One-step green synthesis of cuprous oxide crystals with truncated octahedra shapes via a high pressure flux approach

Cuprous oxide (Cu₂O) was synthesized via reactions between cupric oxide (CuO) and copper metal (Cu) at a low temperature of 300 °C. This progress is green, environmentally friendly and energy efficient. Cu₂O crystals with truncated octahedra morphology were grown under high pressure using sodium hydroxide (NaOH) and potassium hydroxide (KOH) with a molar ratio of 1:1 as a flux. The growth mechanism of Cu₂O polyhedral microcrystals are proposed and discussed.     

Chemical modification of cellulose extracted from sugarcane bagasse: Preparation of hydroxyethyl cellulose

Cellulose was extracted from sugarcane bagasse by alkaline extraction with sodium hydroxide followed by delignification/bleaching using sodium chlorite/hexamethylenetetramine system. Factors affecting extraction process, including sodium hydroxide concentration, hexamethylenetetramine concentration and temperature were studied and optimum conditions for alkaline extraction were found to be boiling finely ground bagasse under reflux in 1 N sodium hydroxide solution and then carrying out the delignification/bleaching treatment at 95 °C using 5 g/l sodium chlorite together with 0.02 g/l hexamethylenetetramine. The extracted cellulose was used in the preparation of hydroxyethyl cellulose through reaction with ethylene oxide in alkaline medium. Factors affecting the hydroxyethylation reaction, like sodium hydroxide concentration during the alkali formation step, ethylene oxide concentration, reaction temperature and reaction duration were studied. Optimum conditions for hydroxyethylation reaction were using 20% NaOH solution and 200% ethylene oxide (based on weight of cellulose), carrying out the reaction at 100 °C for 60 min.     

氢氧化钠沉淀分离铜、钯的动力学研究及分析应用

进行了氢氧化钠沉淀分离铜钯的动力学研究,计算了用该法分离铜钯对测定引起的误差,将该法用于测定乙醛催化剂中的钯含量,获得满意结果。     

The activity of NaOH buffered by silicate solids in molten sodium acetate-water at 317°C

Silica and sodium acetate are present in the steam generator tube sheet crevices of many nuclear power plants. Trace solutes in the condensate are tremendously concentrated in the crevices by boiling. Sparingly soluble sodium silicates and other solids precipitate from the crevice liquid leaving an extremely concentrated molten mixture of water, sodium acetate and other salts. The precipitates buffer the activity of sodium hydroxide in the superheated liquid that remains. The activity of NaOH corresponding to the buffers quartz/sodium disilicate and sodium disilicate/sodium metasilicate at 317°C has been determined experimentally. The sodium hydroxide content of a sodium acetate-water melt buffered by these reactions was determined bychemical analysis, and the corresponding activity of NaOH at temperature was calculated using the recently published Pitzer-Simonson Model of molten salt-water mixtures. The molten mixture of sodium acetate and water plays the role of solvent in these experiments and calculations. The free energies of formation of solid sodium silicates at 317°C were also determined. The activity of NaOH corresponding to other silicate and phosphate buffers was calculated using published thermodynamic data and estimated from phase diagrams.     

Electrochemical and surface analytical study of the formation of oxide films on monel-400 and copper in alkaline media

The nature of the oxide films formed on monel-400 and copper in presence of NaOH and N-methylpyrrolidine (a volatile amine) at pH 9.5 and in 0.1 M KNO₃ medium were investigated. The oxide films were grown by applying an anodic potential of +0.4 V (vs saturated calomel electrode) for 30 min. The compositions of the surface oxide films were analysed by X-ray photoelectron spectroscopy. In the case of copper in NaOH medium, Cu(0) and a very small amount of copper hydroxide were observed. However, in amine medium, Cu(0) and Cu-amine complex were found. For monel in NaOH, the anodic film was found to contain hydroxides of both copper and nickel. After sputtering, this film showed a small amount of metal oxide below the hydroxide layer as confirmed by the oxygen peak. In amine medium the anodic film was found to contain only nickel hydroxide and metallic copper. The depth profile analysis of films showed that the film developed was very thin and the nickel hydroxide was sputtered very easily from the film. Received: 27 May 1997 / Accepted: 8 September 1997     

Differential-pulse anodic-stripping voltammetric determination of traces of lead in high-purity copper after its separation by ion exchange

Trace amounts of lead in copper can be determined by differential-pulse anodic-stripping voltammetry after separating it from the matrix. Lead was quantitatively retained on a small Dowex 1-X4 ion-exchange column, without retaining copper when present as a copper-amine complex in solutions containing 0.2 M sodium hydroxide. Subsequent desorption was done with 2 M nitric acid. After deposition for 1 min on a hanging mercury drop electrode and subsequent stripping, the limit of detection was 2 ng ml^?1 and the limit of quantification was 6.6 ng ml^?1. Recoveries of lead were checked by standard addition to copper solution.     

