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Papers by Tarek Salama

Al-Azhar Bulletin of Science, 2008

Encapsulation of nickel(II) complex of the Schiff base-type ligand (salicylidene-paminobenzoic ac... more Encapsulation of nickel(II) complex of the Schiff base-type ligand (salicylidene-paminobenzoic acid) in the intracrysatalline nano-pores of zeolite-Y is reported. The zeoliteencapsulated trinuclear Ni(II)-Schiff base complex was prepared by diffusion of the ligand through pores of the zeolite, already exchanged with the respective metal (flexible ligand method). The host/guest compound obtained was characterized by elemental analysis, spectroscopic (IR and electronic) studies, surface texture, thermal analysis and powder x-ray diffraction (XRD). The solids were subjected to in situ FT-IR study of adsorbed carbon monoxide. IR and UV-vis as well as XRD data indicate that the chemical stoichiometry of the complex remains intact upon encapsulation and the geometric environment around the metal ions is a distorted tetrahedral. Experimental evidence indicates that the chemisorption of carbon monoxide is indeed catalyzed by the zeolite-encapsulated complex. Sorption of CO results in the appearance of a series of surface carbonyl species: linear Ni II-CO (2198 cm −1), bridged CO (1896 cm −1), C=O derived from acetone-like species (1728 and 1686 cm-1) and physisorbed CO 2 (2351 cm −1). The acetone-like species are stable upon evacuation which can be considered as bound to Lewis acid sites in the zeolite Y. These species are most significant on the zeolite-encapsulated complex than on metal-exchanged zeolite.

Journal of Macromolecular Science, Part A, 2019

Hybrid oligomers composed of polyurethane methacrylate (PUMA) and polyurethane acrylate (PUA) wer... more Hybrid oligomers composed of polyurethane methacrylate (PUMA) and polyurethane acrylate (PUA) were synthesized by poly addition polymerization of polypropylene glycol (PPG 1000), 2,4and 2,6-toluen diisocyanate (TDI 80/20) and 2-hydroxyethyl methacrylate or 2-hydroxyethyl acrylate. Isopropanol was served as the isocyanate blocking agent. The grafting of either PUMA or PUA oligomers to the vinyl acetate monomer was implemented for the first time for improving the properties of the produced PU-co-VAc or (PUP MA or PUP A) terpolymers as new binders for emulsion coating formulations. The synthesized terpolymers were characterized with Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1 H NMR), scanning electron microscope (SEM), gel permeation chromatography (GPC), minimum film forming temperature (MFFT), thermal gravimetric analysis (TGA), Zeta potential and mechanical properties. It has been shown that properties of the terpolymers and their corresponding films were greatly influenced by the grafting of PUMA and PUA at a low concentration level (5 wt%). Cured films of PU based vinyl acetate (PUP MA or PUP A) exhibited higher thermal stability and less weight loss compared to the vinyl acetate copolymer (PVAC). The synthesized PUP MA and PUP A terpolymers revealed enhanced efficiency as binders for emulsion paints in comparison to the PVAC copolymer.

Chemical Sciences Journal, 2016

Zeolite Y in the sodium form (NaY) was synthesized using amorphous silica ash derived from waste ... more Zeolite Y in the sodium form (NaY) was synthesized using amorphous silica ash derived from waste rice husks under hydrothermal conditions. Structural characterization of NaY before and after modification with ZnO and ZnS has been done using powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N 2 adsorption-desorption at-196 °C, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The effects of the Na 2 O/SiO 2 and Si/Al ratios, aging temperature and crystallization time on the optimized synthesis of NaY were thoroughly investigated. Thus the regulated Na + impurity concentration in the starting hydrogel was found to act as a template-assisted synthesis of zeolite NaY by the potential incorporation of Al atoms into the zeolite framework. Results of surface analyses indicate that the interactions of ZnO and ZnS with NaY zeolite are distinguishable and thus the higher interaction is observed for the latter. While Zn II has experienced electrostatic bonding interaction with the framework oxygen atoms, creation of mesopores in NaY due to local destruction of the zeolite lattice around the growing ZnS particles was evidenced. Wonderfully, ZnS/NaY exhibited a high performance in prohibiting the growth of Escherichia coli (E. coli) and negligible from P. Aeruginosa, and these important features make it a potential candidate as an antimicrobial agent for controlling implant-related infections.

