Chemical preparation of PLZT powder from aqueous solution

A new method for preparing homogeneous lanthanum-modified lead zirconate-titanate (PLZT) powder from aqueous salt solution containing hydrogen peroxide by precipitation is described. Inorganic salts such as zirconium oxychloride and titanium tetrachloride instead of organo-metallic salts can be available as raw materials which attain well reactioned and fine-grained PLZT powder processed by decomposing the dried product at 650°C. PLZT ceramics formed by hot-pressing the powder show considerable improvements in the qualities such as optical transparency and homogeneity.     

Removal of dyes and their mixtures from aqueous solution using liquid emulsion membrane

Extraction of dyes from aqueous solution was studied using liquid emulsion membrane. Study was carried out using two dyes, namely, crystal violet (CV) and methylene blue (MB). Extraction of single component system of each dye and their binary mixture were investigated. Liquid emulsion membrane was formed using n-heptane as membrane phase, sodium hydroxide solution as the internal phase and dye solution as the external phase. Surfactant span 80 was used as the emulsion stabilizer. Effects of concentration of span 80, concentration of NaOH, stirring speed, composition of feed solution and the volume ratio of the oil phase to the aqueous phase (O/A) were studied in detail both for single and binary system. Maximum extraction of MB was found to be 99% and that for CV was about 95% in single component system. In binary mixture, these values were 97% and 90%, respectively.     

Extraction of Co(II) from aqueous solution using emulsion liquid membrane

The extraction equilibrium of Co(II) from thiocyanate medium by CYANEX 923 (mixture of straight chain alkylated phosphine oxides) in cyclohexane was studied. The stoichiometry of the extraction reaction was postulated based on slope analysis method and the extraction constant Kex was calculated. The stripping percentage of Co(II) with sulphuric acid from the loaded CYANEX 923 was found to increase with the increase in acid concentration. The extraction of Co(II) from aqueous thiocyanate medium into emulsion liquid membrane using CYANEX 923 extractant was also studied. The influence of different parameters such as stirring speed, surfactant concentration, pH of the extractant phase, carrier concentration, internal phase stripping acid concentration, initial Co(II) concentration as well as temperature on the emulsion stability were investigated. The applicability of the emulsion liquid membrane (ELM) process using CYANEX 923 as extractant and SPAN 80 as surfactant for the removal and the concentration of Co(II) from thiocyanate solution was investigated. The results show that it is possible to recover 95% of cobalt in the inner phase after 10 min of contacting time with a concentration factor of 5.     

Effects on engineering properties of cement-treated road base with slow setting bitumen emulsion

This study investigated the effects of the type and amount of Portland cement and cationic slow setting bitumen emulsion additives on the short- and long-term performance of road-based properties using laboratory mechanistic evaluation. Stabilised specimens with Portland cement (0–6%) and bitumen emulsion (0–6%) were compacted, cured for 7, 28 and 60 days; and finally subjected to different stress sequences to study their unconfined compressive strength, indirect tensile resident modulus and indirect tensile strength tests. The durability of stabilised soil specimens was investigated by conducting wetting and drying (WD) cycling test on 7 days cured specimens. The results showed the added 4% portland cement–3% bitumen emulsion mix was ideal and produced a 179.4% reduction in the water absorption and permeability, 256.3% reduction in volume changes and 211.95% reduction in weight losses relative to a 4% cement sample. This paper presents the findings of a correlation that was conducted using non-linear regression analysis regarding the influences of the affected variables in order to establish models to predict the mixture strength parameters.     

Chemical reaction between Ag nanoparticles and TCNQ microparticles in aqueous solution

The chemical reaction between Ag nanoparticles (Ag NPs) and 7,7',8,8'- tetracycanoquinodimethane (TCNQ) microparticles (MPs) in aqueous solution for the formation of Ag-NP-decorated Ag-TCNQ nanowires is reported. Based on the results obtained by UV-vis spectroscopy and scanning electron microscopy (SEM), it is proposed that the reaction between Ag NPs and TCNQ MPs includes three stages, namely, aggregation of NPs and MPs, diffusion and reaction between NPs and MPs, and formation of Ag-TCNQ nanowires. The as-synthesized semiconducting Ag-TCNQ nanowires show good performance in nonvolatile memory devices with multiple write-read-erase-read (WRER) cycles in air.     

