Preparation and Characterization of Bi2-O3-M2o5 (M =P,As, V) Oxide Ion Conductors

Bi203-M205, M = P, AS, V systems and related materials were prepared by solid state reactions. The phase purity of the materials was determined by X-ray diffraction (XRD). Further characterization using ac impedance spectroscopy and differential thermal analysis (DTA) were carried out on single phase materials. Besides, inductively coupled plasma-atomic emission spectrometry (ICP-AES), density measurement, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Fourier-transform i n h e d (FT-IR) spectroscopy and Rarnan spectroscopy were also performed on selected materials. The crystal system and space group of the single phase materials were determined. Two narrow solid solution series were formed in xBi2O3-P205: 5.5 I x I 6 and 7 I x 5 7.25. In DTA study, a phase transition was clearly seen in Bi7P013 and Bi~gP40~a~t .-856 0°C.XRD shows that single phase materials were formed in xBi203-As205 binary system when x = 5, 5.5, 5.667, 5.75, 6 and 7. Among these, materials in the composition range of 5 5 x 5 6.25 appeared to be solid solutions. Attempts to synthesize materials of composition of xBi203-As2051, I x I 4 were unsuccesshl. Single phase materials were formed in xBi203-V205 binary system, 5 I x I 6 and x = 7. A phase transition was observed in Bi17V303a3n d Bi23V404.5 at -180°C. However, its origin is unknown. Materials of composition xBi203-M205, 5.5 I x I 6 (M = P) and 5 I x I 6 (M = As, V) are refined in triclinic symmetry with space group of P-I. Meanwhile, monoclinic symmetry was found in materials where x = 7, 7.25 (M = P) and x = 7(M = As, V). The XRD and IR patterns of both series of xBi203-As205, 5 I x I 6.25 and xBi203-V205, 5.5 5 x I 6 solid solutions are very similar since these materials are isostructural. Generally, lattice parameters, volumes and densities of the materials in xBi203-M205 system, M = P, As, V increased with the increase of Bi content. A complete solid solution series was formed in the Bi22P4043-Bi22As4043, Bi22P4043- Bi22V4043, Bi22As4043-Bi22V4043, Bi23P40~.5-Bi23As4044.5, Bi23P404.5-Bi23V4044.5, Bi23A~4044.5-Bi23V4044B.5i1, 2P2023-Bi 12A~2023, Bi 12P2023-Bi12V2023, Bi12As20~- Bi12V202a3n d Bi7AsO13-Bi7V013s ystems. In Bi7PO13-Bi7AsO1a3n d Bi7PO13-Bi7V013 systems a two-phase region was seen. All the single phase materials studied above appeared to be oxide-ion conductors. Conductivity increased with increasing vanadium content, followed by arsenic and phosphorus. Among the materials prepared, the highest conductivity is obtained in Bi23V4044.5w ith a 0 value of 1.34 x lo4 ohm" cm" at 300°C. In an attempt to optimize oxide ion conductivity, chemical doping using PbO, S@O3)2, A1203, Ga203, La203, Fe203 etc. was carried out in selected materials, resulting in the formation of limited solid solutions. These materials, however, exhibit conductivity slightly lower than that of the parent materials. Ball milling process has been carried out in the preparation of Bi23V4044.5a nd Bi14P06 in addition to manual grinding prior to fihg of the samples. In ball milling process, high-density, fine-grained powders with uniform grain-size distribution were obtained, resulting in an increase in conductivity and dielectric constants. Sillenite compounds in the Bi203-P205b inary system with Bi:P ratios of 13:l to 16:1 have been synthesized and found to be solid solutions. Substitution of P by V and As in the material where Bi:P = 14:l results in partial and complete solid solutions, respectively. Enhancement in conductivity was observed in these solid solutions with Vdoped materials exhibiting the highest conductivity. Substitution of P by elements such as pb2+, s?+,~ 1 ~~+a,~ ~+e,~ si+4+,,~ e ~an+d ,~ ile~ads +to f ormation of limited solid solutions. Most of these materials have conductivity similar to or slightly higher than that of the parent compound. These materials appeared to be predominantly oxide ion conductors especially at temperatures above 800°C where y + 6' polymorphic transformation occurred