Synthesis and properties of a new chelating resin containing the oxime group

A macroreticular polystyrene-based chelating resin with oxime and diethylamino functional groups has been synthesized. The resin is stable in acid and alkaline solutions; no decrease in nitrogen content or capacity for sorption of copper(II) is observed when it is exposed to 3M hydrochloric acid and 1M sodium hydroxide for 7 days. The resin has higher selectivity for copper(II) than for other metal ions tested and the time required for 50% uptake of copper(II) is 15 min. The highest capacity for copper(II) is 2.0 mmole/g at pH 6.0. In a column operation, quantitative recovery of copper(II) is achieved by elution with 1M hydrochloric acid, and the resin can be used repeatedly.     

Extraction of soluble fiber from distillers' grains

The feasibility of using coproducts from dry grind corn ethanol production as a substrate for the production of soluble fiber was examined. Acid- and base-catalyzed hydrolysis experiments were performed using sulfuric acid and sodium hydroxide to partially hydrolyze hemicellulose content of whole stillage, a precursor to distillers' grains, to soluble fiber. The influences of temperature, reaction time, and hydrolyzing agent concentration on the formation of soluble fiber were studied. Soluble fiber was recovered by precipitation in a 95% ethanol solution. Results indicate that appreciable quantities of soluble fiber may be extracted using either acid- or base-catalyzed reactions. The highest yield of soluble fibers was 13.2 g per 100 g-db of treated whole stillage using one weight percent sodium hydroxide at 80oC for 1 h. HPLC analysis was used to quantify the amount of monomeric sugars which were formed during the hydrolysis procedures.     

Spectrophotometric determination of copper in alkaline solutions and evaluation of some hydroxy-substituted 1,10-phenanthrolines as chromogenic reagents

Seven new hydroxy-substituted 1,10-phenanthroline derivatives have been evaluated as chromogenic reagents for the determination of copper in strongly alkaline solution. The most sensitive of these, 2,9-dimethyl-4,7-dihydroxy-1,10-phenanthroline, has proven to be highly effective in a simple, rapid procedure for determining trace amounts of copper in sodium hydroxide, potassium carbonate, sodium phosphate or ammonium hydroxide.     

Facile synthesis and characterization of β-cobalt hydroxide/hydrohausmannite/ramsdellitee/spertiniite and tenorite/cobalt manganese oxide/manganese oxide as novel nanocomposites for efficient photocatalytic degradation of methylene blue dye

In this paper, our research team has synthesized new nanocomposites by simple precipitation/ignition method and using low-cost chemicals. Hence, β-cobalt hydroxide/hydrohausmannite/ramsdellitee/spertiniite and tenorite/cobalt manganese oxide/manganese oxide new nanocomposites were synthesized by precipitation of Mn(II)/Co(II)/Cu(II) solution using sodium hydroxide and ignition of precipitate at 700 °C for 3 hrs, respectively. The synthesized nanocomposites were characterized using different instruments such as energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), nitrogen gas sorption analyzer, and UV–vis spectrophotometer. Energy dispersive X-ray analysis revealed that the nanocomposite formed as a result of precipitation consists of copper, cobalt, manganese, and oxygen where the weight percentages are equal to 31.73, 27.01, 17.26, and 24 %, respectively. Also, the nanocomposite formed as a result of ignition consists of copper, cobalt, manganese, and oxygen where the weight percentages are equal to 31.26, 23.87, 14.56, and 30.31 %, respectively. Transmission electron microscope revealed that the nanocomposites formed as a result of precipitation and ignition consist of polyhedral and spherical shapes with an average diameter of 34.50 and 28.56 nm, respectively. The synthesized nanocomposites were used as new photocatalysts for the efficient degradation of methylene blue dye. 0.05 g of the synthesized nanocomposites degrade 100 % of 50 mL of 15 mg/L of methylene blue dye solution within 25 min in the presence of H₂O₂ under UV light.     

