Sodium niobate adsorbents doped with tantalum (TaV) for the removal of bivalent radioactive ions in waste waters

Sodium niobates doped with different amount of tantalum (TaV) were prepared via thermal reaction process. It was found pure nanofibril and bar-like solids can be obtained when tantalum was introduced into the reaction system. For the well-crystallized fibril solids, the Na+ ions are difficult to be exchanged, and the radioactive ions such as Sr2+ and Ra2+ ions just deposit on the surface of the fibers during the sorption process, resulting in lower sorption capacity and distribution coefficients (Kd)`. However, the bar-like solids are poorly-crystallized and have lots of exchangeable Na+ ions. They are able to remove highly hazardous bivalent radioactive isotopes such as Sr2+ and Ra2+ ions. Even in the presence of lots of Na+ ions, they also have higher Kd. More importantly, such sorption finally intelligently triggers considerable collapse of the structure, resulting in the entrapment of the toxic bivalent cations permanently in the solids so that they can be safely disposed. This study highlights new opportunities for the preparation of Nb-based adsorbents to efficiently remove the toxic radioactive ions from contaminated water

Integrating efficient filtration and visible-light photocatalysis by loading Ag-doped zeolite Y particles on filtration membrane of alumina nanofibers

Filtration membrane technology has already been employed to remove various organic effluents produced from the textile, paper, plastic, leather, food and mineral processing industries. To improve membrane efficiency and alleviate membrane fouling, an integrated approach is adopted that combines membrane filtration and photocatalysis technology. In this study, alumina nanofiber (AF) membranes with pore size of about 10 nm (determined by the liquid-liquid displacement method) have been synthesized through an in situ hydrothermal reaction, which permitted a large flux and achieved high selectivity. Silver nanoparticles (Ag NPs) are subsequently doped on the nanofibers of the membranes. Silver nanoparticles can strongly absorb visible light due to the surface plasmon resonance (SPR) effect, and thus induce photocatalytic degradation of organic dyes, including anionic, cationic and neutral dyes, under visible light irradiation. In this integrated system, the dyes are retained on the membrane surface, their concentration in the vicinity of the Ag NPs are high and thus can be efficiently decomposed. Meanwhile, the usual flux deterioration caused by the accumulation of the filtered dyes in the passage pores can be avoided. For example, when an aqueous solution containing methylene blue is processed using an integrated membrane, a large flux of 200 L m-2 h-1 and a stable permeating selectivity of 85% were achieved. The combined photocatalysis and filtration function leads to superior performance of the integrated membranes, which have a potential to be used for the removal of organic pollutants in drinking water

Ceramic membranes for separation of proteins and DNA through in situ growth of alumina nanofibres inside porous substrates

Ceramic membranes were fabricated by in situ synthesis of alumina nanofibres in the pores of an alumina support as a separation layer, and exhibited a high permeation selectivity for bovine serum albumin relative to bovine hemoglobin (over 60 times) and can effectively retain DNA molecules at high fluxes

One-step synthesis of hydrothermally stable mesoporous aluminosilicates with strong acidity

ing tetraethylorthosilicate (TEOS), polymethylhydrosiloxane (PMHS) and aluminium isopropoxide (AIP) as the reactants, through a one-step nonsurfactant route based on PMHS-TEOS-AIP co-polycondensation, hydrothermally stable mesoporous aluminosilicates with different Si/Al molar ratios were successfully prepared. All samples exclusively showed narrow pore size distribution centered at 3.6 nm. To assess the hydrothermal stability, samples were subjected to 100 àdistilled water for 300 h. The boiled mesoporous aluminosilicates have nearly the same N2 adsorption-desorption isotherms and the same pore size distributions as those newly synthesized ones, indicating excellent hydrothermal stability. The 29Si MAS NMR spectra confirmed that PMHS and TEOS have jointly condensed and CH3 groups have been introduced into the materials. The 27Al MAS NMR spectra indicated that Al atoms have been incorporated in the mesopore frameworks. The NH3 temperature-programmed desorption showed strong acidity. Due to the existence of large amount of CH3 groups, the mesoporous aluminosilicates obtained good hydrophobicity. Owing to the relatively large pore and the strong acidity provided by the uniform four-coordinated Al atoms, the excellent catalytic performance for 1,3,5-triisopropylbenzene cracking was acquired easily. The materials may be a profitable complement for the synthesis of solid acid catalysts.No Full Tex