Manufacturing of lightweight aggregates with carbon fiber and mineral wastes

The use of carbon fiber wastes (FC) as a component to manufacture lightweight aggregates (LWAs) for concrete has been studied. Amounts of 0, 2.5, 5 and 10% (w/w) of powdered FC were added into a mineral matrix composed by 90% of granite-marble sludge (COR) plus 10% of sepiolite rejection (SEP). The mixtures were milled, kneaded with water, extruded, shaped into pellets, oven-dried and finally fired at 1100, 1125 and 1150 °C for 4, 8 and 16 min in a rotary kiln. The main technological properties of the sintered aggregates were measured. The addition of FC promoted bloating and the formation of an internal structure in which both pores and unburnt carbon fibers were present. Improvements in lightness and mechanical properties were also observed. This is the first time that carbon fibers have been embedded within aggregates, opening the way to the development of a new type of LWAs for concrete.     

Chemical oxidation of p-hydroxyphenylpyruvic acid in aqueous solution by capillary electrophoresis with an electrochemiluminescence detection system

A system of capillary electrophoresis with electrochemiluminescence detection (CE-ECL) together with UV spectroscopic and electrochemical methods were used to study the chemical oxidation of p-hydroxyphenylpyruvic acid (pHPP) by dissolved oxygen in aqueous solution. The pHPP was observed to be readily oxidized by dissolved oxygen in alkaline solution and yielded a compound that strongly enhanced the electrochemiluminescence of Ru(bpy)23+. This compound was separated and detected by a new CE-ECL system and revealed to be oxalate by being compared with an authentic sample of oxalate. The chemical oxidation mechanism of pHPP by dissolved oxygen was discussed in this paper.     

Chemical bath deposition of textured ZnO thin films in aqueous/ethanolic solution

ZnO thin films have been prepared by chemical bath deposition in aqueous/ethanolic solution. The film texture was successfully controlled by varying the volume ratio of water to ethanol. Films consisting of densely oriented nanorod arrays with the c-axis perpendicular to the substrate were fabricated in aqueous solution. The crystals became increasingly tilted as more ethanol was introduced to the solution, resulting in the cracked nanocolumns and the smoothed crystals. The crystal size was decreased with increasing ethanol content, and granular morphology was obtained in films deposited in ethanolic solution. A gradual evolution of the film texture is possibly due to the inhibited crystal growth in solution with higher ethanol content.     

Chemical reactivity of aluminium with boron carbide

The chemical reactivity of boron carbide (B₄C) with metallic aluminium (Al) was studied at temperatures ranging from 900 to 1273 K (627–1000 °C). Al–B₄C powder mixtures were cold pressed, heated for 1–450 h under 10⁵ Pa of purified argon and characterized by X-ray diffraction (XRD) optical metallography (OM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Whatever the temperature in the investigated range, B₄C has been observed to react with solid or liquid Al. As long as the temperature is lower than 933 K (660 °C), i.e. as long as Al is in the solid state, interaction proceeds very slowly, giving rise to the formation of ternary carbide (Al₃BC) and to diboride (AlB₂). At temperatures higher or equal to 933 K, Al is in the liquid state and the reaction rate increases sharply. Up to 1141 ± 4 K (868 ± 4 °C), the reaction products are Al₃BC and AlB₂: at temperatures higher than 1141 K, Al₃ BC is still formed while Al₃B₄₈C₂ (β-AlB₁₂) replaces AlB₂. In the three cases, interaction proceeds via the same mechanism including, successively, an incubation period, saturation of aluminium in B and C, nucleation and growth by dissolution–precipitation of Al₃BC and a C-poor boride and, finally, the passivation of B₄C by Al₃BC. These results are discussed in terms of solid–liquid phase equilibria in the Al–B–C ternary system, with reference to the binary invariant transformation: α-AlB₁₂ + L ⇔ AlB₂, which has been found to occur at 1165 ± 5 K (892 ± 5 °C). This revised version was published online in November 2006 with corrections to the Cover Date.     

