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A natural clinoptilolite zeolite was modified by ultrasonic-assisted chemicals (NaOH, FeCl 3 and HCl) to improve their performance in ammonium removal from (waste) water. The obtained modified zeolites were characterized by Field Scanning Electron Microscope (FESEM), Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Diffraction (XRD) and gas sorption techniques to understand the relation between physiochemical factors of the modified zeolites and ammonium adsorption. The highest elimination efficiency of ammonium by the natural zeolite modified by ultrasonic-assisted HCl treatment, HZU2, was ≥ 99%. However, ammonium removal by the raw natural zeolite was only 51.66%. The efficiencies of ammonium removal in the presence of various disturbing anions and cations by the HZU2 and raw zeolite were in the range of 79–93% and 15–30%, respectively. The HZU2 was reused five times presenting stable adsorption removal of ammonium. The theoretical calculations were performed to identify the key kinetics and thermodynamics parameters controlling the adsorption rate. The maximum adsorption capacity (q max) of HZU2 obtained by the Langmuir model was about 142.85 (mg-ammonium/g-adsorbent) suggesting that the adsorption capacity of a monolayer and the relative content of alkali metal cations are suitable for the improvement of ammonium ion adsorption. The obtained thermodynamics parameters showed that the ammonium adsorption is a spontaneous and exothermic physisorption process. Consequently, we showed that ultrasonic-assisted chemical modification is a promising approach to control both textural properties and chemical composition of natural zeolites to enhance the ammonium removal from wastewater. [Display omitted] • An efficient approach of clinoptilolite zeolite modification was introduced. • Maximum ammonium adsorption capacity of modified zeolite increased by an order of magnitude. • Zeolite modification resulted higher resistance to disturbing ions in ammonium removal. • Modified zeolite was reusable at least five times. • Key parameters of kinetic and thermodynamic controlling ammonium adsorption were calculated. [ABSTRACT FROM AUTHOR]

Silver nanostructures inside the pores of SBA-15 and plugged SBA-15 were synthesized and imaged, providing for the first time quantitative information about the nanocavity dimensions and plug distributions in plugged SBA-15. [ABSTRACT FROM AUTHOR]

Abstract: Plugged SBA-15 materials consist of mesoporous channels constricted along the central axis by windows. Tailoring and measurement of physical properties, particularly the window sizes, of plugged SBA-15 materials are crucial for potential host–guest applications. In this paper we report a synthesis procedure over a wider range of conditions (temperature and time of synthesis) for tailoring the physical properties of plugged SBA-15 materials and then assess the window sizes for the first time. The plugged SBA-15 materials showed rod-like morphology of 1–3μm in length. The formation of plugged SBA-15 materials was confirmed by X-ray diffraction and N2 physisorption. Each of the plugged SBA-15 materials was modified by a series of alkoxysilanes with increasing alkyl chain length, and the window size was estimated from the shortest alkyl chain length blocking N2 adsorption. The window sizes were approximately 2.3, 2.6 and 3.0nm for plugged SBA-15 synthesized at 70, 80, or 90°C for 1day, respectively and those were 3.1 and 3.9nm for plugged SBA-15 synthesized at 70 and 80°C for 3days. The results showed that increase in the temperature at synthesis time of 1day enhanced both the pore and window sizes, whereas extended synthesis time enhanced the window sizes predominantly. The found trend is that plugged SBA-15 materials lost plugging at extended synthesis times and higher temperatures. Overall, the procedures described here now make it possible to rationally design and synthesize plugged SBA-15 materials for host–guest applications in different fields. [Copyright &y& Elsevier]

Abstract: Spherical silica-based mesocellular foam (MCF) with pores of average size 22nm interconnected by 11.8nm windows was synthesized and then functionalized with alkyl groups using propyl-, butyl-, octyl- and octadecyltrimethoxysilane. Rhizopus oryzae lipase (ROL) was immobilized on MCF and alkyl-functionalized MCF (alkyl-MCF) by physical adsorption. The transesterification reaction activity of (S)-glycidol and vinyl n-butyrate using ROL immobilized on alkyl-MCF increased with increase in alkyl chain length, implying that the more hydrophobic the microenvironment, the greater the activation of ROL. The specific activity of transesterification reaction by ROL immobilized on C18-MCF was 73 times higher than that of free ROL. ROL immobilized on C18-MCF could be reused for eight batches without significant loss of activity. [Copyright &y& Elsevier]