A novel moisture-resistant film for NiSO4.6H2O filter based on isophorone diisocyanate-bridged polysilsesquioxane

A new bridged silsesquioxane (BSQ) was synthesized with isophorone diisocyanate (IPDI) and 3-aminopropyltriethoxysilane (APTES). Highly cross-linked bridged polysilsesquioxane (BPSQ) sol was prepared by the sol-gel polycondensation of the as-synthesized BSQ under basic catalysis. Transparent film was obtained by dip-coating the BPSQ sol on the nickel sulfate hexhydrate (NSH, NiSO4綈2O) crystal wafer, an important kind of UV light filter used at wavelength 300 nm. The obtained BPSQ film was nonporous (pore volume is 2 נ10-3 cm3 g-1) and exhibited very high condensation degree of siloxane (99.0%). This film showed high optical transmittance and excellent moisture-resistant protection to the NSH filter. Moreover, the thermal stability of the NSH filter was also greatly improved by the as-prepared BPSQ film.No Full Tex

Adsorption of the herbicide simazine on moderately acid-activated beidellite

This study focuses on acid activated beidellite and its adsorption ability for the herbicide simazine. After acid activation, the non-silicon atoms, such as Al, Mg, and Fe, which are located in the octahedral sheet, and sodium ions between the clay mineral layers were leached from the parent clay mineral. The basal spacing increased after acid activation. The acid activated beidellites were used to remove simazine from water. The simazine molecules can enter into the destroyed alumino silicate interlayer spaces and can be adsorbed from contaminated water.No Full Tex

Effect of ethanol washing of titania clay mineral composites on photocatalysis for phenol decomposition

A mesoporous material of titania and clay minerals was prepared from TiOSO4 and Laponite, hectorite, beidellite and saponite. The impact of ethanol washing before calcination on the structure and photocatalytic activity for phenol decomposition was investigated. As comparison, conventional titania pillared clay minerals were also prepared. The mesoporous material had more mesopores and better crystallized anatase particles than conventional pillared clay minerals. The photocatalytic activity of the mesoporous material was far better than that of the conventional pillared clay minerals. Thus, mesopores and larger anatase crystals were beneficial to the photocatalysis. The specific surface area and pore volume of the mesoporous material, which was obtained by washing with ethanol, were larger than those of the sample without ethanol washing. The photocatalytic activity of the ethanol washed samples was 2-6 times higher than that of the corresponding sample without ethanol washing. The main reasons for the high activity were the ethanol washed samples had larger specific surface area and pore volume, and they could be readily dispersed in water. The structure of samples was investigated by XRD, TEM equipped with EDS and N2 adsorption-desorption method.No Full Tex

Tuning pore size and hydrophobicity of macroporous hybrid silica films with high optical transmittance by a non-template route

Macroporous silica films with methyl groups grafted on their surface were prepared from polymethylhydrosiloxane (PMHS) and tetraethylorthosilicate (TEOS) without templates. Compared to the conventional template syntheses, this approach has several advantages. First, it avoids the removal of templates, which is sometimes an environmentally unfriendly procedure. Second, it does not require a post-synthesis grafting to form the hybrid structures with methyl groups on the silica surface. Third, the pore size and hydrophobicity (expressed by the water contact angle) of the film can be tuned readily. By adjusting the amount of PMHS used in the synthesis and introducing hexamethyldisilazane (HMDS) we can tune the pore size in a wide range from 50 nm to 500 nm. The hydrophobicity increases substantially as the pore size decreases. Evidently, the reaction mechanism of this synthesis is different from the conventional template synthesis. A tentative mechanism is proposed: the hydrogen gas released from PMHS results in the formation of the macropores in the films. With excellent hydrophobicity, optical transmittance and thermal stability, the obtained silica films have potential applications in the semiconductor industry.No Full Tex