Sorption-catalytic method for the determination of copper (II) in combination with planar chromatography

An activating action of hexamethylenediamine is revealed in the copper (II)-catalyzed indicator reaction of iron (III) reduced by sodium thiosulfate. It is shown that the addition of hexamethylenediamine to a mobile phase (thin-layer chromatography) and the impregnation of paper with hexamethylenediamine (paper chromatography) enhance the efficiency of metal separation for the model mixture containing Cu (II), Hg (II), Cd (II), and Pb (II). The techniques for the sorption-catalytic determination of copper (II) with the help of Sorbfil plates, including those in combination with thin-layer chromatography, are developed; they work within the concentration range from 0.005 to 10 ??g/mL, the detection limit being 4 ng/mL, which is approximately an order of magnitude lower than in solution. The methods are tested in analysis of waste and river waters.     

Some aspects of reactivity of copper(I) sulphide with copper(II) sulphate

The reaction of Cu₂S with CuSO₄ in SO₂ at T>710 K proceeds forming liquid intermediates, Cu₂SO₂ and Cu₂SO₄, which decompose to solid products. Only SO₂ is a gaseous product out of all the intermediate reactions. The rate of each step is dependent, in a complex way, upon the liquid content of the reacting mixture. The relations of major importance between the rates of individual intermediate reactions, the liquid content of the reacting mixture, the composition of the liquid and the initial composition of the substrates mixtures have been discussed.     

Phase transitions in copper(II) orthovanadate

Data on the polymorphs of copper(II) orthovanadate are reported. The Cu₃V₂O₈ phase synthesized in this laboratory exhibits phase transitions between 460° and 560°C. These phase transitions are identified through detailed DTA and high temperature XRD techniques; it is observed that these structural transitions are rapid and reversible. The crystal structure of Cu₃V₂O₈ is similar to that of Mg₃V₂O₈, Zn₃V₂O₈, Co₃V₂O₈ and Ni₃V₂O₈.     

Phase transition in copper(II) pyrovanadate

A new phase Cu₂V₂O₇ synthesized, exhibits phase transitions between 475°C and 500°C. These phase transitions are reversible with ease in contrast toα →β phase transition at 712°C of Cu₂V₂O₇ phase reported earlier. These phase transitions are identified by DTA technique and characterized by detailed XRD investigations at different temperatures. The crystal structures of these Cu₂V₂O₇ phases are related to either thortveitite (Sc₂Si₂O₇) type or a modification of it.     

Competitive adsorption of copper(II), cadmium(II), lead(II) and zinc(II) onto basic oxygen furnace slag

Polluted and contaminated water can often contain more than one heavy metal species. It is possible that the behavior of a particular metal species in a solution system will be affected by the presence of other metals. In this study, we have investigated the adsorption of Cd(II), Cu(II), Pb(II), and Zn(II) onto basic oxygen furnace slag (BOF slag) in single- and multi-element solution systems as a function of pH and concentration, in a background solution of 0.01M NaNO(3). In adsorption edge experiments, the pH was varied from 2.0 to 13.0 with total metal concentration 0.84mM in the single element system and 0.21mM each of Cd(II), Cu(II), Pb(II), and Zn(II) in the multi-element system. The value of pH(50) (the pH at which 50% adsorption occurs) was found to follow the sequence Zn>Cu>Pb>Cd in single-element systems, but Pb>Cu>Zn>Cd in the multi-element system. Adsorption isotherms at pH 6.0 in the multi-element systems showed that there is competition among various metals for adsorption sites on BOF slag. The adsorption and potentiometric titrations data for various slag-metal systems were modeled using an extended constant-capacitance surface complexation model that assumed an ion-exchange process below pH 6.5 and the formation of inner-sphere surface complexes at higher pH. Inner-sphere complexation was more dominant for the Cu(II), Pb(II) and Zn(II) systems.     

Crystal growth of caesium tin(II) trichloro-bromides

Crystals of compounds occurring in the solid solution range CsSnBr₃-CsSnCl₃ have been prepared by pulling from the melt and by Bridgman growth. The materials show a consistent change in colour and electrical resistivity from the black metallic conductor CsSnBr₃ to the bright yellow CsSnCl₃. The as-grown compounds undergo various structure changes from the cubic, high temperature form to lower symmetry forms on standing. These changes have been followed by DTA; they are also apparent as colour changes. X-ray examination indicates that the compounds react with atmospheric moisture to form monohydrates. The products showed some differences in their structural stability from powders of the same composition precipitated from solution. These differences are attributed to particle size effects analogous to those encountered in ferroelectric perovskites.     

