Wei-Hong Xu

Enhanced arsenic removal from water by hierarchically porous CeO2–ZrO2 nanospheres: Role of surface- and structure-dependent properties

Arsenic contaminated natural water is commonly used as drinking water source in some districts of Asia. To meet the increasingly strict drinking water standards, exploration of efficient arsenic removal methods is highly desired. In this study, hierarchically porous CeO₂-ZrO₂ nanospheres were synthesized, and their suitability as arsenic sorbents was examined. The CeO₂-ZrO₂ hollow nanospheres showed an adsorption capacity of 27.1 and 9.2 mg g(-1) for As(V) and As(III), respectively, at an equilibrium arsenic concentration of 0.01 mg L(-1) (the standard for drinking water) under neutral conditions, indicating a high arsenic removal performance of the adsorbent at low arsenic concentrations. Such a great arsenic adsorption capacity was attributed to the high surface hydroxyl density and presence of hierarchically porous network in the hollow nanospheres. The analysis of Fourier transformed infrared spectra and X-ray photoelectron spectroscopy demonstrated that the adsorption of arsenic on the CeO₂-ZrO₂ nanospheres was completed through the formation of a surface complex by substituting hydroxyl with arsenic species. In addition, the CeO₂-ZrO₂ nanospheres were able to remove over 97% arsenic in real underground water with initial arsenic concentration of 0.376 mg L(-1) to meet the guideline limit of arsenic in drinking water regulated by the World Health Organization without any pre-treatment and/or pH adjustment.

Stable organic-inorganic hybrid of polyaniline/α-zirconium phosphate for efficient removal of organic pollutants in water environment.

In this article, organic-inorganic hybrid materials of polyaniline/α-zirconium phosphate (PANI/α-ZrP) was synthesized by in situ oxidative polymerization reaction and characterized by Fourier transformed infrared (FTIR), field-emission scanning electron microscopic (FE-SEM) and X-ray diffraction (XRD). The results showed that polyaniline (PANI) was successfully grown on the surface of α-zirconium phosphate (α-ZrP) nanoplates. The PANI/α-ZrP nanocomposites were further applied to remove methyl orange (MO), which was used as a model of organic pollutants in aqueous solution. A synergistic effect of PANI and α-ZrP on promoting the adsorption removal of MO was observed. The PANI/α-ZrP nanocomposites exhibited excellent maximum adsorption capacity toward MO (377.46 mg g(-1)), which is superior to that of PANI nanotubes (254.15 mg g(-1)) and much higher than that of many other adsorbents. The adsorption isotherms of MO can be well-fitted with the Langmuir model and the adsorption kinetics follows the pseudo-second-order model. MO adsorption decreased with increasing solution pH at pH > 4.0 implying that MO adsorption on PANI/α-ZrP may via electrostatic interactions between amine and imine groups on the surface of PANI/α-ZrP and MO molecules. This study implies that the hybrid materials of PANI/α-ZrP can be suggested as potential adsorbents to remove organic dyes from large volumes of aqueous solutions.

Ultra high adsorption capacity of fried egg jellyfish-like γ-AlOOH(Boehmite)@SiO2/Fe3O4 porous magnetic microspheres for aqueous Pb(II) removal

Fried egg jellyfish-like γ-AlOOH(Boehmite)@SiO2/Fe3O4 porous magnetic microspheres were synthesized by a simple template-induced method. The products were characterized by X-ray diffraction (XRD) analysis , scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption–desorption techniques and vibrating sample magnetometry (VSM). Influencing factors, such as the concentration of reactants, the reaction temperature and the reaction time, were systematically investigated. The adsorption properties of the fabricated sample were investigated for aqueous Pb(II) removal. The maximum adsorption capacity (qm) increased rapidly with an increasing void space in the shell of the microspheres, indicating that the void space is beneficial for increasing the adsorption properties of the material. The maximum adsorption capacity, qm = 214.59 mg g−1, is approximately 11.7-fold and 34.6-fold higher than SiO2/Fe3O4 and Fe3O4 magnetic microspheres, respectively. The adsorption isotherm fitted the Langmuir model well and the square of the correlation coefficient was r2 > 0.996. In addition, the effects of pH on the adsorption kinetics have also been investigated.

Self-assembled, monodispersed, flower-like γ-AlOOH hierarchical superstructures for efficient and fast removal of heavy metal ions from water

Self-assembled, monodispersed, uniform, and flower-like γ-AlOOH hierarchical superstructures have been synthesized in high yield via a simple, economical and environmentally friendly, hydrothermal route. The product possesses a large BET surface area of 145.5 m2 g−1. It is found that Pb(II) and Hg(II) ions can be quickly removed from aqueous solutions by the flower-like γ-AlOOH. After only 5 min, the removal rate for Pb(II) and Hg(II) ions is over 99.0%. The maximal adsorption is ca. 124.22 mg g−1 for Pb(II) and 131.23 mg g−1 for Hg(II).

