Electrophoretic Deposition Behavior of Aqueous Nanosized Zinc Oxide Suspensions

The rheological behavior and electrophoretic deposition (EPD) of ZnO nanopowder (nano-ZnO) in aqueous media have been described. A cationic polyelectrolyte (polyethylenimine, PEI) was used to disperse and modify the surfaces of the ZnO nanoparticles. The rheological properties of the ZnO aqueous suspension were investigated by measuring the viscosity versus the pH and amount of dispersant. The EPD processing was conducted via cathodic electrodeposition, using stable suspensions with low viscosity, and the depositional behavior was investigated. Bubble-free nano-ZnO deposits with uniform microstructures were successfully obtained, which was an indication of good sintering behavior.     

Sorption of Cobalt on Activated Carbons from Aqueous Solutions

Abstract

The efficiencies of 15 commercially available activated carbons were tested for the separation of trace cobalt (⁶⁰Co) in buffer solutions at pH 5.0, 6.7, and 9.1. On the basis of the results four carbon products, Diahope-006, Eurocarb TN5, Hydraffin DG47, and Norit ROW Supra, were selected for further study. These carbons represented varying (low, medium and high) cobalt removal efficiencies and were prepared of three typical raw materials: peat, coconut shell or coal. Study was made of the effects on sorption efficiencies of factors of interest in metal/radionuclide-bearing waste effluents. These factors were pH, sodium ions, borate, and citrate.     

Copper Sorption from Aqueous Solutions by Plasma Modified Polyacrylonitrile Beads

Summary The adsorption of Cu(II) ions from aqueous solutions on acrylonitrile(AN) copolymer sorbents has been studied. Porous sorbents from acrylonitrile copolymer-90.6% acrylonitrile (AN), 8.1% methylmethacrylate (MMA) and 1.4% 2-acrylamido-methylpropensylfonic acid (AMPSA) have been prepared and modified by ammonia, air and ethylenediamine plasma. Fourteen types of sorbents have been obtained changing plasma agent and plasma vacuum. The Cu(II) ions uptake has been studied and the sorbent with best sorption characteristics determined. The best sorption uptake has been achieved for the modified sorbent obtained at ethylenediamine plasma modification under 5 Pa plasma vacuum (PAN1-1.20 mgeq/g). Effect of sorbents regeneration after different elution cycles has also been investigated . The sorbents showed high effectiveness of regeneration towards Cu(II) ions, which was above 50% after the IV cycle of elution.     

Column Sorption of Citric Acid from Aqueous Solutions Using Tri-n-octylamine-Impregnated Macroporous Resins

Abstract

Column sorption of citric acid from aqueous solutions using tri-n-octylamine (TOA)-impregnated macroporous resins was studied at 298 K. The breakthrough curves were measured as a function of the feed flow rate, citric acid concentration in the feed solution, TOA concentration in the resin phase, and type of resin. It was found that the type of resin played a most important role in determining the saturated capacity under comparable conditions. The desorption of citric acid from loaded resins was also evaluated with various eluants, including HCl, HNO³, H²SO⁴, and Na²CO³     

Evaporation of Zinc Oxide from Spinel Solid Solutions in Vacuum

The mechanism for the evaporation of ZnO from powders of (Zn₀₂Co_0.8)O·Al₂O₃ (ZCA) and (Zn_0.2Ni_0.8)O·Al₂O₃ (ZNA) spinels was studied at 1335° to 1500°C in vacuum of 3×10⁻⁵ to 10⁻⁴ torr. The evaporation of ZnO occurred in two stages: at a constant rate in the first and a decreasing rate in the second. The rate-determining process was analyzed as a decomposition reaction at the first stage and as the conjugated process of decomposition reaction and diffusion in the solid at the second. The evaporation rate constant and surface emissivity showed a similar dependence on temperature. The ratio of the concentration of ZnO at the surface to the initial concentration was =0.7 when the first stage of evaporation changed to the second.     

二氧化钛和氧化锌的光催化活性(英)

通过二氧化钛和氧化锌的光催化作用研究,讨论了有机及无机表面处理对该作用的影响。与无机处理相比,有机表面处理对降低二氧化钛和氧化锌的光催化活性有很大影响,进而显著地减小了其在化妆品中的副作用,具有重要的意义。     

Sorption Behavior of Carrier-Free Technetium-99m on Zinc Dust

Abstract

The sorption behavior of ^99mTc on zinc dust was studied as a function of pH. Optimum conditions have been found for the preconcentration of traces of Tc by zinc. The influence of surface-active substances and of complexing agents on the sorption of trace amounts of Tc on zinc dust has been also studied.     

