Mixture Of Sodium Silicate Research Articles

ADSORPTION OF Ca(II), Pb(II) AND Ag(I) ON SULFONATO-SILICA HYBRID PREPARED FROM RICE HULL ASH

In this research, adsorption of Ca(II), Pb(II) and Ag(I) in aqueous solution onto sulfonato-silica hybrid (SSH) prepared from rice hull ash (RHA) has been studied. The preparation of SSH adsorbent was carried out by oxidation of mercapto-silica hybrid (MSH) with hydrogen peroxide (H2O2) solution 33%. MSH was prepared, via sol-gel process, by adding 3 M hydrochloric acid solution to mixture of sodium silicate (Na2SiO3) solution and 3(trimethoxysilyl)-1-propanthiol (MPTS) to reach pH of 7.0. Solution of Na2SiO3 was generated from destruction of RHA with sodium hydroxide solution followed with heating at 500 °C for 30 min. The SSH produced was characterized with Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analyzer, energy dispersive X-ray (EDX) spectroscopy and determination of ion-exchange capacity for sodium ion (Na+). The adsorption of Ag(I) and Ca(II) were conducted in a batch system in various concentrations for one hour. The adsorbent ion was calculated based on difference of concentrations before and after adsorption process determined using atomic absorbance spectrophotometric (AAS) method. The adsorption character was evaluated using model of isotherm Langmuir and Freundlich adsorption to calculate the capacity, constants and energy of adsorption. Result of characterization by EDX and FTIR showed qualitatively that SSH has been successfully synthesized which were indicated by appearance of characteristic absorbance of functional group namely silanol (Si-OH), siloxane (Si-O-Si), methylene (-CH2-) and disappearance of mercapto group (SH). The XRD data showed amorphous structure of SSH, similar to silica gel (SG) and MSH. The study of adsorption thermodynamics showed that oxidation of MSH into SSH increases the ion-exchange capacity for Na+ from 0.123 to 0.575 mmol/g. The change in functional group from silanol to mercapto and from mercapto to sulfonato increases the adsorption capacity of Ca(II). However, the capacity order of adsorbents for both ions of Pb(II) and Ag(I) in aqueous solution is MSH > SG > SSH.

Ultra-low-cost route to mesocellular siliceous foam from steel slag and mesocellular carbon foam as catalyst support in fuel cell

A large- and uniform-pore-sized mesocellular siliceous foam with a high surface area is successfully synthesized, using blast-furnace slag as an ultra-low-cost silica source, under neutral pH conditions. A high-purity silica source can be easily prepared from blast-furnace slag by extraction using an acid leaching process, followed by dissolution in NaOH solution. The mesocellular siliceous foam is synthesized by the interaction of these silicate precursors with P123 ((EO) 20(PO) 70(EO) 20) block copolymers in the presence of trimethylbenzene (TMB) used as a pore expander, followed by calcination at 550 °C in air. The resulting mesocellular siliceous foam denoted as MSU-F–SP has ∼30 nm sized large pores and high BET surface area of 554 m 2 g −1. The structure of MSU-F–SP is very similar to MSU-F silica synthesized from sodium silicate mixtures in the presence of P123 and TMB. Mesocellular carbon foam is easily synthesized through the direct carbonization of a tri-block copolymer in the as-synthesized mesostructured materials after acid-catalyzed polymerization using sulfuric acid. The sulfuric acid is used as a dehydration catalyst and the amount of sulfuric acid is controlled to optimize the pore structure. The mesocellular carbon foam synthesized using 0.16 mL of sulfuric acid per gram of composite material has the most uniform pore structures. A mesocellular carbon foam with high surface area and large mesopores allows good dispersion of Pt nanoparticles, leading to a higher methanol electro-oxidation activity in fuel cells compared to that of Pt nanoparticles on Vulcan XC-72.

