Poly(acrylo-amidino ethylene amine) (PAEA) nanofiber membranes have been synthesized by combining the electrospinning technique and subsequent chemical modification. The membranes were used to remove As(V) from aqueous solution. The adsorption kinetics, equilibrium isotherms, and pH effect were investigated in batch experiments. The Langmuir isotherm and pseudo second-order kinetic models agree well with the experimental data. The PAEA nanofibers are effective for As(V) adsorption at pH 3. Experimental results showed that the maximum adsorption capacity of the PAEA nanofibers with As(V) is 76.92 mg g-1 , which is much higher than that of the PAEA microfibers (27.62 mg g-1 ). The adsorption rate of PAEA nanofibers is faster than that of PAEA microfibers due to its higher specific surface area. The PAEA nanofibers can be used as an effective adsorbent for the removal of As(V) in aqueous solution due to high adsorption capacity and short adsorption time to achieve equilibrium.
Porous chitosan(CS)/magnetic(Fe3O4 )/ferric hydroxide(Fe(OH)3 ) microsphere as novel and low-cost adsorbents for the removal of As(Ⅲ) have been synthesized via the electrospraying technology by a simple process of two steps. Characterization of the obtained adsorbents was studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The adsorption kinetics and equilibrium isotherms were investigated in batch experiments. The Langmuir, Freundlich isotherm and pseudo-second order kinetic models agree well with the experimental data. The adsorption of As(Ⅲ) onto CS/Fe3O4 /Fe(OH)3 microspheres occurred rapidly and reached adsorption equilibrium after about 45 min. The maximum adsorption capacity of CS/Fe3O4 /Fe(OH)3 microspheres, calculated by the Langmuir isotherm model, was 8.47 mg g-1 , which is higher than that of CS/Fe3O4 /Fe(OH) 3 prepared by the conventional method (4.72 mg g-1 ). The results showed that the microspheres had a high adsorption capacity for As(Ⅲ) and a high separation efficiency due to their microporous structure and superparamagnetic characteristics. Present research may eventually lead to a simple and low cost method for fabricating microporous materials and application for removal of arsenic from aqueous solution.
Thermal behavior and phase behavior in blends of liquid crystalline poly(aryl ether ketone) with lateral methoxy groups (M-PAEK) and poly(aryl ether ether ketone) containing thioether units (S-PEEK) have been investigated by differential scanning calorimetry (DSC) and polarized light microscopy (PLM) techniques. The results indicate that the composition of the blends has great effect on the phase behavior and morphology. Thin films of pure M-PAEK and S-PEEK crystallized from the melts exhibit typical mosaic and spherulitic structures, respectively. For the blends with higher M-PAEK contents (> 50%), an unusual ring-banded spherulite with structural discontinuity is formed. The bright core and rings of the ring-banded spherulites under PLM are composed of M-PAEK phase, while the dark rings consist mainly of S-PEEK phase. For the 50:50 M-PAEK/S-PEEK blend, the ring-banded spherulites and S-PEEK spherulites coexist, which implies that a partial phase separation between the two components takes place in the melting state. In S-PEEK-rich blends, a volume-filled spherulite is produced. In addition, the effect of isothermal crystallization temperature on the phase behavior, especially the ring-banded spherulite formation in the blends, is discussed.
LI Ye1, CHEN Jian2, LIU XinCai1 & YANG DeCai2 1Alan G. MacDiarmid Institute, Jilin University, Changchun 130012, China 2State Key Laboratory of Polymer Physics and Chemistry