Colloids and Surfaces a Physicochemical and Engineering Aspects, Jul 30, 2002

Science China Materials, 2015

functional performance of the different kinds of zeolites, many studies have been devoted to impr... more functional performance of the different kinds of zeolites, many studies have been devoted to improving synthetic approaches to control crystal size, the size of the intracrystalline pore/channel system and morphology of zeolites [5,6]. Among various types of zeolites, NaP (Na 6 [(AlO 2) 6 (SiO 2) 10 ]⋅15H 2 O) is one of the most interesting structured zeolite with two sets of intersecting channels: 0.31 nm × 0.44 nm and 0.26 nm × 0.49 nm. According to International Zeolite Association (IZA), this structure is called "Gismondine" (GIS) framework topology [7,8]. NaP zeolite offers the greatest promise for gas separation applications due to its small pore size [9,10], and is also useful for removal of toxic and radioactive waste species like Cs, Sr, Ba, Pb, U, heavy metals, and ammonium from wastewater, seawater potassium extraction and formation of environmental friendly detergent [11,12]. NaP zeolite can be synthesized from various precursor materials and various methods. It can be synthesized from: (i) clay at a crystallization temperature of 85ºC [13], (ii) sodium silicate solution [14], and (iii) high silicon fly ash of coal combustion at 120ºC for 4 h [15]. Among them the most common methods used for the synthesis of NaP zeolite are the sol-gel technique, hydrothermal synthesis and microwave heating synthesis [1]. The NaP zeolite with different morphologies can offer many intriguing properties: places to store the guest molecules and to perform chemical reactions with selected-sized molecules. Thus, the NaP zeolite morphology and its important correlation with properties is the need of the recent research. In this work, we attempted the template free hydrothermal synthesis of NaP under controlled conditions. Based on multiple paths that can be involved in the hydrothermal synthesis of NaP, optimization of crystallization conditions was adapted through variation of the following parameters: Na 2 O/SiO 2 and SiO 2 /Al 2 O 3 molar ratios, aging time and aging temperature. The characteristics of the synthesized gels NaP zeolite particles were prepared through a template-free hydrothermal condition at 100ºC. Parameters like Na2O/SiO2 and SiO2/Al2O3 molar ratios, gel aging time and aging temperature were investigated for regulating the crystallization of the final product. The samples at different synthesis stages were characterized with N2 adsorption at −196ºC, field emission scanning electron microscopy (FE-SEM), temperature programmed desorption of ammonia adsorption, X-ray diffraction, thermogravimetric and differential scanning calorimetry analysis and Fourier transform infrared spectroscopy. The experimental results evidenced that a high ordering crystallinity of NaP zeolite was obtained at Na2O/SiO2 and SiO2/Al2O3 molar ratios of 1.10 and 1.40, respectively, and a temperature of 100°C for 4 days of aging. FE-SEM image exhibited polycrystalline aggregates of NaP zeolite with crystallite sizes ranging up to 5.04 μm with cactus/cabbage like structures. The quantitative analysis of the total number of acid sites was found to increase as Na2O increases. The NaP zeolite sample with a Na2O/SiO2 molar ratio of 1.13 exhibited a large fraction of the acid sites on its external surface, contrary to that synthesized with a relevant ratio of 1.10. The optimized NaP zeolite could be successfully bestowed with excellent sorption properties of Ca(II) in aqueous solution. The kinetic parameters for Ca(II) adsorption were thoroughly investigated.

Applied Catalysis B: Environmental, 2016

Highly stable and magnetically recoverable MFe 2 O 4 (M= Zn, Co, Mn) spinel ferrite nanoparticles... more Highly stable and magnetically recoverable MFe 2 O 4 (M= Zn, Co, Mn) spinel ferrite nanoparticles; synthesized using sol gel-hydrothermal technology via utilizing polyvinyl alcohol surfactant, were proposed as heterogeneous catalysts for the reduction of nitroarenes. The morphological characteristics, structural exploration, surface, optical, and vibrational properties were performed using powder X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive X-ray, N 2 sorptiometry, diffused UV-visible reflectance spectroscopy. The results showed that MnFe 2 O 4 exhibited the best performance in the reduction of 4-nitrophenol (4-NP), 2,4,6 tri-nitrophenol (2,4,6-NP) and 4-nitroaniline (4-NA) and revealed 100% conversion into the corresponding amino derivatives in 270 sec with rate constant equal 0.01061 sec-1 , 0.01134 sec-1 and 0.01355 sec-1 , respectively. The superiority of the catalytic reduction of MnFe 2 O 4 was due to increasing the pore radius and pore volume (6.75 nm, 0.227 cc/g) values compared to other nanoferrites. The synthesized nanoferrites indicate independence of the activity on crystallite sizes due to the insignificant margin of change (from 6 to10 nm). Conversely, decreasing the activity of ZnFe 2 O 4 was due to increasing the Zn 2+ ions size that induces an increase in lattice parameter values and thus increases the long-range electron transfer between Fe 2+-Fe 3+ ions. The MnFe 2 O 4 catalyst that presented the highest saturation magnetization (135 emu/g) indicated the highest reduction potential for 4-NA comparatively in the presence of NaBH 4 and the reduction reaction followed pseudo first-order kinetics. Increasing the reduction performance of 4-NA compared to other nitroaromatics on MnFe 2 O 4 was explained based on the formed intermediates, their reactivities, and hydrophobicites.