Temperature driven morphological changes of hydrothermally prepared copper oxide nanoparticles

The size and shape of nanocrystals have a strong effect on the optical, electrical and catalytic properties. Therefore, controlling the size, shape and structure of nanocrystals is technically important. The controlled synthesis of CuO nanostructures was achieved using a hydrothermal process by simply controlling the precipitation reaction temperature between copper nitrate trihydrate and sodium hydroxide. The Scanning Electron Microscopy (SEM), EDS, XRD, and FTIR analysis revealed that the synthesized product at 200 °C is of pure copper oxide particles. From Scherrer formula, the prepared CuO particles varied approximately 3–7 nm in size simply by varying the reaction temperature. The synthesized particles exhibited a regular flake like morphology and had a uniform size distribution. The morphology and size depend on the reaction conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

Needle-type colloidal copper (II)hydroxide particles

Stable dispersions of fine (< 0.05m) needle-type copper(II) hydroxide particles were prepared at room temperature by admixing sodium acetate and ammonia to copper sulfate solution. The particle length and width could be altered with the concentration of reactants. The rate of dissolution of copper(II) hydroxide particles in doubly distilled water at room temperature is time dependent, which is due in part to the formation of a mononuclear complex solute (CuOH⁺). After extended times (e.g., 18 h), the particles underwent phase transformation, resulting in longer needles of higher degree of crystallinity.Supported by the Griffin Corp., Valdosta, Georgia.     

Determination of bismuth, selenium and tellurium in nickel-based alloys and pure copper by flow-injection hydride generation atomic absorption spectrometry—with ascorbic acid prereduction and cupferron chelation-extraction

Diverse matrix effects on the determination of bismuth, selenium and tellurium (μg g⁻¹) in nickel-based alloys and pure copper by flow-injection hydride generation atomic absorption spectrometry (FIAS-HGAAS) were investigated. Sodium tetrahydroborate was used as the reductant. The separation of analytes from copper matrix was mandatory while the analytes were successfully determined without being separated from the alloy matrix. Hydrochloric acid was effective in the prereduction of bismuth and selenium, however, it did not give any satisfactory result for tellurium in nickel-based alloys. In this work, 5% (w/v) ascorbic acid was proved effective for the prereduction of tellurium.Successful determination of tellurium in copper was achieved when N-nitroso-N-phenylhydroxylamine (cupferron) chelation-extraction was employed for the separation of tellurium from copper matrix. Cupferron chelation-extraction was performed in phosphate buffer (a mixture of 0.2 mol l⁻¹ sodium phosphate and 0.1 mol l⁻¹ citric acid). Lanthanum hydroxide coprecipitation at pH 10.0±0.5 was effective for bismuth and selenium. Standard reference materials of nickel-based alloys and pure copper were analyzed using the proposed methods. The linear range for the calibration curves were 0.30-15 and 0.20-10 ng ml⁻¹ for BiH₃ and H₂Se, respectively, with a correlation coefficient of 0.9995. For H₂Te, the linear range for the calibration curves was 0.50-12 ng ml⁻¹ with the correlation coefficient of 0.9994. Good agreement was obtained between experimental values and certified values. Satisfactory recovery ranged from 91±1 to 106±2% was obtained from five replicate determinations.     

Extraction and spectrophotometric determination of copper(II) with 1,1,1-trifluoro-3-(2-thenoyl)acetone

Copper(II)-trifluorothenoylacetone complex in chloroform does not undergo decomposition when scrubbed with sodium hydroxide solution. This allows the complete removal of the residual reagent, and a highly sensitive method for the extraction and spectrophotometric determination of copper(II) results.     

Simulation and modeling of synthesis Cu nanoparticles in sodium alginate media by means of expert systems

This research was to apply the combination of the particle swarm optimization method and artificial neural network training with the aim of building a quantitative model to forecast the size of copper nanoparticles (Cu-NPs) prepared in sodium alginate. Sodium alginate, sodium hydroxide, copper sulfate, hydrazinium hydroxide, and ascorbic acid were used as stabilizer, pH moderator, copper precursor, reducing agent, and antioxidant, respectively. The results showed that the different sizes of Cu-NPs were obtained by changing these functions. Meaning that by increasing the amount of sodium alginate and or increase the volume of hydrazine hydrate, particle sizes of Cu-NPs were reduced. Other variables had the opposite effects due to the increase of the size of the Cu-NPs. The prediction results were remarkably in agreement with the experimental data with a correlation coefficient of 0.99 and a mean square error of 0.0058.     

Sequential extraction for the speciation of some heavy metals in soils

The five step sequential extraction for speciation of copper and nickel originally designed for sediments has been applied to soil samples. The extractant solutions were: 1 mol/l ammonium acetate, 1 mol/l hydroxylammonium chloride in 25% acetic acid (1∶1), 0.1 mol/l hydrochlorid acid, 0.5 mol/l sodium hydroxide and 8 mol/l nitric acid. The residue was decomposed by HF and HNO₃. Using this procedure the metal fraction bound to the organic matter can be distinguished. The concentrations of analytes were determined in the soil extracts by FAAS and ETAAS. Accuracy was assessed by comparing the sum of the contents of copper and nickel in soil extracts with the total certified values of CRMs of soils. The overall recovery values for nickel was 84–105% and for copper 105–114%.     