Nanostructured bimettalic oxide modified silica as oxidative-acidic bifunctional catalysts for alikene epoxidation

This project focuses on synthes is of nanostructured bimetallic oxide modified silica as bifunctional catalysts. Silica gel which possesses large surface area will be synthesized via sol-qel method, It will be used as support of the designed catalysts. Bimeta llic oxides will be introduced into/onto silica via impregnation method. Ratio of the bimeta llic oxides to silica will be varied in the synthes is process. All the synth esized materials will be characterized and the ir catalytic activity will be evaluated through epoxidat ion reaction. Lastly. the structurakatalytic act ivity relationship of the prepared materials will be investigated. The role of bimetall ic oxides and their interaction with silica in formation of acidity in the catalyst will also be explored . It will contribute to the basic understanding of th e effect physico-chemica l prope rties such as parti cle size, functional groups. surface area , porosity , surface morphology to th e response cata lytic activity. The fundamental knowledge acquired will lead to novel nanostructured bifunctional catalyst in epoxidation reaction. With better unders ta nding of physic-chemical interaction among niobium. phosphate , titanium and silica, the degree of control in response can be increased. which eventually leads to bifunctional catalyst of improved catalytic performance and subsequently contributes to th e development of an excellent cata lyst in fine chemical indust ry. Recently, high surface area nanostruetured vanadium-phosphate modified silica-titan ia was reported as potential bifunctiona l cata lyst in epoxidation. The inte raction of vanadium-phosphate was crucia l for the formation of Bronsted acidity, while both vanadium titanium species played importa nt as oxidative sites. leading to an excellent bifunctional catalytic performance in alkene epoxidation reaction. Thus, it leads to an intensive research on synthesis of nanostructured bifunctional catalyst of bimetall ic oxides modified silica. The resu lted nanostructured materials could be excellent bifunctiona l cata lysts in alkene epoxidation reaction

Oxidative-acidic bifunctional catalyst of niobium-phosphate-titania supported on silica in production of diols

Niobium-phosphatetitania supported on silica as oxidative-acidic bifunctional catalyst has been synthesized via sol-gel and impregnation methods in different sequences n"r"]y, (i) TiO2, l\brO, and POa3-impregnated stepwise onto silica (P/Nb/T.i/Si), (ii) mixture of TiO2 and Nb2O5 ffleonateo onto silica, f9]l_owed by impregnation of eoo]1e71Nu+Ti)/Si), ano liiii Nb2o5 and PO+" Impregnated onto TiO2-SiO2 (P/Nb/Ti-Si). The results indicated the diffeient properties resulted from varied jnteractions among SiO2 support, TiO2 catalyst and its modifiers have greatly affected the bifunctional catalytic behavior of the synth-esized materials. The XRD results showed an identified peak of titanium oxide in sample P/Nbffi/Si. Meanwhile, samptes P/(Nb+Ti)/Si and P/Nb/Ti-Si were in amorphous form indicating that Ti and Nb were dispeised well on the surface of silica. UV-Vis DR results revealed that oitaheoral or polymeric Ti species was the dominant species in sample P/Nb/Ti/Si while hydrated tetrahedrri Ti rp""ies was predominant in samples P/(Nb+Ti)/Si and P/Nb/Ti-Si. Besides of tetrahedrallv coordinated Ti species, it has been demonstrated that the presence of Nb, POa3- as well as ifr" SiO, support has contributg_d significantly in improving the oxidative catalytic activity. Meanwhile, interaction between PO4"- groups and Nb has generated Bronsted acidity for the high yield of diol. lt has been shown that P/Nb/Ti-Si was the best bifunctional oxidaiive-acidic 6atilystin consecutive transformation of 1-octene to 1,2-octanediol through formation of 1,2-epoxyoctane using aqueous H2O2at 343 K.lt was expected that synthetic method used in preparation of p/Nb/Ti-Si has aided the effective interaction between POa3- and Nb, leading to foimaiion of more Bronsted acidity in this sample