Environmental Technology & Innovation, 2015

ABSTRACT Rice husk was chemically modified with synthesized hexadecylpyridinium bromide (HDPBr) t... more ABSTRACT Rice husk was chemically modified with synthesized hexadecylpyridinium bromide (HDPBr) to enhance Cr(VI) adsorption capacity of the obtained surfactant modified rice husk (HDP+/RH). The structure of as-synthesized HDPBr surfactant was confirmed with 1H NMR spectroscopy. The interaction between the HDPBr molecules and the RH surface was investigated by X-ray diffraction (XRD), FTIR spectroscopy, scanning electron microscopy (SEM) and nitrogen adsorption at −196 °C. HDP+/RH brought about decrease in the values of specific surface area, pore radius, pore size and pore volume compared with those of pure RH, indicating pore narrowing through grafting of HDPBr on the RH surface. The IR spectrum of HDP+/RH exhibited new frequency peaks at 1614, 1490, 1115 and 1043 cm−1 due to vibration of pyridinium ion, fact that is indicative of the successfully anchoring of the surfactant molecules through hydrophobic bonding to the cellulose chains in RH. The adsorption of Cr(VI)-oxyanions onto RH and HDP+/RH was investigated by batch studies at 20 and 50 mg L−1 initial concentration. HDP+/RH was evaluated as an efficient adsorbent for the Cr(IV)-oxyanions than RH, which rapidly attained equilibrium after 45 min compared with the latter at 110 min. This allows evidence for the electrostatic interaction between the Cr(VI)-oxyanions and HDP+-promoted RH. The adsorption data fitted reasonably with the Langmuir and Freundlich models for HDP+/RH, similarly the pseudo-second-order model shows a better fitting. The intraparticle diffusion analysis suggests that adsorption of Cr(VI) ions by HDP+/RH involved intraparticle diffusion which contributed to the rate of the process.

Journal of Sol-Gel Science and Technology, 2015

Silver nanoparticles embedded in a carboxymethyl cellulose matrix (AgNPs/CMC) were synthesized by... more Silver nanoparticles embedded in a carboxymethyl cellulose matrix (AgNPs/CMC) were synthesized by a UV irradiation technique. The successful formation of AgNPs/CMC was examined using UV-Vis spectroscopy, XPS, XRD, TEM, and FTIR. The factors in the preparation process that affected the final products were extensively studied. Thus, 5.0 mM AgNO 3 , 0.5 g l-1 CMC, and exposure to UV light for 2.5 min provide excellent combinations to accomplish the AgNPs/CMC formation. Measurements of optical spectra showed that the surface plasmon resonance was localized around 426 nm when the reaction mixture exposed to UV light for 0.5 min; that is monotonically blue shifted to 403 nm up to 2.5 min exposure time. This is manifested in a quick reduction of Ag ? into smaller Ag nanoparticles. The IR analysis indicated that hydroxyl and carboxylate groups in CMC were included in coordination with the Ag ? ions through displacement of one proton. Upon absorbing UV light, the cellulose hydroxyl and carboxymethylic groups get excited, which reduce Ag ? ions to Ag nanoparticles. The TEM image for the optimal designed AgNPs/CMC sample confirmed that AgNPs are formed with many individual spherical shapes and an average diameter of 15.5 nm. This AgNPs/CMC sample showed promising antibacterial properties toward E. coli.

Studies in Surface Science and Catalysis, 1997

The role of hydrogen in the selective reduction of NO by CO over Au/NaY catalysts has been discus... more The role of hydrogen in the selective reduction of NO by CO over Au/NaY catalysts has been discussed. The NCO intermediates detected by FT-IR absorption at 423–573 K shows a dependence on the presence of H2 which functions in N-O dissociation. The yields of N2 and CO2 were increased in the presence of hydrogen when NCO complexes were present in the gold catalyst up to 573 K. Above this temperature, where direct NO+CO is the only competing reaction, the presence of hydrogen reduced conversions. The results indicated that dual AuI and AuO sites are effective in maintaining higher activities of gold catalysts for the above reaction. The AuI species gave a characteristic carbonyl IR absorbing band at 2188 cm−1.

J. Chem. Soc., Faraday Trans., 1993

ABSTRACT

Journal of the Chemical Society, Faraday Transactions, 1990

ABSTRACT

ChemInform, 2010

Gold(I) Prepared by Monolayer Dispersion of AuCl3 inside Na-Y Zeolite.-Physically mixed samples o... more Gold(I) Prepared by Monolayer Dispersion of AuCl3 inside Na-Y Zeolite.-Physically mixed samples of Au2Cl6 with partially dehydrated Na-Y zeolite prepared at room temperature under N2 atmosphere are thermally evacuated at 323 K for 72 h. Studies of the structural changes of the Au2Cl6 species show the formation of a crystalline phase due to condensation of Au species on the zeolite surface. The crystalline phase disappears on further heating to 338 K due to vaporizing of the crystals and diffusion of Au2Cl6 vapors into the cages and channels of the zeolite. The migration is associated with a partial reduction of Au(III) to Au(I) ions by formation of (AuCl)n zigzag chains. Au-O interactions at 323 K shown by the EXAFS data result from interactions of Au2Cl6 with traces of H2O in Na-Y.-(SALAMA, T.

Surface Science, 1990

ABSTRACT

Reaction Kinetics & Catalysis Letters, 1992

Platinum catalysts supported on a TiO 2 phase welldispersed on Si02 (Ti02/SiO 2) exhibited a high... more Platinum catalysts supported on a TiO 2 phase welldispersed on Si02 (Ti02/SiO 2) exhibited a high activity for butane hydrogenolysis; activity was I~ 2 orders of magnitude higher than those of platinum catalysts supported on Si02 and TiO 2. KaTaaH3aTop~ Pt, HaHeCeHHNe Ha Ti02, xopomo aMcnepcMpOBaHH~M Ha ca~e Si02 (Ti02/Si02), o6aa~a~r BNCOKOM aKTHBHOCTSD K FMBpoFeHO~M3y 6yTaHa; 9Ta aKTMBHOCTb OKa~8~ZC5 Ha 1 ~ 2 no

Microporous and Mesoporous Materials, 2005

High silica mordenite samples (Si/Al molar ratios 38 and 60) were synthesized hydrothermally at 4... more High silica mordenite samples (Si/Al molar ratios 38 and 60) were synthesized hydrothermally at 433 K with the template route method using o-phenylenediamine and characterized with several techniques including XRD, FT-IR, TG/DTA, pyridine-FTIR and N 2 adsorption. The effects ...

