Aqueous Alkali Solution Research Articles

An investigation of Zr doping in NaBiTi2O6 perovskite by direct hydrothermal synthesis.

The direct crystallisation of perovskites NaBi(Ti(1-x)Zrx)(2)O(6) with x = 0, 0.01, 0.05 and 0.1 at 240 °C is achieved from aqueous alkali (NaOH) solutions of NaBiO(3), TiF(3) and ZrOCl(2). For each material, a single rhombohedral polymorph (R3c a∼ 5.51 Å, c∼ 13.50 Å) can be fitted to powder X-ray diffraction data, with Rietveld refinement showing a linear increase in lattice parameters and unit cell volume with increasing Zr content. Scanning electron microscopy shows micron-sized cube-shaped crystallites for each sample, with energy-dispersive X-ray analysis giving Bi : Ti : Zr ratios consistent with the expected substitution. Raman spectroscopy shows no perturbance of local structure upon Zr doping and the spectrum shows five broad bands, consistent with the literature on similar materials. Attempts to increase the Zr content further (x > 0.1) were unsuccessful by this hydrothermal synthesis method, leading instead to crystalline ZrO(2) by-products. For NaBiTi(2)O(6) and NaBi(Ti(0.99)Zr(0.01))(2)O(6) densified ceramics were prepared (∼95% density of crystallographic value) and their remnant polarisation was found to be reduced upon Zr substitution, along with a higher maximum piezoelectric coefficient, d33, measured and comparable permittivity and dielectric loss to other reported NaBiTi(2)O(6) materials.

Experimental Study on NO Removal Using Non-thermal Plasma Oxidation-alkali Absorption

AbstractA non-thermal plasma oxidation-alkali absorption NO removal system is designed by connecting sequentially an alkali aqueous solution absorption device to a gas discharge reactor. An experimental system of simulated flue gas NO removal using non-thermal plasma oxidation and Ca(OH)

Preparation and properties of novel pH-stable TFC membrane based on organic–inorganic hybrid composite materials for nanofiltration

A series of thin-film composite nanofiltration membranes have been fabricated by coating the poly(vinyl alcohol) and 3-mercaptopropyltriethoxysilane aqueous solution prepared by a sol–gel process on porous polysulfone support, followed by thermal cross-linking treatment. In order to improve the hydrophilicity of the nanofiltration membranes, the –SH in the membranes are oxidized into –SO3H by immersing the membranes in H2O2 aqueous solution. Notably, no organic solvent is used during the membrane preparation, showing enough green chemistry technology for environmental protection. The properties of the composite nanofiltration membranes are characterized by ATR-FTIR, SEM, AFM and static contact angle. The optimal composite nanofiltration membrane (PVA-SMPTES-0.6) developed exhibits a rejection of 98.0% and a water flux of 43.3Lm−2h−1 for a feed containing 2000mgL−1 Na2SO4 at 2.0MPa. Furthermore, no irreversible changes in membrane performance have been observed after prolonged exposure (up to 30 days) of PVA-SMPTES-0.6 membrane to extreme acid or alkali aqueous solution.

Synthesis of some acyclic quaternary ammonium compounds. Alkylation of secondary and tertiary amines in a two-phase system

A series of acyclic symmetrical and asymmetrical quaternary ammonium chlorides of the general formula R1R2R3N+AR4Cl– (R1 = Me, Bu; R2 = n-C12H25, PhCH2, C n H2n+1(OCH2CH2) m , n = 9 and 12, m = 1 and 2; R3 = n-C12H25, PhCH2, HOCH2CH2,–OOCCH2; R4 = n-C12H25, PhCH2; A = (CH2CH2O)1,2, CH2C(O)O) was synthesized by the alkylation of tertiary amines in a two-phase system containing water. A convenient method for the synthesis of the initial symmetrical and asymmetrical tertiary amines of the general formula MeNR1R2 (R1 = Me, Bu; R2 = n-C12H25, PhCH2, CnH2n+1(OCH2CH2) m , n = 9 and 12, m = 1 and 2) in an organic phase-aqueous phase heterogeneous system, which allows the use of aqueous solutions of alkali and amines, was developed. The improved method for the preparation of intermediate ethylene glycol and diethylene glycol monoethers is monoalkylation of glycols in dioxane using solid KOH in a two-phase system.

