Shiquan Liu

Influence of Surfactant Concentration on the Surface Morphology of Hollow Silica Microspheres and Its Explanation

The surface morphology of hollow silica microspheres has influence on their applications. After a thorough investigation of the deposition of silica nanoparticles on polystyrene (PS) beads and the surface morphology and texture of the resultant hollow silica shells with scanning electron microscopy, transmission electron microscopy, and N2-sorption measurements, the influence of surfactant [cetyltrimethylammonium bromide (CTAB)] concentration on the surface morphology of hollow silica microspheres templated by PS beads is explained. Previously, CTAB was believed to turn the surface charge of PS beads from negative into positive so that negatively charged silica could be deposited on the PS template. Here, we show CTA+ cations preferentially assemble with silica species to form silica-CTA+ composite nanoparticles. Since the zeta potential of silica-CTA+ composite nanoparticles is smaller than that of pure silica nanoparticles, these composite nanoparticles encounter less repulsion when they are deposited on the surface of PS beads and close to each other. As more CTAB is added, the silica-CTA+ nanoparticles are less negatively charged, and more compact and smooth hollow silica microspheres are obtained.

Preparation and Characterization of Activated Carbon Fiber from Paper

Activated carbon fibers (ACFS) with surface area of 1388 m2/g prepared from paper by chemical activation with KOH has been utilized as the adsorbent for the removal of methylene blue from aqueous solution. The experimental data were analyzed by Langmuir and Freundlich models of adsorption. The effects of pH value on the adsorption capacity of ACFS were also investigated. The rates of adsorption were found to conform to the kinetic model of Pseudo-second-order equation with high values of the correlation coefficients (R>0.998). The Langmuir isotherm was found to fit the experimental data better than the Feundlich isotherm over the whole concentration range. Maximum adsorption capacity of 520 mg/g at equilibrium was achieved. It was found that pH played a major role in the adsorption process, higher pH value favored the adsorption of MB.

Starch-assisted synthesis and photocatalytic activity of monosized cuprous oxide octahedron microcrystals

Abstract Octahedral cuprous oxide (Cu2O) crystals with different particle sizes were successfully synthesized by a simple starch-assisted method. The morphology and size of the obtained samples were examined by field-emission scanning electron microscopy and particle size analyzer. X-ray powder diffraction and ultraviolet–visible absorption spectra were also employed to characterize the crystallinity and light response. The photocatalytic activities of the as-prepared octahedral Cu2O have been investigated under ultraviolet light irradiation, and samples of different sizes exhibit excellent photocatalytic activity toward MO degradation. This simple one-pot synthetic route could provide a good starting point for the research of size-dependent catalytic properties of other materials.Graphical Abstract

Influence of Kaolin on the Sintering of Glass Powder to Glass–Ceramics

Abstract Glass powder derived from a waste water flocculate was used to prepare sintered glass–ceramics. Different amounts of kaolin as a binder were mixed with the glass powder to form green bodies. The influence of the kaolin on the sintering, crystallization of the glass powder and on the microstructure of the obtained glass–ceramics has been investigated. DTA analysis suggests that the kaolin increases the crystallization temperature of the glass-kaolin mixtures. The results also show that the kaolin benefits reducing the sintering shrinkage of the green bodies. The kaolin does not lead to the change of crystalline phases in the sintered glass–ceramics. Instead, with an appropriate addition, the kaolin can provide reactive Al2O3 and SiO2 sources due to its decomposition favoring the crystal growth and improving the mechanical property of the sintered product.

A novel high selectivity sensor for tetradifon residues based on double-side hollow molecularly imprinted materials

A sensitive and rapid technique for high selectivity detection of tetradifon has been developed. This method is based on a new kind of hollow shell molecularly imprinted (MI) polymer. In this method, the new hollow shell MI polymer has bigger specific surface areas compared with the traditional one based on the double-sides hollow microspheres structure. The proposed method has the advantage of wider linear range and lower limit of detection compared with the traditional one. The change in chemiluminescence (CL) intensity is linearly proportional with the concentration of tetradifon in the range 0.1∼12 μg mL−1 and the detection limit has reached 0.0483 μg mL−1. The new MI-CL sensor has been successfully applied to the determination of residual tetradifon in food and the results obtained compare well with those by other methods.

Influence of ammonia concentration on the formation of hollow silica microspheres via polystyrene beads templating

Abstract The influence of ammonia concentration on the formation of hollow silica microspheres via polystyrene beads templating was investigated. Hollow silica microspheres could only be templated in water – ethanol – ammonia – tetraethyl orthosilicate media with low concentrations of ammonia. It is shown that in template-free media, the aggregation of silica particles decreases with ammonia concentrations. Thus, the aggregation degree of formed silica particles may imply whether a silica forming media is suitable for preparing hollow silica microspheres via polystyrene beads templating. The increase in ammonia promotes spontaneous nucleation and condensation of silica oligomers to form silica particles. The repulsive forces between the particles as well as those between them and templates are relatively large, hindering the assembly of silica primary particles on the templates to form silica shells.

A new sand adsorbent for the removal and reuse of nickel ions from aqueous solutions

Nickel ions (Ni(II)) in aqueous solutions were removed by a sand adsorbent with a surface functionalized porous coating. The sand adsorbent has a very large surface area of 150 m2/g. The influence of pH, initial concentration of the solution, temperature, contact time and adsorbent dosage on the removal efficiency of the synthesized sand adsorbent toward Ni(II) in the aqueous solutions were studied. The results indicate that the adsorption of nickel onto the sand adsorbent greatly increases the pH range of 2-4 and slightly increases with temperature from 25 to 40 °C. The maximum removal efficiency and ion retention in per unit mass of the adsorbent were 100% and 5.78 mg/g, respectively, under the specified experimental conditions. The adsorption can be described by the pseudo-second-order kinetic model and the Freundlich adsorption model. The adsorbed nickel (4.24 mg/g) together with the spent adsorbent were successfully employed to prepare a brown glass, suggesting a new way to reutilize the recovered nickel from wastewater and to avoid secondary pollution caused by the used adsorbents.