Microporous and Mesoporous Materials, 2006

Copper(II) complex with Schiff base ligand derived from salicyaldehyde and p-aminobenzoic acid wa... more Copper(II) complex with Schiff base ligand derived from salicyaldehyde and p-aminobenzoic acid was encapsulated in the intracrystalline cavities of NaY zeolite via “ship-in-the-bottle” (in situ assembling of the metal complex from smaller moieties) technique. A comparative FT-IR spectroscopic study of CO adsorption on simple Cu ion exchanged zeolite and the encapsulated complex has been carried out. Detailed characterization of the

Microporous and Mesoporous Materials, 2008

Copper(I)-salen: N,N À-ethylenebis(salicylidene-iminato)copper(I), immobilized into the structure... more Copper(I)-salen: N,N À-ethylenebis(salicylidene-iminato)copper(I), immobilized into the structure of Al-MCM-41 has been synthesized by a liquid-phase adsorption of salen through Cu(I)-exchanged Al-MCM-41 (Cu(I)-salen/M imp) and by a flexible ligand method (Cu(I)-salen/M ss). The ligand and complex were characterized by various physico-chemical measurements such as elemental analysis, powder XRD, mid-spectral FT-IR, thermal analysis (TGA, DTGA), surface texture and scanning electron microscopy (SEM). A comparative in situ FT-IR study of CO adsorption onto simple Cu(I)-exchanged Al-MCM-41 and the complex-immobilized Al-MCM-41 has been carried out. The structure of Al-MCM-41 after modification remains intact, which was evident from XRD and FT-IR studies. The surface characteristics and thermal analysis have provided evidence for successful immobilization of the copper complex inside Al-MCM-41. The structure of Cu(I)-salen complex in Al-MCM-41 prepared by the liquid-phase adsorption of salen was more thermally stable than the analogous prepared by the flexible ligand method. The in situ FT-IR investigation of CO adsorption showed a band at 2124 cm À1 due to Cu(I)-CO in the spectrum of Cu(I)-exchanged Al-MCM-41. This band was shifted to 2146 cm À1 in the spectra of Al-MCM-41-containing complex due to a stronger mode of CO interaction. The Cu(I)-salen/M imp sample was more active than the Cu(I)-salen/M ss one in the generation of CO 2 (2336 cm À1), which was produced from CO and H 2 O by the water-gas shift reaction. Surface bound adsorbed species like carbonate (1636, 1590, 1488 and 1434 cm À1) and formate (1727 cm À1) were also detected. The spectrum of the Cu(I)-salen/M ss sample was characterized by a band at 2278 cm À1 assigned to isocyanate ion, NCO À , coordinated to a Cu(I) ion which was absent in the spectra of other samples. The extent of this band depends on the interaction of the immobilized complex with the Al-MCM-41 lattice.

Microporous and Mesoporous Materials, 2006

The interaction between Mo (2–30wt.% expressed as MoO3) and NaY zeolite lattice by applying conve... more The interaction between Mo (2–30wt.% expressed as MoO3) and NaY zeolite lattice by applying conventional impregnation with aqueous (NH4) 6Mo7O24· 4H2O (AHM) and vapor-phase deposition of volatile complex Mo (CO) 6 has been compared. The samples were ...

Microporous and Mesoporous Materials, 2012

Extracted silica and lignin from local rice straw were respectively used as a source of silica an... more Extracted silica and lignin from local rice straw were respectively used as a source of silica and a templating agent for the synthesis of nanosized ZSM-5 zeolite at different aging temperatures with the autoclave process. A comparative analysis between synthesized ZSM-5 with lignin (Z L) and its respective synthesized with most common tetrapropyl-ammonium bromide (TPABr) (Z T) using XRD, FT-IR, TEM, TGA/ DTGA and pore structure analysis by N 2 adsorption at À196°C was conducted. A higher degree of crystallinity and a larger specific surface area (S BET) were presented for Z L at aging temperature of 160 than at 140°C. Concurrently, a decrease in intensity of the diffraction line at d = 3.342 Å A 0 due to a-quartz silica was seen, giving rise to an increase of the dissolution rate of silica component in the gel phase at 160 over 140°C. Complementary TEM and XRD techniques informed that the particle sizes measured 50 and 75 nm for the former and latter, respectively. The Z L surface was modified with TPA + (50-200 mmol) and applied for chromate anions (5-30 ppm) adsorption experiments in the aqueous solution at room temperature and pH 5. The capacity of chromate adsorption over Z L-modified TPA + was greater by threefold than over Z L by the combination of electrostatic effects. The kinetics obeyed Freundlich model where the adsorption onto Z L-modified TPA + affords 3.7 mmol/g.