Photodegradation of Malachite Green by Immobilization of Titanium Dioxide on Glass Plates

The effects of pH, contact time, initial dye concentration, numbers of dip coating, light sources and repetitive usage of dip-coated TiO2 were studied in batch experiments in order to investigate the photodegradation efficiency of malachite green in aqueous solution by using titanium dioxide, TiO2 immobilized on glass plates. The photodegradation of malachite green was found to be more effective at lower initial dye concentration. Kinetic studies showed good correlation coefficient for a pseudo-first order kinetic model. The removal of malachite green was dependent on the TiO2 loading where the percentage removal of malachite green was 92.15, 94.28 and 98.43 % for 5, 10 and 15 number of TiO2 dip-coating, respectively. Among the three light sources used, sunlight possessed the highest removal efficiency with 100 % of removal of dye in 6 h of irradiation. The degradation of malachite green was enhanced in basic solution compared with acidic solution due to the amphoteric property of TiO2. The decolourization efficiency was found to be decreased after each repetitive usage of dip-coated TiO2 glass plates. However, the immobilized TiO2 still displayed a good performance in the removal of malachite green.

Cr doped TiO2 supported on TUD-1 photocatalyst for congo red photodegradation

A series of new visible light driven photocatalysts of 1 mol% Cr doped Ti02 supported on various amount of TUD-1 have been successfully synthesized via sol gel method. XRD analysis revealed that all the Cr-Ti02/x TUD-l (x = 10,20,30,40 and 50 mol%) photocatalysts were in amorphous form. Both Ti02 and Cr were incorporated in the highly porous siliceous matrix. FTIR analysis indicated the existence of Si-O-Ti bonding in all the materials. UV-Vis D R analysis suggested that alteration of Ti species occurred from tetrahedrally to octahedrally coordinated Ti species when higher TUD-1 amount was used as photocatalyst support. However, the amount of TUD-1 did not affect the wavelength response and the band gap energy of the resulted materials. All the materials were having band gap energy of ~2.9 eV. The photocatalytic performance of the synthesized materials was evaluated through the photodegradation of Congo Red under visible light irradiation at 298 K for 5 h. Results showed that all the Cr-TiO2/TU D -1 materials had higher photocatalytic activity compared to Cr-TiO2, Amongst, Cr-TiO2/30TU D-1 appeared as the most superior photocatalyst that gave the highest percentage of dye degradation

Low Cost Adsorbents for Sustainable Dye Containing-Wastewater Treatment

Dyes are coloured substances that can be applied to various substrates such as textile materials, leather, paper and hair. The usage of dyes has continuously increased in many industries but the removal of this pollutant remains as a problematic issue as they are generally stable to light and oxidizing agents and are resistant to aerobic digestion. This literature review paper provides and lists several low cost adsorbents to serve as an alternative method for dye removal. Adsorption using low cost materials can be viewed as a sustainable treatment process because most of these materials are of naturally occurring, locally available and inexpensive materials. This paper covers an overview of dyes waste treatments for 5 years period, from 2008-2012. Some of the noteworthy adsorbents include agricultural byproducts, industrial waste and natural clay materials. Besides, the combination processes involving adsorption and other methods was also discussed

Characterization of photochemically initiated gold nanoparticles synthesized via incoherent ultraviolet radiation