Ultrasonication-Assisted Hydrothermal Synthesis of Ultralong TiO2 Nanotubes

Abstract Ultralong titanate nanotubes were synthesized by treating general anatase TiO2 in alkaline solution using a facile sonication-assisted hydrothermal method. The as-synthesized products via sonication and sonication-hydrothermal treatment were characterized by SEM, TEM, OM and XRD. The effects of sonication power, sonication frequency and sonication temperature on the morphology and the crystal structure of the products were investigated. The results show that in the range of ultrasonic power (200, 300, 400, 500 W) and frequency (20, 40, 80 kHz), titanium dioxide particles were swelled in alkali aqueous solution to get the hedgehog flocculent intermediate products by ultrasonic irradiation when the ultrasonic temperature was equal or higher than 60 °C; several tens of microns long titanate nanotubes were achieved using the intermediate products as raw materials under the mild hydrothermal conditions of 90 °C and 5 h. The possible formation mechanism for ultralong titanate nanotubes was also discussed. The hedgehog floccules synthesized by sonication play an important role to synthesize the several tens of micrometers long nanotubes.

Physicochemical Properties of Melanin from <em>A. auricula</em> Fruiting Bodies

The physicochemical properties of melanin from <em>Auricularia auricula</em> fruiting bodies were studied. The result showed that A. auricula fruiting bodies melanin powder was dark with a little red and yellow colored (L* = 41.03, a* = 2.26, b* = 3.78). <em>A. auricula</em> fruiting bodies melanin was insoluble in both water and common organic solvents. It dissolved only in alkali aqueous solution and precipitated acidic aqueous solution (pH<3). <em>A. auricula</em> fruiting bodies melanin was gradually oxidative bleached by oxidant and was stable to reducer. It exhibited strong optical absorbance in a wide UV-VIS spectral range. Furthermore, these physicochemical properties were very similar to those of the melanin reported in the previous studies and to those of synthetic melanin. <em>A. auricula</em> fruiting bodies melanin could potentially be used in the food industry as a natural colorant.

Adsorption of polyprotic acid at the water/air interface

A rigorous thermodynamic treatment appropriate for surface adsorption from mixed aqueous solution of alkali and polyprotic acid was derived. Those equations were applied to mixed aqueous solution/air systems of alkali metal hydroxide and FeIII complex with ethylenediamine- N, N, N′,N′-tetraacetate (Fe-EDTA). Surface density of each species arising from Fe-EDTA was separately evaluated, and thus, surface activity of Fe-EDTA was studied, especially its dependence on pH and how it is influenced by the counter cations. Fe-EDTA was positively adsorbed at the water/air interface at very low pHs and negatively at high pHs. The pH range of positive adsorption of Fe-EDTA with potassium ion, as a counter ion, was wider than that with sodium ion. Thus, potassium ion, a structure breaker, tended to smooth surface adsorption of Fe-EDTA at the water/air interface, whereas sodium ion, a structure maker, tended to withdraw Fe-EDTA from the interfacial region.

Hydrolytic Heterocyclization of the 1,1,2,3,3‐Pentacyanopropene Salts

Salts of 5‐amino‐4‐cyano‐3‐dicyanomethylene‐2‐pyrrolinone are formed by action of dilute aqueous solutions of alkalis on pentacyanopropenide‐anion salts. These cyclic salts are transformed to 2,6‐diamino‐3,5‐dicyanoisonicotinates by subsequent action of alkalis.

High-efficiency dye-sensitized solar cells based on ultra-long single crystalline titanium dioxide nanowires

High-efficiency dye-sensitized solar cells (DSCs) based on 3D networks of ultra-long single crystalline TiO2 nanowires are fabricated. By hydrothermal reaction of Ti foils in alkali aqueous solution, following ion exchange and high temperature sintering processes, the ultra-long single crystalline TiO2 nanowires can be prepared. Due to long enough of the TiO2 nanowires, they not only form 1D arrays perpendicular to Ti foils, but also extend to form 3D network structure on the top-side of the arrays. By optimizing the hydrothermal duration at 24 h, the formed TiO2 nanowire membrane based front-side illuminated photoanode shows enhanced dye-loading and light scattering abilities and excellent charge transport properties. So the DSC with this photoanode can attain to the highest power conversion efficiency about 8.05%.