Al-Azhar Bulletin of Science, 2008

Encapsulation of nickel(II) complex of the Schiff base-type ligand (salicylidene-paminobenzoic ac... more Encapsulation of nickel(II) complex of the Schiff base-type ligand (salicylidene-paminobenzoic acid) in the intracrysatalline nano-pores of zeolite-Y is reported. The zeoliteencapsulated trinuclear Ni(II)-Schiff base complex was prepared by diffusion of the ligand through pores of the zeolite, already exchanged with the respective metal (flexible ligand method). The host/guest compound obtained was characterized by elemental analysis, spectroscopic (IR and electronic) studies, surface texture, thermal analysis and powder x-ray diffraction (XRD). The solids were subjected to in situ FT-IR study of adsorbed carbon monoxide. IR and UV-vis as well as XRD data indicate that the chemical stoichiometry of the complex remains intact upon encapsulation and the geometric environment around the metal ions is a distorted tetrahedral. Experimental evidence indicates that the chemisorption of carbon monoxide is indeed catalyzed by the zeolite-encapsulated complex. Sorption of CO results in the appearance of a series of surface carbonyl species: linear Ni II-CO (2198 cm −1), bridged CO (1896 cm −1), C=O derived from acetone-like species (1728 and 1686 cm-1) and physisorbed CO 2 (2351 cm −1). The acetone-like species are stable upon evacuation which can be considered as bound to Lewis acid sites in the zeolite Y. These species are most significant on the zeolite-encapsulated complex than on metal-exchanged zeolite.

Journal of Macromolecular Science, Part A, 2019

Hybrid oligomers composed of polyurethane methacrylate (PUMA) and polyurethane acrylate (PUA) wer... more Hybrid oligomers composed of polyurethane methacrylate (PUMA) and polyurethane acrylate (PUA) were synthesized by poly addition polymerization of polypropylene glycol (PPG 1000), 2,4and 2,6-toluen diisocyanate (TDI 80/20) and 2-hydroxyethyl methacrylate or 2-hydroxyethyl acrylate. Isopropanol was served as the isocyanate blocking agent. The grafting of either PUMA or PUA oligomers to the vinyl acetate monomer was implemented for the first time for improving the properties of the produced PU-co-VAc or (PUP MA or PUP A) terpolymers as new binders for emulsion coating formulations. The synthesized terpolymers were characterized with Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1 H NMR), scanning electron microscope (SEM), gel permeation chromatography (GPC), minimum film forming temperature (MFFT), thermal gravimetric analysis (TGA), Zeta potential and mechanical properties. It has been shown that properties of the terpolymers and their corresponding films were greatly influenced by the grafting of PUMA and PUA at a low concentration level (5 wt%). Cured films of PU based vinyl acetate (PUP MA or PUP A) exhibited higher thermal stability and less weight loss compared to the vinyl acetate copolymer (PVAC). The synthesized PUP MA and PUP A terpolymers revealed enhanced efficiency as binders for emulsion paints in comparison to the PVAC copolymer.

Chemical Sciences Journal, 2016

Zeolite Y in the sodium form (NaY) was synthesized using amorphous silica ash derived from waste ... more Zeolite Y in the sodium form (NaY) was synthesized using amorphous silica ash derived from waste rice husks under hydrothermal conditions. Structural characterization of NaY before and after modification with ZnO and ZnS has been done using powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N 2 adsorption-desorption at-196 °C, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The effects of the Na 2 O/SiO 2 and Si/Al ratios, aging temperature and crystallization time on the optimized synthesis of NaY were thoroughly investigated. Thus the regulated Na + impurity concentration in the starting hydrogel was found to act as a template-assisted synthesis of zeolite NaY by the potential incorporation of Al atoms into the zeolite framework. Results of surface analyses indicate that the interactions of ZnO and ZnS with NaY zeolite are distinguishable and thus the higher interaction is observed for the latter. While Zn II has experienced electrostatic bonding interaction with the framework oxygen atoms, creation of mesopores in NaY due to local destruction of the zeolite lattice around the growing ZnS particles was evidenced. Wonderfully, ZnS/NaY exhibited a high performance in prohibiting the growth of Escherichia coli (E. coli) and negligible from P. Aeruginosa, and these important features make it a potential candidate as an antimicrobial agent for controlling implant-related infections.

