for the tuning of magnetism in Fe-C 60 composites.