Fabrication of free-standing multilayer films by using pH-responsive microgels as sacrificial layers

A facile way to prepare free-standing polyelectrolyte multilayer films of poly(sodium 4-styrenesulfonate)(PSS)/poly(diallyldimethylammonium)(PDDA) was developed by applying a new pH-dependent sacrificial system based on cross-linked poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) microgels. The tertiary amine groups of PDMAEMA microgels can be protonated in acidic environment, and the protonated microgels were deposited by layer-by-layer (LbL) technique with PSS. PSS/PDDA multilayer films were constructed on the top of the PSS/microgels sacrificial layers. The LbL assembly process was investigated by UV-vis spectroscopy. Further study shows that the free-standing PSS/PDDA multilayer films can be obtained within 3 min by treating the as-prepared films in alkali aqueous solution with a pH of 12.0. The pH-triggered exfoliation of PSS/PDDA multilayer films provides a simple and facile way to prepare LbL assembled free-standing multilayer films.

Dissolution of cellulose in aqueous NaOH/urea solution: role of urea

Urea can improve the solubility and stability of cellulose in aqueous alkali solution, while its role has not come to a conclusion. To reveal the role of urea in solution, NMR was introduced to investigate the interaction between urea and the other components in solution. Results from chemical shifts and longitudinal relaxation times show that: (1) urea has no strong direct interaction with cellulose as well as NaOH; (2) urea does not have much influence on the structural dynamics of water. Urea may play its role through van der Waals force. It may accumulate on the cellulose hydrophobic region to prevent dissolved cellulose molecules from re-gathering. The driving force for the self-assembly of cellulose and urea molecules might be hydrophobic interaction. In the process of cellulose dissolution, OH− breaks the hydrogen bonds, Na+ hydrations stabilize the hydrophilic hydroxyl groups and urea stabilizes the hydrophobic part of cellulose.

Formation of hydrogen from oxidation of Mg, Mg alloys and mixture with Ni, Co, Cu and Fe in aqueous salt solutions

We have investigated the oxidation processes of Mg, Mg alloys with Ni, Co, Cu and powdered mixtures of these metals obtained from mechanical treatment of individual components in orbital mill, in aqueous solutions of alkali and alkaline earth metals. It was demonstrated that nearly stoichiometric amount of hydrogen in respect to Mg can be obtained at production rates of up to 640 mL/g min by oxidation of Mg–Co alloy or mechanically processed Mg–Co powder (“mechanical alloy”) in aqueous solutions of Na or K chlorides. Activator metals are not oxidized during this reaction. It is assumed that Mg oxidation is similar to the electrochemical corrosion process.

Production and characterization of geopolymers based on mixed compositions of metakaolin and coal ashes

Mixtures of coal ashes from pulverized coal combustion (PCC) or fluidized bed combustion (FBC) and metakaolin were used to synthetize geopolymers. Upon full characterization of the raw powders (chemical and mineralogical composition), geopolymerization tests were conducted using an alkali aqueous solution of NaOH/Na2SiO3 at different dilutions. The produced geopolymers were subjected to SEM analysis, as well as to leaching, thermal and mechanical tests. The final microstructure and the properties of the geopolymers indicate that FBC ash can be conveniently used as a partially reactive filler in combination with the metakaolin powder. The composite material has good thermal performance and compressive strength (∼30 MPa) suitable for the building sector.

Growth of titanium oxide or titanate nanostructured thin films on Ti substrates by anodic oxidation in alkali solutions

Anodic oxidation of Ti in aqueous NaOH solutions is employed to grow titanium oxide or titanate nanostructured thin films on Ti substrates. The effect of voltage (10–30V), temperature (20–80°C), NaOH concentration (0.5–4M) and oxidation duration (0.5–5h) on the chemical composition, morphology, and photoelectrochemical property of as-grown films has been investigated. It is found that the film composition is strongly related to the alkali concentration. Titanium oxide films are obtained in low-concentration NaOH solutions (≤2M), whereas the films primarily consist of titanate if the NaOH concentration reaches 4M. Our results have also shown that by changing the growth conditions the films with different morphology can be obtained. When anodizing Ti at 80°C and 30V for 3h, for example, a nanowire film with net-like morphology and a nanoleaf film can be grown in 2M and 4M NaOH solutions, respectively. An analysis of the correlation of measured photocurrent with film thickness or surface roughness reveals that the photoelectrochemical property of the titanium oxide films is dependent on both their thickness and surface morphology. The nanowire film with net-like morphology is found to be more photoactive than other films due to its relatively large thickness (~510nm), high surface roughness (~18.4nm) and one-dimensional structural feature. Based on the experimental results, a possible mechanism for growth of titanium oxide or titanate thin films on Ti substrates in alkali aqueous solutions via anodic oxidation has been proposed.