EFFECT OF AGING TIME TOWARD CRYSTALLINITY OF PRODUCTS IN SYNTHESIS OF MESOPOROUS SILICATES MCM-41

Researches about the effects of aging time toward crystallinity of products in the synthesis of mesoporous silicates MCM-41 have been done. MCM-41 was synthesized by hydrothermal treatment to the mixture of sodium silicate, sodium hydroxide, cetyltrimetylammoniumbromide (CTMAB) and aquadest in the molar ratio of 8Na2SiO3 : CTMAB : NaOH : 400H2O. Hydrothermal treatment was carried out at 110 °C in a teflon-lined stainless steel autoclave heated in the oven, with variation of aging time, i.e.: 4, 8, 12, 16, 24, 36, 48, and 72 h respectively. The solid phase were filtered, then washed with deionised water, and dried in the oven at 100 °C for 2 h. The surfactant CTMAB was removed by calcinations at 550 °C for 10 h with heating rate 2 °C/min. The as-synthesized and calcined powders were characterized by using FTIR spectroscopy and X-ray diffraction method. The relative crystallinity of products was evaluated based on the intensity of d100 peaks. The best product was characterized by using N2 physisorption method in order to determine the specific surface area, mean pore diameter, lattice parameter, and pore walls thickness. It was concluded that the relative crystallinity of the products was sensitively influenced by the aging time. The highest relative crystallinity was achieved when used 36 h of aging time in hydrothermal treatment. In this optimum condition the product has 946.607 m2g-1 of specific surface area, 3.357 nm of mean pore diameter, 4.533 nm of lattice parameter, and 1.176 nm of pore walls thickness.

Microstructure Study of Early In Situ Reaction of Fly Ash Geopolymer Observed by Environmental Scanning Electron Microscopy (ESEM)

The alkali activation of waste materials can produce a binder with similar properties as Portland cement but without the drawback linked to greenhouse gas emissions. Geopolymer pastes were made using coal fly ash as precursor and sodium hydroxide and solid sodium silicate powder as alkaline activators. One sample was activated with sodium silicate only while the second sample used a 50:50 mass% mixture of sodium silicate and 8 M NaOH solution. Fresh geopolymer paste was immediately placed in the Environmental SEM chamber for microstructure observation using the ESEM mode. The sodium silicate activator dissolves rapidly and begins to bond fly ash particles. Open porosity can be observed and is rapidly filled with gel as soon as the liquid phase is able to reach the ash particle. The liquid phase is important as a fluid transport medium permitting the activator to reach and react with the fly ash particles. During this ESEM experiment, the reaction was limited to the surface of the fly ash particles. The reaction products examined had a gel like morphology and no crystallized phase was observed. The effect of the activator on the gel composition was investigated by quantitative microanalysis. The gel analyzed in the sample activated with the mixture of sodium silicate and NaOH solution is enriched in Na and Al. In that sample, the fly ash reaction rate is more advanced considering that the gel is richer in Al and that this element results from the fly ash. In fly ash-based geopolymers, the aluminum content of the aluminosilicate gel is an indicator of the fly ash reactivity.

SYNTHESIS AND CHARACTERIZATION OF MESOPOROUS ALUMINOSILICATES Al-MCM-41 AND INVESTIGATION OF ITS THERMAL, HYDROTHERMAL AND ACIDITY STABILITY

The synthesis and characterization of mesoporous aluminosilicates Al-MCM-41 and the investigation of its thermal, hydrothermal and acidity stability have been done. Al-MCM-41 were synthesized by hydrothermal method to the mixture of sodium silicate as Si source, aluminium hydroxide as Al source, sodium hydroxide as a solvent, and cethyltrimethylammoniumbromide (CTAB) as structure directing agent. The reaction were carried out in alkaline condition (pH = 10.2) at 383 K for about 24 h, followed by calcination at 723 K for about 10 h. The synthesized crystals were characterized using FTIR spectroscopy, X-ray diffraction and N2 fisisorption methods. The result showed that Al-MCM-41 sample with hexagonal structure was formed, it has a good in thermal and acid stability, but the structure disintegrated in an alkaline solution (pH = 10) and in boiled water. Keywords: synthesis, characterization, Al-MCM-41, stability

Mesoporous titanosilicates with high loading of titanium synthesized in mild acidic buffer solution

Mesoporous titanosilicates with high titanium content were synthesized under mild acidic conditions (pH = 4.4, HAc–NaAc buffer solution) by co-condensation of acetylacetone-modified titanium isopropoxide (Ti(OBu n ) 3 (acac)) and mixture of sodium silicate with tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS) or tetrakis(2-hydroxyethyl)orthosilicate (EGMS), using block copolymer Pluronic P123 as template. The combined results of XRD, N 2 sorption and TEM show that the highly regular structure of the mesoporous titanosilicates can still be obtained when Ti/Si molar ratio in the final product is as high as 0.059. The results of UV–vis diffuse reflectance spectra and UV resonance Raman spectra show that the framework titanium species are predominant in the mesoporous titanosilicates when Ti/Si molar ratio in the final product is less than 0.042. The mixture of sodium silicate and EGMS was proved to be the best silicon source for the synthesis of titanosilicates with ordered mesostructure and high titanium content. The efficiency of this synthetic method may be attributed to the mild acidic medium as well as the modified hydrolysis–condensation rate and hydrophility of the precursors.