Colloids and Surfaces a Physicochemical and Engineering Aspects, Jul 30, 2002

Science China Materials, 2015

functional performance of the different kinds of zeolites, many studies have been devoted to impr... more functional performance of the different kinds of zeolites, many studies have been devoted to improving synthetic approaches to control crystal size, the size of the intracrystalline pore/channel system and morphology of zeolites [5,6]. Among various types of zeolites, NaP (Na 6 [(AlO 2) 6 (SiO 2) 10 ]⋅15H 2 O) is one of the most interesting structured zeolite with two sets of intersecting channels: 0.31 nm × 0.44 nm and 0.26 nm × 0.49 nm. According to International Zeolite Association (IZA), this structure is called "Gismondine" (GIS) framework topology [7,8]. NaP zeolite offers the greatest promise for gas separation applications due to its small pore size [9,10], and is also useful for removal of toxic and radioactive waste species like Cs, Sr, Ba, Pb, U, heavy metals, and ammonium from wastewater, seawater potassium extraction and formation of environmental friendly detergent [11,12]. NaP zeolite can be synthesized from various precursor materials and various methods. It can be synthesized from: (i) clay at a crystallization temperature of 85ºC [13], (ii) sodium silicate solution [14], and (iii) high silicon fly ash of coal combustion at 120ºC for 4 h [15]. Among them the most common methods used for the synthesis of NaP zeolite are the sol-gel technique, hydrothermal synthesis and microwave heating synthesis [1]. The NaP zeolite with different morphologies can offer many intriguing properties: places to store the guest molecules and to perform chemical reactions with selected-sized molecules. Thus, the NaP zeolite morphology and its important correlation with properties is the need of the recent research. In this work, we attempted the template free hydrothermal synthesis of NaP under controlled conditions. Based on multiple paths that can be involved in the hydrothermal synthesis of NaP, optimization of crystallization conditions was adapted through variation of the following parameters: Na 2 O/SiO 2 and SiO 2 /Al 2 O 3 molar ratios, aging time and aging temperature. The characteristics of the synthesized gels NaP zeolite particles were prepared through a template-free hydrothermal condition at 100ºC. Parameters like Na2O/SiO2 and SiO2/Al2O3 molar ratios, gel aging time and aging temperature were investigated for regulating the crystallization of the final product. The samples at different synthesis stages were characterized with N2 adsorption at −196ºC, field emission scanning electron microscopy (FE-SEM), temperature programmed desorption of ammonia adsorption, X-ray diffraction, thermogravimetric and differential scanning calorimetry analysis and Fourier transform infrared spectroscopy. The experimental results evidenced that a high ordering crystallinity of NaP zeolite was obtained at Na2O/SiO2 and SiO2/Al2O3 molar ratios of 1.10 and 1.40, respectively, and a temperature of 100°C for 4 days of aging. FE-SEM image exhibited polycrystalline aggregates of NaP zeolite with crystallite sizes ranging up to 5.04 μm with cactus/cabbage like structures. The quantitative analysis of the total number of acid sites was found to increase as Na2O increases. The NaP zeolite sample with a Na2O/SiO2 molar ratio of 1.13 exhibited a large fraction of the acid sites on its external surface, contrary to that synthesized with a relevant ratio of 1.10. The optimized NaP zeolite could be successfully bestowed with excellent sorption properties of Ca(II) in aqueous solution. The kinetic parameters for Ca(II) adsorption were thoroughly investigated.

Applied Catalysis B: Environmental, 2016

Highly stable and magnetically recoverable MFe 2 O 4 (M= Zn, Co, Mn) spinel ferrite nanoparticles... more Highly stable and magnetically recoverable MFe 2 O 4 (M= Zn, Co, Mn) spinel ferrite nanoparticles; synthesized using sol gel-hydrothermal technology via utilizing polyvinyl alcohol surfactant, were proposed as heterogeneous catalysts for the reduction of nitroarenes. The morphological characteristics, structural exploration, surface, optical, and vibrational properties were performed using powder X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive X-ray, N 2 sorptiometry, diffused UV-visible reflectance spectroscopy. The results showed that MnFe 2 O 4 exhibited the best performance in the reduction of 4-nitrophenol (4-NP), 2,4,6 tri-nitrophenol (2,4,6-NP) and 4-nitroaniline (4-NA) and revealed 100% conversion into the corresponding amino derivatives in 270 sec with rate constant equal 0.01061 sec-1 , 0.01134 sec-1 and 0.01355 sec-1 , respectively. The superiority of the catalytic reduction of MnFe 2 O 4 was due to increasing the pore radius and pore volume (6.75 nm, 0.227 cc/g) values compared to other nanoferrites. The synthesized nanoferrites indicate independence of the activity on crystallite sizes due to the insignificant margin of change (from 6 to10 nm). Conversely, decreasing the activity of ZnFe 2 O 4 was due to increasing the Zn 2+ ions size that induces an increase in lattice parameter values and thus increases the long-range electron transfer between Fe 2+-Fe 3+ ions. The MnFe 2 O 4 catalyst that presented the highest saturation magnetization (135 emu/g) indicated the highest reduction potential for 4-NA comparatively in the presence of NaBH 4 and the reduction reaction followed pseudo first-order kinetics. Increasing the reduction performance of 4-NA compared to other nitroaromatics on MnFe 2 O 4 was explained based on the formed intermediates, their reactivities, and hydrophobicites.

