Self-assembled mesoporous hierarchical-like In2S3 hollow microspheres composed of nanofibers and nanosheets and their photocatalytic activity.

Novel template-free hierarchical-like In(2)S(3) hollow microspheres were synthesized using thiosemicarbazide (NH(2)NHCSNH(2)) as both a sulfur source and a capping ligand in a ethanol/water system. In this study, we demonstrate that several process parameters, such as the reaction time and precursor ratio, strongly influence the morphology of the final product. The In(NO(3))(3)/thiosemicarbazide ratios were found to effectively play crucial roles in the morphologies of the hierarchical-like In(2)S(3) hollow microsphere nanostructure. With the ratios increasing from two to four, the In(2)S(3) crystals exhibited almost spherical morphologies. The synthesized products have been characterized by a variety of methods, including X-ray powder diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffused reflectance spectroscopy (UV-vis DRS). XRD analysis confirmed the tetragonal structure of the In(2)S(3) hollow microspheres. The products show complex hierarchical structures assembled from nanoscale building blocks. The morphology evolution can be realized on both outside (surface) and inside (hollow cavity) the microsphere. The surface area analysis showed that the porous In(2)S(3) possesses a specific surface area of 108 m(2)/g and uniform distribution of pore sizes corresponding to the size of pores resulting from the self-assembled structures with flakes. The optical properties of In(2)S(3) were also investigated by UV-vis DRS, which indicated that our In(2)S(3) microsphere samples possess a band gap of ∼1.96 eV. Furthermore, the photocatalytic activity studies revealed that the synthesized In(2)S(3) hollow microspheres exhibit an excellent photocatalytic performance in rapidly degrading aqueous methylene blue dye solution under visible light irradiation. These results suggest that In(2)S(3) hollow microspheres will be an interesting candidate for photocatalytic detoxification studies under visible light radiation.

CdS microspheres composed of nanocrystals and their photocatalytic activity.

A simple and template-free solution phase synthesis method has been developed for the preparation of novel CdS hollow microspheres using cadmium nitrate and thioacetamide precursors. In this manuscript, we demonstrate that process parameters such as the reaction time, precursor ratio, and reaction temperature strongly influence the morphology of the final product. The synthesized products have been characterized by a variety of methods, including X-ray powder diffraction (XRD), Raman spectroscopy, high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray diffraction (EDX) analysis, X-ray photoelectron spectroscopy (XPS), and UV-visible diffused reflectance spectroscopy (UV-DRS). XRD analysis confirmed the cubic structure of the CdS microspheres, which has also been further supported by Raman spectroscopy. The HR-SEM measurements revealed the spherical morphology of the CdS microspheres which has been evolved by the oriented aggregation of the primary CdS nanocrystals. The TEM measurements confirmed the hollow shell-like structure of the spheres; the formation of their hollow interiors can be explained by the Ostwald ripening mechanism. UV-DRS studies showed that the band gap of the CdS microspheres increased with increasing cadmium-nitrate-to-thioacetamide ratio. Furthermore, studies of photocatalytic activity revealed that the synthesized CdS hollow microspheres exhibit an excellent photocatalytic performance in rapidly degrading methyl tert-butyl ether (MTBE) in aqueous solution under visible-light illumination. These results suggest that CdS microspheres will be an interesting candidate for photocatalytic detoxification studies under visible light radiation.

Cauliflower-like CdS microspheres composed of nanocrystals and their physicochemical properties.

Cauliflower-like cadmium sulfide (CdS) microspheres composed of nanocrystals have been successfully synthesized by a hydrothermal method using poly(ethylene glycol) (PEG) as the template coordination agent and characterized by a variety of methods. Our experiments confirmed that the size of the CdS microspheres could be easily modified by controlling the chain length of PEG. Powder X-ray diffraction and Raman spectroscopy measurements revealed the cubic structure of the CdS microspheres; morphological studies performed by HR-SEM and HR-TEM methods showed the cauliflower-like structure of the synthesized CdS microspheres. Each microsphere was identified to be created by the self-assembly of CdS nanocrystals and is attributed to the oriented aggregation of the CdS nanocrystals around a polymer-Cd(2+) complex spherical framework structure. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) analysis confirmed the stoichiometries of the CdS microspheres. Diffuse reflectance spectrum (DRS) measurements showed that increasing the PEG chain length increased the band gap value of the CdS microspheres slightly, from 1.99 to 2.06 eV. The cauliflower-like CdS microspheres could be applied to photocatalytic degradation studies.