A modified Turkevich pathway of synthesizing water suspended gold nanoparticles using incoherent ultraviolet radiation as photochemical reaction initiator produced broader absorbance band corresponding to localised surface plasmonresonsnce around 530 nm with average particle size separated into two distinct distributions from 5 nm to 100 nm depending on ultraviolet wavelength. Presence and dynamics of nanoparticle growth was observed with photon correlation spectroscopy where aged colloids produced submicron sized agglomerated particles. Post-synthesis colloidal pH shows gradual degradation of particle stability

Correlation of fluorescence and photocatalytic activity of co-doped Tio2

Co-doped TiO2 (0.5-4 mol%) photocatalysts were synthesized via sol-gel method and their physical and chemical properties were investigated. Addition of Co oxides dopants induced anatase to rutile phase transition and reduced the band gap energy of TiO2. The fluorescence result indicated that the electron-hole recombination rate was reduced with the presence of Co oxides dopant. The best photocatalyst obtained was 3Co-TiO2 which enhanced the photocatalytic activity of TiO2 by 10 folds to 26.6%. The importance of fluorescence properties of Co-doped TiO2 towards its photodegradation of Congo Red was presented

Synthesis and characterization of molybdena and phosphate doped silica-titania oxidative catalyst for epoxidation of styrene

New oxidative catalysts of molybdena and phosphate doped silica-titania (xMo/PO4 3-/ SiO2-TiO2, x = 0, 1, 2, 4 and 5 wt%) have been prepared in this study. Silica-titania was prepared via sol-gel method by using titanium isopropoxide and tetraethyl orthosilicate as precursors of titania and silica, respectively. Sufficient amount of ammonium molybdate tetrahydrate and 0.2 M phosphoric acid were loaded on silica-titania through impregnation method. The XRD results confirmed the amorphous phase of all the samples Mo/PO4 3-/ SiO2-TiO2, indicating well dispersion of Mo, phosphate and Ti on the silica support. DRUV-Vis analysis revealed the existence of both tetrahedral and octahedral Ti species in the samples. The N2 adsorption surface area analysis showed the surface area decreased with the increasing amount of doped molybdenum. The oxidation catalytic behavior of xMo/PO4 3-/SiO2-TiO2 was evaluated through epoxidation of styrene using H2O2 as oxidant. Amongst, 5Mo/PO4 3-/ SiO2- TiO2was the best oxidative catalyst which gave the highest conversion of styrene and the highest yield of styrene oxide

Synthesis of new biopolymer-coated manganese-zinc ferrite nanocomposites via coprecipitation method

Ferrites are important nanomagnetic materials in chemical industry. Due to their high applicability in pharmaceutical and electronic devices fabrication , these materials have been widely .' investigated. Amongst , manganese and zinc doped ferrite (Mn/Zn ferrite) nanocomposites have attracted intensive attraction of the researchers because of their relatively high magnetic properties . However, magnetic behavior and Van der Waals forces existed in the Mn/Zn ferrite nanocomposites have make the materials naturally amalgamate , leading to reducing of magnetic properties and limitation in their application. In this research, Mn/Zn ferrite was synthesized via chemical co-precipitation , a relatively simple and economical method. In order to study the effect of zinc content towards the magnetic activity, the materials MnxZn1-xFez04 ;x= 1.0, 0.8, 0.6, 0.4, 0.2, 0.1 were synthesized at 7SoC and pH 11. The samples were characterized by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) techniques. Results indicated that the prepared MnxZn1-xFez04were crystallined in spinel cubic structure with particle size ranged 10-19 nm. Besides, the doping of Zn ions into ferrite structure resulted in the reduction of both crystallinity and crystallite size. Further characterizations will be carried out using Transmission electron microscopy (TEM), Fourier transforms Infrared (FTIR) spectrophotocopy, and Vibrating Sample Magnetometry (VSM) techniques. In order to prevent formation of agglomerat ion among the nanoparticles , coating of Mn/Zn ferrite magnetic nanoparticles using biopolymer such as poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA) will be done. It is believed that both stability and magnetic properties of the modified ferrites will be enhanced significantly after the biopolymer coating