Pore size control of mesoporous silicas from mixtures of sodium silicate and TEOS

Mesoporous silicas with large and tunable pore size (10–16 nm) were successfully synthesized from mixtures of sodium silicate (Na2SiO3) and tetraethoxysilane (TEOS) in acetic acid/sodium acetate buffer solution (pH 4.4, HAc–NaAc) using poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (EO20PO70EO20, denoted as P123) as template, in which TEOS acts both as a swelling agent and a silica source. Highly ordered 2-D hexagonal and mesostructured cellular foam structure with large pore size could be obtained using sodium silicate and TEOS as silica source, respectively. By adjusting the initial molar ratio of TEOS/(Na2SiO3+TEOS) from 0 to 0.5, the pore sizes of the final ordered 2-D hexagonal mesoporous silicas could be precisely tuned from 10 to 15 nm. The large pore size (15 nm) of the material was attributed to the slow hydrolysis and polymerization rate of TEOS in the buffer solution. The presence of ethanol in the synthesis system also has strong effects on the mesostructure and pore size of the materials. 2007 Elsevier Inc. All rights reserved.

The effects of some polyelectrolyte chemical compositions on the rheological behaviour of kaolin suspensions

Many ceramic materials are factory-made via ceramic suspensions. The rheology of these suspensions must be appropriate and their solid content must be as high as possible in order to minimize the drying cost. Currently, the addition of minor quantities of polyelectrolyte in the classical deflocculating mixture of sodium silicate and sodium tripolyphosphate has become useful to this effect. The present paper discusses a rheological test established to put the rheological behaviour of these suspensions in parametric form. These parameters cover different rheological aspects: equilibrium, kinetics (thixotropy) and structural elasticity. Different polyelectrolytes in different percentages were tested for their power to deflocculate different kaolin suspensions. The deflocculating power of these polyelectrolytes was then correlated with their chemical composition.

Catalytic activities of nickel-containing catalysts for ethylene dimerization and butene isomerization and their relationship to acidic properties

Nickel oxide-silica catalysts were prepared by precipitation from an acidic solution of a nickel salt–sodium silicate mixture. Two types of nickel hydrosilicate, montmorillonite and antigorite are formed in the catalysts. Catalytic activities of nickel silicates for ethylene dimerization and butene isomerization run parallel when the catalysts are activated by evacuation at elevated temperatures, giving two maxima in activities. The variations in catalytic activities are closely correlated to the acidity of catalysts. The acid site responsible for the catalytic activity is protonic on montmorillonite, while non-protonic on antigorite, as evidenced by the effect of water content and the IR spectra of adsorbed pyridine. Catalytic activities of NiO-TiO 2 catalysts modified with H 2SO 4, H 3PO 4, H 3BO 3 and H 2SeO 4 for ethylene dimerization and butene isomerization were examined. The order of catalytic activities for both reactions was found to be NiO-TiO2/SO 4 2−⪢NiO-TiO 2/PO 4 3−>NiO-TiO 2/BO 3 3−>NiO-TiO 2/SeO 4 2−>NiO-TiO 2, showing clear dependence of catalytic activity upon acid strength. Catalytic activity of nickel sulfate supported on γ-Al 2O 3 (NiSO 4/γ-Al 2O 3) for ethylene dimerization is also closely correlated to the acidity of catalysts, showing that the active sites consist of a low-valent nickel (Ni +) and an acid.

Synthesis of gallosilicates — MTW- type structure zeolites: Evidence of Ga-substituted T atoms

Gallosilicates with the ZSM-12 structure have been synthesized from the reaction mixture of sodium silicate, gallium nitrate, and methyl triethylammonium bromide at 353 K in an autoclave. XRD results associated with an i.r. study of the lattice vibrations indicated that highly crystalline materials with the ZSM-12 structure were obtained. 71Ga MAS n.m.r. studies along with 29Si measurements showed that Ga is in tetrahedral positions and the Si/Ga atomic ratio = 70. T.p.d. of ammonia adsorbed on H-GaZSM-12 clearly showed the acid nature of the material, which supports strongly the presence of Ga 3+ in the zeolite framework.

