Yong-Xing Zhang

Adsorption of Lead(II) on O2-Plasma-Oxidized Multiwalled Carbon Nanotubes: Thermodynamics, Kinetics, and Desorption

O(2)-plasma-oxidized multiwalled carbon nanotubes (po-MWCNTs) have been used as an adsorbent for adsorption of lead(II) in water. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy measurements show that the bulk properties of MWCNTs were not changed after O(2)-plasma oxidation. The adsorption capacity of MWCNTs for lead(II) was greatly enhanced after plasma oxidation mainly because of the introduction of oxygen-containing functional groups onto the surface of MWCNTs. The removal of lead(II) by po-MWCNTs occurs rather quickly, and the adsorption kinetics can be well described by the pseudo-second-order model. The adsorption isotherm of lead(II) onto MWCNTs fits the Langmuir isotherm model. The adsorption of lead(II) onto MWCNTs is strongly dependent upon the pH values. X-ray photoelectron spectroscopy analysis shows that the adsorption mechanism is mainly due to the chemical interaction between lead(II) and the surface functional groups of po-MWCNTs. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) calculated from the adsorption isotherms suggest that the adsorption of lead(II) onto MWCNTs is endothermic and spontaneous. The regeneration performance shows that lead(II) can be easily regenerated from po-MWCNTs by altering the pH values of the solution.

Three-dimensional hierarchical flower-like Mg–Al-layered double hydroxides: highly efficient adsorbents for As(V) and Cr(VI) removal

3D hierarchical flower-like Mg-Al-layered double hydroxides (Mg-Al-LDHs) were synthesized by a simple solvothermal method in a mixed solution of ethylene glycol (EG) and water. The formation mechanism of the flower-like Mg-Al-LDHs was proposed. After calcination, the flower-like morphology could be completely preserved. With relatively high specific surface areas, Mg-Al-LDHs and calcined Mg-Al-LDHs with 3D hierarchical nanostructures were tested for their application in water purification. When tested as adsorbents in As(V) and Cr(VI) removal, the as-prepared calcined Mg-Al-LDHs showed excellent performance, and the adsorption capacities of calcined Mg-Al-LDHs for As(V) and Cr(VI) were better than those of Mg-Al-LDHs. The adsorption isotherms, kinetics and mechanisms for As(V) and Cr(VI) onto calcined Mg-Al-LDHs were also investigated. The high uptake capability of the as-prepared novel 3D hierarchical calcined Mg-Al-LDHs make it a potentially attractive adsorbent in water purification. Also, this facile strategy may be extended to synthesize other LDHs with 3D hierarchical nanostructures, which may find many other applications due to their novel structural features.

High adsorptive γ-AlOOH(boehmite)@SiO2/Fe3O4 porous magnetic microspheres for detection of toxic metal ions in drinking water

γ-AlOOH(boehmite)@SiO(2)/Fe(3)O(4) porous magnetic microspheres with high adsorption capacity toward heavy metal ions were found to be useful for the simultaneous and selective electrochemical detection of five metal ions, such as ultratrace zinc(II), cadmium(II), lead(II), copper(II), and mercury(II), in drinking water.

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).

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.

An alternative hydrothermal route to amorphous carbon nanotubes for treatment of organic pollutants in water

Ultralong and uniform amorphous carbon nanotubes (ACNTs) were prepared by using a simple and environmental friendly hydrothermal method at low temperature. Factors affecting the growth of the ACNTs were systematically studied. A reasonable Ostwald ripening growth mechanism was proposed for the formation of the ACNTs. The as-prepared ACNTs were used as an adsorbent for the removal of methylene blue (MB) from aqueous solutions in two modes, batch and fixed bed. In the batch mode, the removal efficiency for MB was improved remarkably by increasing the contact time and the adsorbent dosage. High pH values were in favor of the adsorption for MB. The adsorption isotherm of the ACNTs was well fitted with Langmuir model, with square of correlation coefficient r2 > 0.9996. The maximum adsorption capacity (qm = 46.21 mg g−1) of the ACNTs was higher than that of the multi-walled carbon nanotubes (qm = 35.83 mg g−1). In addition, the adsorption kinetics results presented two adsorption stages. The rapid and the slow adsorption stages resulted from the adsorption of the external and the inner surface of the ACNTs, respectively. In the fixed-bed mode, the MB removal percentage increased with decreasing the flow rate and the concentration of MB. The results reveal that the as-prepared ACNTs can be employed as an adsorbent for the removal of organic pollutants from wastewater.