磺化木质素水溶液的流变行为

采用旋转黏度仪研究三种磺化木质素(钙离子、镁离子和钠离子)的水溶液流变行为,发现磺化木质素(LGS)水溶液的流变行为随着剪切速率的变化显示出不同的特征,其中存在一个临界剪切速率(γc),将剪切速率分为低和高两个区域。γc与相对分子质量和温度(t)都有关,其γc―t呈现非常好的线性关系,从而可以外推得到一个特性剪切速率[γ]。而由于[γ]不仅是一个唯一值,而且正比于特性黏度[η],所以可能是一个新的高分子流变性能的参数,可以用来预测高分子的流变性能,或根据高分子的相对分子质量预测其流变行为。通过研究LGS水溶液的浓度对流变性能的影响发现,低浓度时具有切力变稀和增稠两种不同的流变行为,而高浓度时仅有单一的切力变稀或增稠行为。     

Absorption of Nitrous Oxide from Air by Aqueous and Organic Solutions

Theoretical Foundations of Chemical Engineering - Findings from a study of the N2O absorption from an air flow in various aqueous and organic solutions at 293–298 K were reported. The maximum...     

Sorption and Reduction of Hexavalent Chromium from Aqueous Solutions by Surface Modified Biochars

The surface of wheat straw-based biochar was modified by a pretreatment using H₃PO₄. Biochars with different surface characteristics were obtained and characterized. Their reducing and sorption capacities for aqueous Cr(VI) were evaluated. The removal of Cr(VI) were enhanced with an increase in biochar surface acidity. The sorption performance was related to the equilibrium concentration. Oxygen-containing groups were involved in Cr(III) complexation, some of which were formed due to Cr(VI) oxidation. The competitive sorption of proton was evident for over protonated biochars at low range. Biochar porosity also played a role. The influences of other factors were also discussed.     

Liquid-Liquid Extraction of Zinc with Aliquat 336-S-Br from Aqueous Bromide Solutions

Abstract

A new solvent extraction system has been developed for zinc in aqueous bromide solution using Aliquat 336-S-Br-xylene solution as an extractant. A 1 mg/ml zinc solution is extracted essentially quantitatively with an equal volume of 5% Aliquat 336-S-Br-xylene solution in 15 sec. The extracted zinc can be stripped from the nonaqueous layer with a series of aqueous solutions including Na₂SO₃ (≥m 1.0 M) NaOH (≥m 0.5 M), NH₃ (≥m 0.5 M), ethylenediamine (≥m 0.3%), and EDTA (≥m0.5%). The extraction is quantitative only from acidic solutions. High aqueous to organic phase ratios can be utilized without loss of extraction efficiency.     

Adsorption of Microamounts of Silver on Manganese Dioxide from Acid Solutions

Abstract

Adsorption of microamounts of silver on manganese dioxide from nitric and perchloric acid solutions has been studied and optimized with respect to shaking time, concentrations of electrolyte, adsorbent, and adsorbate. Maximum adsorp- tion (>99.5%) has been achieved from 0.01 mol/dm³ acid solution using 50 mg oxide at 10^?5 mol/dm³ silver concentration after 30 min shaking. The adsorption decreases with increasing concentration of acid and adsorbate from both the acids. The presence of a 10⁴-fold greater concentration of cyanide, thiocyanate, thiosulfate, and Pb(II) than silver reduces the adsorption drastically. The adsorption of silver follows the Freundlich adsorption isotherm over the entire concentration range investigated from 9.27 × 10^?6 to 2.92 × 10^?3 mol/dm³ with a value of A = 49 mmol/g and 1/n = 0.93. Moreover, the Langmuir adsorption isotherm is also valid except at the lowest and highest concentrations. The values of the limiting adsorption concentrtion (C_m ) have been found to be 1 mmol/g and of the equilibrium constant for adsorption 87 dm³/mol at 23 ± 2°C.     

Aqueous Precipitation of Spherical Zinc Oxide Powders for Varistor Applications

Aqueous precipitation has been used to prepare spherical ZnO particles. These powders have been shown to be suitable for use in the preparation of varistors. The uniform size distribution and uniform coating of these powders with the appropriate dopants allowed fabrication of varistors with improved properties over those fabricated from conventionally ball-milled and calcined powders. The improved properties were a high coefficient of nonlinearity (∼44) in the nonohmic region, a sharp change in electrical behavior from ohmic to nonohmic, and a high resistivity (5×10¹² SOM°m) at low voltages.     

Sorption of Citric Acid from Aqueous Solutions by Macroporous Resins Containing a Tertiary Amine Equilibria

Abstract

Experiments were conducted on equilibrium distribution of citric acid between relatively concentrated aqueous solutions and macroporous resins containing tri-n-octylamine (TOA). The equilibrium data were well described by the Langmuir isotherm equation. Chemical model analysis of the results showed that the sorption could be also explained by the formation of an acid-amine complex with general composition (acid)(TOA)_q in the resin phase. The loss of amine from the impregnated resins and the effect of temperature on equilibrium distribution were also discussed.     