Solidification of “Cement-Glass”

Cement-glass, which is a mixture of sodium silicate (kNa2O·mSiO2nH2O), silicon phosphate (P2O5·2SiO2) and cement, was developed to solidify radioactive waste pellets in containers. The optimum molar ratio of Si(OH)4, NaOH and P2O52SiO2 was found to be 2:2:1, based on compressive strength measurement of solidified samples. The compressive strength of solidified sodium silicate with silicon phosphate was increased when the amount of solidified SiO2 per unit volume was increased by reducing the water content. Cement-glass had a higher Cs distribution factor than ordinary Portland cement.

Solidification of "cement-glass".

Cement-glass, which is a mixture of sodium silicate (kNa2O·mSiO2nH2O), silicon phosphate (P2O5·2SiO2) and cement, was developed to solidify radioactive waste pellets in containers. The optimum molar ratio of Si(OH)4, NaOH and P2O52SiO2 was found to be 2:2:1, based on compressive strength measurement of solidified samples. The compressive strength of solidified sodium silicate with silicon phosphate was increased when the amount of solidified SiO2 per unit volume was increased by reducing the water content. Cement-glass had a higher Cs distribution factor than ordinary Portland cement.

Stability of Cement-Glass Packages Containing Sodium Borate Salt Generated from Pressurized Water Reactor Power Plants

A new solidification technique using cement-glass, which is a mixture of sodium silicate and cement, was studied for solidification of sodium borate salt of liquid waste generated from pressurized water reactor plants. When the sodium borate salt was solidified with the cement-glass, the resulting package contained eight times more sodium borate than was found in cement because it did not interact with sodium borate. The leaching ratio of cesium ion from the cement-glass package was one-tenth that of cement. Its low leaching ratio was due to the high cesium adsorption ability of cement-glass. The ratio could be theoretically evaluated by considering the cesium adsorption-desorption equilibrium.

Effect of glass, rice-husk ash and wollastonite on transverse strength of porcelain

In o rde r to reduce energy consumpt ion , a t t empts are now being made at add ing at t i t ives to ceramics. In the previous studies we have observed tha t add i t i on o f a small percentage o f addi t ivies such as glass, r ice-husk ash and wol las toni te to porce la in can reduce the firing t empera tu re of the t r iaxial body to a grea t extent [1, 2]. In this let ter the effect o f add i t ion o f glass, r ice-husk ash and wol las toni te on the s t rength and bond ing o f porce la in has been observed. A t t e m p t s have been made to app ly the Spr igg 's equa t ion for the s t rength o f such compos i tes and s t r e n g t h d e n s i t y dependence is observed. The fracture surfaces o f these composi t ies have been observed by scanning e lec t ron microscopy . China clay, flint, ball clay, waste glass powder and wol las toni te were ob t a ined f rom different sources and their chemical analysis was pe r fo rmed using the wet chemical analysis m e t h o d (Table I). Rice husk ash was p repa red by firing washed rice husk. R a w mate r ia l s were separa te ly g r o u n d to pass t h rough a 200 mesh B.S. Sieve. The conven t iona l porce la in mix (china clay 50%, fe ldspar 25% and flint 25%) was taken as the base mater ia l . Different po r t ions o f r ice-husk ash, glass and wol las ton i te were a d d e d to the porce la in (Table II) . The specimens were p repa red in the form o f rods by slip cast ing, using p las ter o f par is moulds . To ob t a in the p rope r consis tency o f the slip, a small quan t i t y o f e lectrolyte (1 :1 ra t io sod ium ca rbona t e and sod ium silicate mixture) was found essential in each case, bu t the a m o u n t var ied with the compos i t i on o f the body . The specimens were dr ied at 110 ° C for 48 h and were fixed at different t empera tu res between 1000 and 1200 ° C in

Leaching Studies of Cement-Glass Package Containing Sodium Borate

AbstractA new solidification technique using cement-glass, which is a mixture of sodium silicate, cement, additives, and initiator of the solidification reaction, was developed for sodium borate liquid waste generated from pressurized water reactor (PWR) plants. The cement-glass could solidify eight times as much sodium borate as cement could, because the solidifying reaction of the cement-glass is not hindered by borate ions.The reaction mechanism of sodium silicate and phosphoric silicate (initiator), the main components of cement-glass, was studied through X-ray diffraction and compressive strength measurements. It was found that three- dimensionally bonded silicon dioxide was produced by polymerization of the two silicates. The leaching ratio of cesium from the cement-glass package was one-tenth that of the cement one. This low value was attributed to a high cesium adsorption ability of the cement-glass and it could be theoretically predicted accordingly.