Experimental and theoretical characterization of the engineering behavior of bitumen mixed with mineral filler

The dynamic shear rheometer (DSR) and the bending beam rheometer (BBR) were used to characterize the rheological properties of bitumen mixed with mineral filler that is smaller than 75 μm in size. The study focuses on using a rheology-based model to assess the effect of two distinctly different fillers, quartz and calcite, on the engineering behavior of the bitumen-mineral filler mastic. Four conventionally different bitumens were selected to assess the filler effect. By mathematically modeling the rheological response, predicting the rheological behavior of mastics becomes simpler and more efficient in approach. The rheological properties of bitumen-mineral filler mastics are characterized using the time–temperature superposition principle after data obtained from DSR and BBR are converted to the same unit. The stiffening effects of the filler are relatively small at short loading times or low temperatures, but are larger at higher temperatures or long loading times. This stiffening effect is found to be bitumen dependent as well as filler dependent. The validity of a micromechanical model is confirmed in this study. The Nielsen model was selected since it employs rheological parameters that could explain the filler effect. The micromechanical model shows good agreement with testing data at the filler volume fraction up to 22%.     

铝的水溶液化学特征及其聚合物生成机制

聚合氯化铝（PACl）是水处理中应用较广泛的絮凝剂。研究表明,PACl中各种铝聚合物的含量直接影响其絮凝效率。本文综述铝的水解聚合特性以及制备絮凝剂过程中的铝聚合物生成机制,着重介绍了Al13聚合物的结构特性、生成机制以及制备过程中各种因素的影响,为Al13絮凝剂的进一步研究奠定了基础。     

Expansion behaviour of glass aggregates in different testing for alkali-silica reactivity

The potential for reaction between amorphous silica in recycled glass used as aggregate in concrete and alkalis in cement is the subject of debate in current concrete literature. Whilst the ASTM C1260 accelerated mortar bar method is conventionally used for rapid ASR assessment, there is doubt about its suitability for glass aggregates. This paper reports upon a comparison of the relative ASR reactivity of various colours of recycled glass aggregates using the ASTM C1260 and C227 test methodologies. The results show that with limited exception the ASTM C1260 method does not cause glass aggregates to react by the end of the prescribed test period. In contrast, the ASTM C227 method causes all glass aggregates to react within 2 weeks, despite the test being designed for 12 months or even longer if necessary. This paper compares and contrasts the results of the two methods over a wide range of glass aggregate and cementitious systems made with two sizes of mortar bar, draws conclusions about the reasons for the differences observed and makes remarks on the expansion behaviour of glass aggregates in cementitious systems.     

Stability of the emulsion (W/O): application to the extraction of a Dawson type heteropolyanion complex in aqueous solution

Dawson type heteropolyanions form complexes with transition metals. These mixed complexes possess some remarkable electrocatalytic properties. Being soluble in aqueous and organic phases, they are used in homogeneous catalysis. In the setting of the recuperation and the regeneration of these complexes, the extraction of a mixed heteropolyanion (alpha 2P2W12Mo5O61Fe)(7-) is the subject of this work. This extraction was carried out by emulsified liquid membrane using (SPAN80) as surfactant and (TIBA) as extractant. Sulfuric acid was used as the internal phase. The stability of the emulsion was studied according to different parameters and the extracting efficiency in optimal conditions was found to be 70%.     

应用膜技术精制水溶性染料

采用CA卷式纳滤膜进行了NT染料水溶液脱盐和浓缩的过程研究 .在 1.8MPa压力下经膜过程处理后 ,NT染料水溶液中的NaCl浓度从 1.0 5mol/L降到 0 .0 4 9mol/L以下 ,NT浓度浓缩到 0 .2 5mol/L以上 ,NT成份的平均截留率达 99 8% .在经较长时间连续运转后 ,膜元件仍然具有良好的抗污染能力 ,但是当NT组份浓缩到 0 .3mol/L左右时 ,可能会在膜表面形成凝胶层 ,使得渗透流率异常下降 ,NaCl的截留率上升 .工艺生产表明 ,该卷式纳滤膜用于NT染料的脱盐浓缩是可行的     