Influence of alkali treatment on the properties of adsorbents based on naturally oxidized Kuznets Basin coal

The influence of alkali treatment on the properties of adsorbents derived from naturally oxidized Kuznets Basin coal is considered. The alkali used in the research is potassium hydroxide, when the mass ratio of KOH and coal is R KOH = 1.0 g/g. The pore structure is compared for two series of samples obtained by different methods: steeping of the coal with aqueous alkali solution and subsequent drying; and mechanical mixing with solid KOH.

Size sorting of chemically modified graphene nanoplatelets

Size-sorted graphene nanoplatelets are highly desired for fundamental research and technological applications of graphene. Here we show a facile approach for fabricating size-sorted graphene oxide (GO) nanoplatelets by a simple centrifugal method using different dispersion solvents. We found that the small-sized GO nanoplatelets were more effectively separated when dispersed in water or dimethylformamide (DMF) than in an alkali aqueous solution. After several iterations of the centrifugation, the sizes of GO in the supernatant solution were mostly several micrometers. We found that the GO area was not strongly correlated with the C-O content of the GO dispersed in water. However, the size-sorted GO nanoplatelets in DMF showed different C-O content, since DMF can reduce GO nanoplatelets during exfoliation and centrifugation processes.

ChemInform Abstract: Cyclization of Dialkyl(3‐phenylpropen‐2‐yl)‐(3‐phenylpropyn‐2‐yl)ammonium Bromides by the Action of an Aqueous Alkali Solution. Aqueous‐Alkaline Cleavage of the Cyclization Products — N,N‐Dialkyl‐4(9)‐phenyl‐3a,4‐dihydrobenzo[f]isoindolinium Bromides.

ChemInform Abstract: Cyclization of Dialkyl(3‐phenylpropen‐2‐yl)‐(3‐phenylpropyn‐2‐yl)ammonium Bromides by the Action of an Aqueous Alkali Solution. Aqueous‐Alkaline Cleavage of the Cyclization Products — N,N‐Dialkyl‐4(9)‐phenyl‐3a,4‐dihydrobenzo[f]isoindolinium Bromides.

Modification of heavy-oil rheology via alkaline solutions

Hamaca (Orinoco Belt, Venezuela) is considered here as a typical viscous and heavy oil whose rheology and recovery behavior is potentially modified by diluents and aqueous solutions of alkali. Viscosity of dry Hamaca crude oil, mixtures of Hamaca and n-decane, as well as emulsified crude oil was measured ex-situ and in-situ (sand pack) as a function of temperature and shear rate. Hamaca crude oil exhibits temperature-dependent rheological behavior. Between 30 and 50° C, it is slightly shear thinning, whereas from 55 to 80° C, properties are slightly shear-thickening. Shear stress sensitivity becomes greater as shear rate decreases. Crude oil rheological behavior in a sand pack (single-phase flow) has similar trends as bulk crude-oil viscometer measurements. The viscosity of the crude oil decreases most significantly as the concentration of diluent (decane) increases from 0 to 6 wt% but the magnitude of viscosity reduction is less as diluent concentration increases from 10% to 33%. After mixing crude oil with aqueous alkaline silicate and carbonate solutions, viscosity decreases markedly due to formation of oil in water (o/w) emulsions. For sodium hydroxide, however, oil viscosity increases because of formation of water in oil (w/o) emulsions. Given the encouraging changes in bulk oil properties, core flood recovery tests at different temperatures and flow rates were conducted. Alkaline flooding showed recovery of about 43% after 0.5 PV of injection and more than 60% with 5.6 PV of 1 wt% Na2CO3 solution. A significant fraction of the oil recovery occurred as o/w emulsion. The apparent relative permeability of the oil phase deviates markedly from the measurements for unemulsified oil.

The discharge current effect on the electrolyte nonequilibrium mass transfer rate under the action of an atmospheric glow discharge

The mass transfer rates obtained from experiments for aqueous solutions of inorganic acids and alkali are presented. It is shown that the nonequilibrium evaporation rate versus the discharge current characteristic has an S-shaped form. It is suggested that the break area in the current curve corresponds to the change of the mass transfer mechanism.

4-Hydroxy-3-(α-nitroalkyl-ONN-azoxy)furazans and some their O-derivatives

Methods for the synthesis of 4-hydroxy- and 4-alkoxy-3-(a-nitroalkyl-ONN-azoxy)furazans and difurazanyl ethers were developed. The methods involve displacement of the nitro group from 4-nitro-3-(α-nitroalkyl-ONN-azoxy)furazans under the action of aqueous solutions of alkalis, mono- and diatomic alcohols (in the presence of inorganic bases), and sodium carbonate in anhydrous acetonitrile.