Environmental Technology & Innovation, 2015

ABSTRACT Rice husk was chemically modified with synthesized hexadecylpyridinium bromide (HDPBr) t... more ABSTRACT Rice husk was chemically modified with synthesized hexadecylpyridinium bromide (HDPBr) to enhance Cr(VI) adsorption capacity of the obtained surfactant modified rice husk (HDP+/RH). The structure of as-synthesized HDPBr surfactant was confirmed with 1H NMR spectroscopy. The interaction between the HDPBr molecules and the RH surface was investigated by X-ray diffraction (XRD), FTIR spectroscopy, scanning electron microscopy (SEM) and nitrogen adsorption at −196 °C. HDP+/RH brought about decrease in the values of specific surface area, pore radius, pore size and pore volume compared with those of pure RH, indicating pore narrowing through grafting of HDPBr on the RH surface. The IR spectrum of HDP+/RH exhibited new frequency peaks at 1614, 1490, 1115 and 1043 cm−1 due to vibration of pyridinium ion, fact that is indicative of the successfully anchoring of the surfactant molecules through hydrophobic bonding to the cellulose chains in RH. The adsorption of Cr(VI)-oxyanions onto RH and HDP+/RH was investigated by batch studies at 20 and 50 mg L−1 initial concentration. HDP+/RH was evaluated as an efficient adsorbent for the Cr(IV)-oxyanions than RH, which rapidly attained equilibrium after 45 min compared with the latter at 110 min. This allows evidence for the electrostatic interaction between the Cr(VI)-oxyanions and HDP+-promoted RH. The adsorption data fitted reasonably with the Langmuir and Freundlich models for HDP+/RH, similarly the pseudo-second-order model shows a better fitting. The intraparticle diffusion analysis suggests that adsorption of Cr(VI) ions by HDP+/RH involved intraparticle diffusion which contributed to the rate of the process.

Journal of Sol-Gel Science and Technology, 2015

Silver nanoparticles embedded in a carboxymethyl cellulose matrix (AgNPs/CMC) were synthesized by... more Silver nanoparticles embedded in a carboxymethyl cellulose matrix (AgNPs/CMC) were synthesized by a UV irradiation technique. The successful formation of AgNPs/CMC was examined using UV-Vis spectroscopy, XPS, XRD, TEM, and FTIR. The factors in the preparation process that affected the final products were extensively studied. Thus, 5.0 mM AgNO 3 , 0.5 g l-1 CMC, and exposure to UV light for 2.5 min provide excellent combinations to accomplish the AgNPs/CMC formation. Measurements of optical spectra showed that the surface plasmon resonance was localized around 426 nm when the reaction mixture exposed to UV light for 0.5 min; that is monotonically blue shifted to 403 nm up to 2.5 min exposure time. This is manifested in a quick reduction of Ag ? into smaller Ag nanoparticles. The IR analysis indicated that hydroxyl and carboxylate groups in CMC were included in coordination with the Ag ? ions through displacement of one proton. Upon absorbing UV light, the cellulose hydroxyl and carboxymethylic groups get excited, which reduce Ag ? ions to Ag nanoparticles. The TEM image for the optimal designed AgNPs/CMC sample confirmed that AgNPs are formed with many individual spherical shapes and an average diameter of 15.5 nm. This AgNPs/CMC sample showed promising antibacterial properties toward E. coli.

Studies in Surface Science and Catalysis, 1997

The role of hydrogen in the selective reduction of NO by CO over Au/NaY catalysts has been discus... more The role of hydrogen in the selective reduction of NO by CO over Au/NaY catalysts has been discussed. The NCO intermediates detected by FT-IR absorption at 423–573 K shows a dependence on the presence of H2 which functions in N-O dissociation. The yields of N2 and CO2 were increased in the presence of hydrogen when NCO complexes were present in the gold catalyst up to 573 K. Above this temperature, where direct NO+CO is the only competing reaction, the presence of hydrogen reduced conversions. The results indicated that dual AuI and AuO sites are effective in maintaining higher activities of gold catalysts for the above reaction. The AuI species gave a characteristic carbonyl IR absorbing band at 2188 cm−1.

J. Chem. Soc., Faraday Trans., 1993

ABSTRACT

Journal of the Chemical Society, Faraday Transactions, 1990

ABSTRACT

ChemInform, 2010

Gold(I) Prepared by Monolayer Dispersion of AuCl3 inside Na-Y Zeolite.-Physically mixed samples o... more Gold(I) Prepared by Monolayer Dispersion of AuCl3 inside Na-Y Zeolite.-Physically mixed samples of Au2Cl6 with partially dehydrated Na-Y zeolite prepared at room temperature under N2 atmosphere are thermally evacuated at 323 K for 72 h. Studies of the structural changes of the Au2Cl6 species show the formation of a crystalline phase due to condensation of Au species on the zeolite surface. The crystalline phase disappears on further heating to 338 K due to vaporizing of the crystals and diffusion of Au2Cl6 vapors into the cages and channels of the zeolite. The migration is associated with a partial reduction of Au(III) to Au(I) ions by formation of (AuCl)n zigzag chains. Au-O interactions at 323 K shown by the EXAFS data result from interactions of Au2Cl6 with traces of H2O in Na-Y.-(SALAMA, T.

Surface Science, 1990

ABSTRACT

Reaction Kinetics & Catalysis Letters, 1992

Platinum catalysts supported on a TiO 2 phase welldispersed on Si02 (Ti02/SiO 2) exhibited a high... more Platinum catalysts supported on a TiO 2 phase welldispersed on Si02 (Ti02/SiO 2) exhibited a high activity for butane hydrogenolysis; activity was I~ 2 orders of magnitude higher than those of platinum catalysts supported on Si02 and TiO 2. KaTaaH3aTop~ Pt, HaHeCeHHNe Ha Ti02, xopomo aMcnepcMpOBaHH~M Ha ca~e Si02 (Ti02/Si02), o6aa~a~r BNCOKOM aKTHBHOCTSD K FMBpoFeHO~M3y 6yTaHa; 9Ta aKTMBHOCTb OKa~8~ZC5 Ha 1 ~ 2 no

Microporous and Mesoporous Materials, 2005

High silica mordenite samples (Si/Al molar ratios 38 and 60) were synthesized hydrothermally at 4... more High silica mordenite samples (Si/Al molar ratios 38 and 60) were synthesized hydrothermally at 433 K with the template route method using o-phenylenediamine and characterized with several techniques including XRD, FT-IR, TG/DTA, pyridine-FTIR and N 2 adsorption. The effects ...