Adsorption characteristics of Cu(II) onto ion exchange resins 252H and 1500H: kinetics, isotherms and error analysis.

The adsorption of Copper(II) onto Amberjet 1500H and Ambersep 252H synthetic ion exchange resins have been studied. All the studies were conducted by a batch method to determine equilibrium and kinetic studies at the solution pH of 5.8 in the concentration ranges from 10 to 20mg/L. The experimental isotherm data were analyzed using the Freundlich, Langmuir, Redlich Perterson, Temkin, Dubinin-Radushkevich equations. Correlation co-efficient was determined for each isotherm analysis. Error functions have been used to determine the alternative single component parameters by non-linear regression due to the bias in using the correlation coefficient resulting from linearisation. From the error analysis the EABS error function provides the best parameters for the isotherm equation in this system. Adsorption kinetics data were tested using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The initial sorption rate, pseudo-first-order, pseudo-second-order and intraparticle diffusion rate constants for different initial concentrations were evaluated and discussed.

RETRACTED: Photocatalytic activity of Bi-doped TiO(2) in the degradation of monocrotophos in aqueous solution.

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Removal of copper from aqueous solution by aminated and protonated mesoporous aluminas: kinetics and equilibrium.

A novel adsorbent, aminated and protonated mesoporous alumina, was prepared and employed for the removal of copper from aqueous solution at concentrations between 5 and 30 mg/l, in batch equilibrium experiments, in order to determine its adsorption properties. The removal of copper by the adsorbents increases with increasing adsorbent dosages. The adsorption mechanism is assumed to be an ion exchange between copper and the hydrogen ions present on the surface of the mesoporous alumina. The adsorbent was characterized by XRD, TEM, SEM, and BET methods. The sorption data have been analyzed and fitted to linearized adsorption isotherm of the Freundlich, Langmuir, and Redlich-Peterson models. The batch sorption kinetics have been tested for first-order, pseudo-first-order, and pseudo-second-order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated. Results also showed that the intraparticle diffusion of Cu(II) on the mesoporous catalyst was the main rate-limiting step.

Arsenic removal using mesoporous alumina prepared via a templating method.

The health threat of arsenic is well-known, and the U.S. EPA recommends the maximum contaminant level to be 0.01 ppm or less for arsenic in drinking water. Therefore, advanced treatment processes are needed for finished water to meet the required regulations. Adsorption is considered to be a less expensive procedure that is safer to handle than precipitation, ion exchange, and membrane filtration. Activated alumina (AA) is the most commonly used adsorbent for the removal of arsenic from aqueous solutions. However, conventional porous solids including AA have ill-defined pore structures and, typically, low adsorption capacities and act in a kinetically slow manner. An ideal adsorbent should have uniformly accessible pores, an interlinked pore system, a high surface area, and physical and/or chemical stability. To meet this requirement, mesoprous alumina (MA) with a wide surface area (307 m2/g) and uniform pore size (3.5 nm) was prepared, and a spongelike interlinked pore system was developed through a post-hydrolysis method. The resulting MA was insoluble and stable within the range of pH 3-7. The maximum uptake of As(V) by MA was found to be 7 times higher [121 mg of As(V)/g and 47 mg of As(III)/ g] than that of conventional AA, and the kinetics of adsorption were also rapid with complete adsorption in less than 5 h as compared to the conventional AA (about 2 d to reach half of the equilibrium value). A desorption study using sodium hydroxide solutions (0.01-1 M) was conducted, and 0.05 M NaOH was found to be the most suitable desorption agent. More than 85% of the arsenic adsorbed to the MA was desorbed in less than 1 h. Several other activated aluminas with different pore properties were also tested. The results show that the surface area of the adsorbents does not greatly influence on the adsorption capacity. In fact, the key factor is a uniform pore size and an interlinked pore system. These studies show that MA with a wide surface area, uniform pore size, and interlinked pore system can be used as an efficient adsorbent for the removal of arsenic.