Spectrophotometric Determination of Acyclovir and Amantadine Hydrochloride through Metals Complexation1

A simple spectrophotometric method for determination of some antiviral drugs, such as acyclovir and amantadine hydrochloride in pure and dosage forms, have been developed. The proposed method is based on the reactions of the selected drugs and metals. Acyclovir was reacted with copper (II) and cobalt (II) using a borax/sodium pH 9 hydroxide buffer, and in a non-aqueous medium using 1% pyridine in methanol, respectively.The formed complexes were absorbed maximally at A, 290 nm and at X 287 nm. The method determined from 112–1620 g/mL of acyclovir, with a mean percentage of recovery of 99.32 ± 0.63 and of 98.77 ± 0.70 for copper (II) and cobalt (III), respectively.The suggested method was applied to a Novirus capsule, and its validity was ascertained by the standard addition technique. In addition, amantadine hydrochloride was allowed to react with iron (III) at pH 3 adjusted with 0.1 M ammonium hydroxide. The formed complex absorbed maximally at 295 nm. This method determined from 94–940 g/mL of amantadine hydrochloride with a mean percentage of recovery of 99.49 ± 0.57. The suggested method was applied to an Adamine capsule, and its validity was ascertained by the standard addition technique.     

2,7-TADN极谱特性研究(Ⅱ)-铜(Ⅱ)-2,7-TADN-乙二胺配合物吸附波测定痕量铜

研究了Cu²⁺-2,7-TADN-乙二胺配合物的极谱行为。在氢氧化钠、乙二胺(en)和2,7-TADN底液(pH约为12)中,铜(Ⅱ)能产生Cu²⁺-2,7-TADN-en三元配合物吸附波,其峰电位为-0.86V。铜含量在2.0×10^-8-5.0×10^-6M范围内,峰高与铜浓度成线性关系。检测下限达1.0×10^-8M。     

Single step modification of copper electrode for the highly sensitive and selective non-enzymatic determination of glucose

A non-enzymatic sensor was developed for the determination of glucose in alkaline medium by anodisation of copper in sodium potassium tartrate solution. The morphology of the modified copper electrode was studied by scanning electron microscopy, and its electrochemical behavior by cyclic voltammetry and electrochemical impedance spectroscopy. The electrode enables direct electrocatalytic oxidation of glucose on a CuO/Cu electrode at 0.7 V in 0.1 M sodium hydroxide. At this potential, the sensor is highly selective to glucose even in the presence of ascorbic acid, uric acid, or dopamine which are common interfering species. The sensor displays a sensitivity of 761.9 μA mM^?1 cm^?2, a linear detection range from 2 μM to 20 mM, a response time of <1 s, and a detection limit of 1 μM (S/N = 3). It was tested for determination of glucose level in blood serum.     

Investigation on drying conditions and assays of amidosulfuric acid and sodium carbonate by acidimetric coulometric titration and gravimetric titration

Amidosulfuric acid and sodium carbonate as standards for acid–base titrimetry were assayed by coulometric titration and gravimetric titration. Amidosulfuric acid was directly assayed by coulometric titration with electrogenerated hydroxide ions, and sodium carbonate was assayed by gravimetric back-titration. For sodium carbonate, excess amount of sulfuric acid, whose concentration was determined by coulometric titration, was added to sodium carbonate, and then gravimetrically back-titrated using a sodium hydroxide solution whose concentration was determined by gravimetric titration using the sulfuric acid. The accuracy of the coulometric titration for amidosulfuric acid and sulfuric acid was evaluated by examining the current efficiency of pulse electrolysis, the amount of the electrolysis current used, and the time spent for a titration. In addition, the drying conditions for high purity primary standards have a significant effect on the titration results due to changes in the acid–base assay. The suitable drying conditions for amidosulfuric acid and sodium carbonate were evaluated by mass-change measurements, coulometric titration and gravimetric titration. The measurement uncertainties were estimated from the uncertainties on the titration processes. Finally, the assays of amidosulfuric acid and sodium carbonate were 99.986% ± 0.010% (k = 2) after drying at 50 °C for 2 h, and 99.970% ± 0.016% (k = 2) after drying at 280 °C for 4 h, respectively. In addition, the international consistency was confirmed by measuring certified reference materials (CRMs) available from different National Metrology Institutes, and the compatibility of values among CRMs was experimentally ascertained.