Simultaneous control over particle size and framework Ti content are the major challenges of synthesis of efficient TS-1 catalysts. Here we firstly report control over the particle size and framework Ti content of TS-1 catalysts in a wide range through conventional hydrothermal approach, evaluate catalytic performances of obtained TS-1 catalysts, and then rationally design a novel procedure of synthesis. The characterization of TS-1 catalysts by several techniques revealed that synthesis conditions through conventional hydrothermal approach to reach minimum particle size is different than that to reach maximum framework Ti content. The catalytic study of TS-1 catalysts showed that conversion of phenol (kinetic diameter of 0.57 nm) increased with increase in the particle size, reached a maximum of 29.9% for the TS-1 with particle size of 270 nm, and then dropped significantly for the TS-1 with biggest particle size. The conversion of dibenzothiophene (kinetic diameter of 0.9 nm), however, decreased with increase in the particle size and maximum conversion of 69.0% was achieved by the TS-1 with smallest particle size of 130 nm. No TS-1 catalyst synthesized through conventional approach was efficient in oxidation of the both substrates as the catalyst lacks either small particle size or enhanced framework Ti. Based on the property-function results from conventional synthesis, we rationally designed a novel synthesis of TS-1 with minimum water and optimum pH by (NH 4) 2 CO 3 addition to minimize the particle size and maximize framework Ti content, respectively. The resultant TS-1 with both features of small particle size of 185 nm and enhanced framework Ti resulted in full conversions of phenol and bulky substrate of dibenzothiophene and generates the least amount of wastewater. The new approach applied here is promising and applicable to make efficient Lewis-acid zeolites. Image 1 • Systematic synthesis to understand how framework Ti and crystal size of TS-1 changes upon synthesis conditions. • Evaluation of TS-1 in oxidation of various substrates to clarify contribution of internal and external framework Ti. • Design of TS-1 catalyst based on property-function results from systematic study. • Synthesis of efficient TS-1 catalyst with minimum amount of wastewater generation. • Rational synthesis of TS-1 with superior catalytic performance toward oxidation of substrates with different sizes. [ABSTRACT FROM AUTHOR]

This study reports a seeding-polymer-assisted method using inexpensive tetrapropylammonium bromide (TPABr) to synthesize titanium silicalite-1 (TS-1) ranging from supported embryonic (<8 nm) to crystalline nano-/micrometersized (≈0.1–1.0 μm) particles by kinetic regulation. The in situ grown embryonic TS-1 on the amorphous silica presents defective Ti(OH)(OSi) 3 , tetrahedral framework Ti ("TiO 4 "), and extraframework Ti ("TiO 6 ") species, while crystalline nano-/micro-metersized TS-1 particles exhibit either "TiO 4 " or both "TiO 4 " and "TiO 6 " species and a smaller external surface area, S ext. Turnover frequency (TOF) of TS-1 catalysts in the oxidation of dibenzothiophene (DBT) changes by an order of magnitude with the alteration of active Ti species. For instance, the TOF of supported embryonic TS-1 is 224.3 h−1 while it is 32.6 h−1 for the micro-metersized particles due to differences in the active Ti species. However, the TOF of the different TS-1 samples with similar Ti active sites scales only in proportion to S ext. The supported embryonic TS-1 on amorphous silica presents similar structural and chemical stability in comparison with crystalline nano-/micro-metersized TS-1 catalysts under water-free reaction conditions. Consequently, in situ prepared supported embryonic TS-1 combining improved accessibility (via increased external surface area) of different types of Ti species is a promising alternative for the conversion of bulky substrates. [Display omitted] • A feasible approach for the in situ synthesis of supported embryonic TS-1 with various Ti active sites was introduced. • Catalytic activity of supported embryonic TS-1 was an order of magnitude higher than the micro-metersized crystalline TS-1. • Stability study of the supported embryonic TS-1 in the presence of water was conducted. • The supported embryonic TS-1 was reusable. [ABSTRACT FROM AUTHOR]