Electrochemical and density functional theory investigation on high selectivity and sensitivity of exfoliated nano-zirconium phosphate toward lead(II).

A new strategy on the understanding of selective and sensitive identification of Pb(II) using combined experimental and theoretical efforts is described. Amorphous phase formation of exfoliated nano-zirconium phosphate (ZrP) has been prepared via a hydrothermal process and subsequent intercalation reaction. Exfoliated ZrP was used as coating on the electrode surface, and it was found to be selective and sensitive for Pb(II) detection due to its selective adsorption ability. To better and scientifically understand the microscopic adsorption mechanism, density functional theory (DFT) calculations about the details of chemical interactions between heavy metal ions and exfoliated ZrP were carried out at an atomistic level. It is verified that the exfoliated ZrP shows the strongest adsorption capability toward Pb(II) among all heavy metal ions, thereby resulting in selective detection consequently. With our combined experimental and theoretical efforts, we are able to provide a new route to realize the improved selectivity in electrochemical sensing of toxic metal ions.

Copper nanowires as nanoscale interconnects: their stability, electrical transport, and mechanical properties.

Application of copper nanowires (Cu NWs) for interconnects in future nanodevices must meet the following needs: environmental stability and superior electrical transport properties. Here, we demonstrate a kind of Cu NW that possesses the both properties. The Cu NWs were synthesized through a hydrothermal route with the reduction of copper chloride using octadecylamine (ODA). The reasons for their environmental stability could be due to interaction of ODA(+) molecules with the surface of Cu NWs and forming strong N-Cu chemical bonds. Electrical transport properties of individual Cu NW were investigated by using the four-probe measurement, showing the temperature-dependent resistance of the Cu NW was fairly linear in the temperature range from 25 to 300 K and the Cu NW retained the low resistivity of approximately 3.5 × 10(-6) Ω · cm at room temperature, near the resistivity value of bulk copper. The maximum transport current density for the Cu NW should be superior to 1.06 × 10(7) A · cm(-2). In addition, the Cu NWs have ultralow junction resistance. The present study indicates that the Cu NWs could act as a multifunctional building blocks for interconnects in future nanoscale devices.

Investigation of the facet-dependent performance of α-Fe2O3 nanocrystals for heavy metal determination by stripping voltammetry

We find for the first time that the electrochemical performances of the α-Fe2O3 nanostructures depend on their exposed facets. Density functional theory calculations are carried out to better and scientifically understand the effect of different exposed facets at the atomic-scale level.

Superparamagnetic mesoporous ferrite nanocrystal clusters for efficient removal of arsenite from water

Contaminated groundwater with a high concentration of arsenic continues to pose health threats to millions of people worldwide, especially in Asia. As(III) is the dominant arsenic species in groundwater, and is more toxic, soluble, and mobile than As(V). Affected communities need accessible technologies to remove As(III) from drinking water, especially in rural areas. In this study, a strategy is adopted to assemble small-sized magnetic MnFe2O4 nanocrystal building blocks to form mesoporous clusters (NCs) with the advantage of increasing the magnetization while retaining superparamagnetic characteristics by using a solvothermal method, which is beneficial for efficient separation from treated water by a moderate magnetic field. The MnFe2O4 NCs combined with uniform mesoporous structure and small constituent nanocrystals (about 8–12 nm in size) provides a synergistic effect for enhanced adsorption performance toward As(III) with an adsorption capacity (>27.27 mg g−1) under neutral conditions. The analysis of Fourier transformed infrared spectra and X-ray photoelectron spectroscopy demonstrates that the adsorption of As(III) on MnFe2O4 NCs is through the formation of a surface complex.

Conduction Performance of Individual Cu@C Coaxial Nanocable Connectors

Individual, ultralong Cu@C coaxial nanocables show excellent electrical transport properties in the temperature range of 5-350 K, and the room-temperature resistivity of the Cu nanowire core almost retains that of the bulk copper, indicating their potential application as connectors in micro- and nanodevices.

Performance and mechanism of hierarchically porous Ce–Zr oxide nanospheres encapsulated calcium alginate beads for fluoride removal from water

Hierarchically porous Ce–Zr oxide nanosphere encapsulated calcium alginate millimeter-sized beads (CZ-CABs) were synthesized by using a sol–gel templating technique. Their defluoridation performance, including static and dynamic adsorption, was systematically evaluated. The adsorption kinetic followed the pseudo-second-order model. The adsorption isotherm could be divided into two distinct regions depending on the fluoride concentrations, and the CZ-CABs exhibited a Langmuir–Freundlich maximum fluoride adsorption capacity of 137.6 mg g−1 under neutral conditions. Such a specific adsorption isotherm indicated that various mechanisms were involved in the fluoride adsorption depending on fluoride concentrations, which were further demonstrated by FTIR and XPS analyses. The effect of pH and co-existing anions on fluoride adsorption was studied. Furthermore, column adsorption experiments were conducted, and the results showed a high efficiency of the CZ-CABs for the removal of fluoride from water on a continuous flow basis.