Microporous and Mesoporous Materials, 2006

Copper(II) complex with Schiff base ligand derived from salicyaldehyde and p-aminobenzoic acid wa... more Copper(II) complex with Schiff base ligand derived from salicyaldehyde and p-aminobenzoic acid was encapsulated in the intracrystalline cavities of NaY zeolite via “ship-in-the-bottle” (in situ assembling of the metal complex from smaller moieties) technique. A comparative FT-IR spectroscopic study of CO adsorption on simple Cu ion exchanged zeolite and the encapsulated complex has been carried out. Detailed characterization of the

Microporous and Mesoporous Materials, 2008

Copper(I)-salen: N,N À-ethylenebis(salicylidene-iminato)copper(I), immobilized into the structure... more Copper(I)-salen: N,N À-ethylenebis(salicylidene-iminato)copper(I), immobilized into the structure of Al-MCM-41 has been synthesized by a liquid-phase adsorption of salen through Cu(I)-exchanged Al-MCM-41 (Cu(I)-salen/M imp) and by a flexible ligand method (Cu(I)-salen/M ss). The ligand and complex were characterized by various physico-chemical measurements such as elemental analysis, powder XRD, mid-spectral FT-IR, thermal analysis (TGA, DTGA), surface texture and scanning electron microscopy (SEM). A comparative in situ FT-IR study of CO adsorption onto simple Cu(I)-exchanged Al-MCM-41 and the complex-immobilized Al-MCM-41 has been carried out. The structure of Al-MCM-41 after modification remains intact, which was evident from XRD and FT-IR studies. The surface characteristics and thermal analysis have provided evidence for successful immobilization of the copper complex inside Al-MCM-41. The structure of Cu(I)-salen complex in Al-MCM-41 prepared by the liquid-phase adsorption of salen was more thermally stable than the analogous prepared by the flexible ligand method. The in situ FT-IR investigation of CO adsorption showed a band at 2124 cm À1 due to Cu(I)-CO in the spectrum of Cu(I)-exchanged Al-MCM-41. This band was shifted to 2146 cm À1 in the spectra of Al-MCM-41-containing complex due to a stronger mode of CO interaction. The Cu(I)-salen/M imp sample was more active than the Cu(I)-salen/M ss one in the generation of CO 2 (2336 cm À1), which was produced from CO and H 2 O by the water-gas shift reaction. Surface bound adsorbed species like carbonate (1636, 1590, 1488 and 1434 cm À1) and formate (1727 cm À1) were also detected. The spectrum of the Cu(I)-salen/M ss sample was characterized by a band at 2278 cm À1 assigned to isocyanate ion, NCO À , coordinated to a Cu(I) ion which was absent in the spectra of other samples. The extent of this band depends on the interaction of the immobilized complex with the Al-MCM-41 lattice.

Microporous and Mesoporous Materials, 2006

The interaction between Mo (2–30wt.% expressed as MoO3) and NaY zeolite lattice by applying conve... more The interaction between Mo (2–30wt.% expressed as MoO3) and NaY zeolite lattice by applying conventional impregnation with aqueous (NH4) 6Mo7O24· 4H2O (AHM) and vapor-phase deposition of volatile complex Mo (CO) 6 has been compared. The samples were ...

Microporous and Mesoporous Materials, 2012

Extracted silica and lignin from local rice straw were respectively used as a source of silica an... more Extracted silica and lignin from local rice straw were respectively used as a source of silica and a templating agent for the synthesis of nanosized ZSM-5 zeolite at different aging temperatures with the autoclave process. A comparative analysis between synthesized ZSM-5 with lignin (Z L) and its respective synthesized with most common tetrapropyl-ammonium bromide (TPABr) (Z T) using XRD, FT-IR, TEM, TGA/ DTGA and pore structure analysis by N 2 adsorption at À196°C was conducted. A higher degree of crystallinity and a larger specific surface area (S BET) were presented for Z L at aging temperature of 160 than at 140°C. Concurrently, a decrease in intensity of the diffraction line at d = 3.342 Å A 0 due to a-quartz silica was seen, giving rise to an increase of the dissolution rate of silica component in the gel phase at 160 over 140°C. Complementary TEM and XRD techniques informed that the particle sizes measured 50 and 75 nm for the former and latter, respectively. The Z L surface was modified with TPA + (50-200 mmol) and applied for chromate anions (5-30 ppm) adsorption experiments in the aqueous solution at room temperature and pH 5. The capacity of chromate adsorption over Z L-modified TPA + was greater by threefold than over Z L by the combination of electrostatic effects. The kinetics obeyed Freundlich model where the adsorption onto Z L-modified TPA + affords 3.7 mmol/g.