Effect of Ring-Size Variation within Dibenzocrown Ether Resins upon Ion-Pair Sorption of Alkali-Metal Cations from Aqueous and Aqueous Methanol Solutions

Abstract

A batch analysis method has been developed for evaluation of metal salt sorption by crown ether polymers. Selectivity in competitive alkali-metal chloride sorption by a series of formaldehyde condensation polymers of dibenzocrown ethers is influenced by the relationship between the crown ether cavity size and metal ion diameter, as well as the degree of hydration of the metal salt. Effective and selective sorption of KCl from the other alkali-metal chlorides was obtained with a dibenzo-18-crown-6 resin. Excellent sorption selectivity for the monovalent metal chlorides was noted for competitive ion-pair sorption of NaCl, KCl, MgCl₂, and CaCl₂ by this resin. This resin was examined as a stationary phase for selective column separation of KCl from alkali-metal chlorides and of KCl and NaCl from alkali-metal and alkaline-earth chloride mixtures in 80% methanol—20% water.     

Synthesis of Gallium Oxide Hydroxide Crystals in Aqueous Solutions with or without Urea and Their Calcination Behavior

Gallium oxide hydroxide (GaOOH· x H₂O) single crystals were synthesized in aqueous solutions by using two different precipitation techniques: homogeneous decomposition of urea and forced hydrolysis in pure water. Precipitation of crystals started at exactly the same pH value (i.e., 2.05 at 85°C) in both cases. The morphology of crystals turned out to be quite different (zeppelin-like with urea, rodlike without urea) in each of the above methods. Calcination of these gallium oxide hydroxide crystals in air at temperatures ≥500°C transformed them into Ga₂O₃. Characterization of the samples was performed by X-ray diffractometry, scanning electron microscopy, thermogravimetry/differential thermal analysis, Fourier transform infrared spectroscopy, and ICP, carbon, and nitrogen analyses.     

The Effect of Rate of Flow on the Sorption of Dye by a Nylon Fabric from Aqueous Solutions

The rate of sorption of an acid dye by a nylon fabric is strongly influenced by mass–transfer processes in the liquid phase, even at rates of flow far exceeding those to be expected in existing commercial dyeing equipment. It is suggested that concentration gradients exist in the solution within the yam elements of the fabric, and the individual fibres in the yarn elements are shown to differ in their accessibilities to dye; the yarn cross–sections are ‘ring–dyed’. In spite of these complexities the major features of the overall mass–transfer process are well represented by a simple model based on the concept of an equivalent diffusional boundary resistance to mass transfer. The numerical values obtained for δ are comparable with the yarn dimensions, which reflects the ‘coalescence’ of the individual boundary layers to form a region within the yarn elements in which dye transport by convective diffusion in the liquid phase limits the overall mass–transfer rates.     

锌灰制备活性氧化锌工艺的研究

以冶炼厂废锌灰为原料,经硫酸浸取,考察了不同工艺条件对锌的浸出率的影响。实验结果表明:锌灰在50℃下浸取,pH值为1.5时,可使锌灰中锌的溶出率达93.5%。碱式碳酸锌最佳水解温度为40℃,水解时间为2 h,pH值为7.5时,溶液中锌含量为12 g/L,得到96%以上的水解率。     

锌精矿湿法制氧化锌的研究

用工业硫酸浸取焙烧脱硫后的锌精矿,经过一系列的除杂步骤,湿法制取氧化锌,所得产品氧化锌的纯度达99.71％,各项技术指标均符合产品标准,其中元素锌的总回收率达到87％以上。     

Biosorption of Zinc from Aqueous Solutions by Rice Bran: Kinetics and Equilibrium Studies

Abstract

Rice bran, an agricultural by‐product, was used for the removal of zinc ions from aqueous solution. The work considered the determination of zinc‐biomass equilibrium data in batch system. These studies were carried out in order to determine some operational parameters of zinc sorption such as the time required for the Zinc‐biosorbent equilibrium, the effects of biomass particle size, pH, and temperature. The results showed that pH has an importance effect on zinc biosorption capacity. The biosorbent size also affects the zinc biosorption capacity. The sorption process follows pseudo‐second‐order kinetics. The intraparticle diffusion may be the rate‐controlling step involved in the adsorption zinc ions onto the rice bran up to 30 min. The equilibrium data could be best fitted by the Langmuir sorption isotherm equation over the entire concentration range (40–160 mg/dm³). Thermodynamic parameters, such as ΔG°, ΔH°, ΔS°, have been calculated. The thermodynamics of zinc ion/rice bran system indicate spontaneous and endothermic nature of the process.