Reactivity of valganciclovir in aqueous solution

The rates of hydrolysis of valganciclovir to ganciclovir and L-valine and isomerization of the R and S diastereomers of valganciclovir in aqueous buffer solution from pH 3.8 to 11.5 were determined at 37 degrees C. The kinetics of hydrolysis were first order for at least two half-lives in neutral and basic solutions. In acidic solutions where less than 10% degradation occurred, the rate of hydrolysis was determined assuming a first-order loss in drug. At 37 degrees C and pH 7.08, the half life is 11 h. The maximum stability at the pH values studied occurred at pH 3.81 with a half life of 220 days. The kinetics of the approach to equilibrium for the isomerization were first order and the ratio of the R:S isomer at equilibrium was 52:48. Isomerization was approximately 10 fold faster than hydrolysis over the pH range studied with a half-life at pH 7.01 of 1 h. The maximum stability toward isomerization (t1/2>533 h) occurs at a pH below 3.8. The pH-rate profile for the hydrolysis and the isomerization reaction are best described by hydroxide ion catalyzed mechanisms. In acidic and neutral solutions, the hydroxide reacts with the protonated form of the drug, while in basic solutions, the hydroxide reacts with the neutral form of the drug.     

Degradation of tobramycin in aqueous solution

The kinetics of degradation of tobramycin (Ne-De-Ka) in aqueous solution was studied as a function of pH. Tobramycin hydrolyzes in acidic solution to yield kanosamine (Ka-OH) and nebramine (Ne-De-OH) with a pseudo first-order rate constant of 2.7 × 10^-6 s^-1 in 1 N HCl at 80°C. The activation energy for the acid catalyzed hydrolysis is 32 kcal mol^-1. In basic solution, the hydrolysis products are deoxystreptamine (De-OH), nebramine (Ne-De-OH) and deoxystreptamine-kanosaminide (HO-De-Ka). The pseudo first-order rate constant for the hydrolysis in 1 N KOH is 1 × 10^-8 s^-1 at 80°C. The activation energy for the base catalyzed hydrolysis is 15 kcal mol^-1. Tobramycin is very stable towards hydrolysis at neutral pH; however, it rapidly oxidizes giving several products including De-OH, Ne-De-OH, and HO-De-Ka. In pH 7 phosphate buffer (0.01 M), the t₉₀ value is 70 hr at 80°C.     

Degradation of tobramycin in aqueous solution

Abstract

The kinetics of degradation of tobramycin (Ne-De-Ka) in aqueous solution was studied as a function of pH. Tobramycin hydrolyzes in acidic solution to yield kanosamine (Ka-OH) and nebramine (Ne-De-OH) with a pseudo first-order rate constant of 2.7 × 10^?6 s^?1 in 1 N HCl at 80°C. The activation energy for the acid catalyzed hydrolysis is 32 kcal mol^?1. In basic solution, the hydrolysis products are deoxystreptamine (De-OH), nebramine (Ne-De-OH) and deoxystreptamine-kanosaminide (HO-De-Ka). The pseudo first-order rate constant for the hydrolysis in 1 N KOH is 1 × 10^?8 s^?1 at 80°C. The activation energy for the base catalyzed hydrolysis is 15 kcal mol^?1. Tobramycin is very stable towards hydrolysis at neutral pH; however, it rapidly oxidizes giving several products including De-OH, Ne-De-OH, and HO-De-Ka. In pH 7 phosphate buffer (0.01 M), the t₉₀ value is 70 hr at 80°C.     

Removal of cadmium, zinc, manganese and chromium cations from aqueous solution by a clay mineral

Vermiculite, a 2:1 clay mineral, was applied as adsorbent for removal of cadmium, zinc, manganese, and chromium from aqueous solutions. Parameters such as time of reaction, effect of pH and cation concentration were investigated. All isotherms were L type of the Gilles classification, except zinc (type S). The adsorbent showed good sorption potential for these cations. The experimental data was analyzed by Langmuir isotherm model showing reasonable adjustment. The quantity of adsorbed cations was 0.50, 0.52, 0.60, and 0.48 mmol g(-1) of Cd(2+), Mn(2+), Zn(2+), and Cr(3+), respectively.     

Effective viscosity of an emulsion in a surfactant solution

A surfactant affects the effective viscosity of an emulsion because of capillary phenomena in shear flow. The surfactant gives the emulsion non-Newtonian behavior.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 5, pp. 752—759, May, 1988.