Determination of copper(II) by displacement substoichiometric extraction with radiolabeled cobalt(II)

A substoichiometric radiochemical displacement technique has been employed for the quantification of trace amounts of copper from complex matrices. The procedure is based on higher stability of copper bipyridine complex compared to its cobalt analog, which leads to the displacement of spiked (⁶⁰Co) cobalt from its bipyridine complex in n-butanol by Cu(II). The amount of labeled cobalt stripped back into the aqueous phase is proportional to the amount of copper incorporated into the organic phase and is monitored for the quantitative estimation of copper. The interferences from various allied ions were critically examined. The proposed method has been successfully employed for the estimation of copper from various certified alloys.     

Studies on copper(II)- and zinc(II)-mixed ligand complexes of humic acid

Interactions between humic acid (HA), extracted from Brazilian peat soil, and cations of copper(II) and zinc(II) have been examined by infrared spectroscopy, and electrochemical and thermogravimetric analyses. Spectral studies revealed that the interaction with metals occurred mainly at the carboxylic acid groups of HA. The stability constants of HA complexes formed with Cu(2+) and Zn(2+) were found, by square wave voltammetry and application of the Lingane model, to be 8.93 x 10(10) and 2.92 x 10(2), respectively. Thermal analysis indicated that the stability of HA was increased by the presence of divalent cations of copper and zinc.     

Synthesis and properties of a copper(I) cobalt(II) double sulfite

The Pourbaix diagrams of the Cu–H₂SO₄–H₂O and Co–H₂SO₄–H₂O systems have been refined and the stability regions of sulfite phases in the diagrams have been identified. Phase diagrams of copper(I) copper( II) and copper(I) cobalt(II) double sulfites have been mapped out. The double sulfites Cu₂SO₃ · СuSO₃ and Cu₂SO₃ · СoSO₃ have been isolated from an aqueous solution saturated with sulfur dioxide. We have obtained electron paramagnetic resonance spectra of the double sulfite Cu₂SO₃ · СoSO₃ and characterized it by X-ray diffraction, IR spectroscopy, particle size analysis, and thermogravimetry. A foundation has been laid for the thermodynamic prediction of the synthesis of the Cu₂SO₃ · MSO₃ (M = Cu, Co) double sulfites.     

Development of a cloud point extraction-spectrofluorimetric method for trace copper(II) determination in water samples and parenteral solutions

A simple and efficient cloud point extraction-spectrofluorimetric method for the determination of copper(II) in different samples has been proposed. The procedure is based on the oxidation of thiamine with copper(II) to form highly fluorescent thiochrome, its extraction to Triton X-114 micelles and spectrofluorimetric determination. The variables affecting the analytical performance were studied and optimized. The calibration graphs using the preconcentration system for copper were linear over the range 1.0-250 ng ml-1 with limit of detection of 0.29 ng ml-1. Relative standard deviation for five replicate determinations of copper at 100 ng ml-1 concentration level was 2.12%. Average recoveries between 94 and 105% were obtained for spiked samples. The method has been applied to water samples and parenteral solutions and the amounts of copper found are very similar to those obtained by a standard method.     

Temperature and structure effects on the electrical conductivity properties of some azo compounds and their copper(II) complexes

The electrical conductivity of some 5-(m-substituted phenylazo) barbituric acid derivatives as well as their copper(II) complexes has been measured in the temperature range 297 to 443 K. The results revealed semiconducting properties for these systems. The conductivity curves in most cases gave two different activation energies. Both the structure of the ligand and the temperature played an effective role in the conduction process. Empirical equations correlating the activation energy to the conductivity are given. The mobility was calculated and a hopping model is proposed to explain the conduction process.     

Adsorption of copper (II), chromium (III), nickel (II) and lead (II) ions from aqueous solutions by meranti sawdust

The present study proposed the use of meranti sawdust in the removal of Cu(II), Cr(III), Ni(II) and Pb(II) ions from synthetic aqueous solutions. Batch adsorption studies showed that meranti sawdust was able to adsorb Cu(II), Cr(III), Ni(II) and Pb(II) ions from aqueous solutions in the concentration range 1–200 mg/L. The adsorption was favoured with maximum adsorption at pH 6, whereas the adsorption starts at pH 1 for all metal ions. The effects of contact time, initial concentration of metal ions, adsorbent dosage and temperature have been reported. The applicability of Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm was tried for the system to completely understand the adsorption isotherm processes. The adsorption kinetics tested with pseudo-first-order and pseudo-second-order models yielded high R² values from 0.850 to 0.932 and from 0.991 to 0.999, respectively. The meranti sawdust was found to be cost effective and has good efficiency to remove these toxic metal ions from aqueous solution.     

Biosorption of copper(II) and lead(II) from aqueous solution by chaff in a fixed-bed column

In this article, the ability of chaff to adsorb heavy metal ions from aqueous solution was investigated in a fixed-bed column. The effect of important parameters, such as the value of pH, the flow rate, the influent concentration of solution and the effect of coexistence ions, was studied. Also the adsorption/desorption recycles of chaff were shown, and the results indicated that chaff could be recycled to remove heavy metal ions. The Thomas model was applied to adsorption of copper and lead at different flow rate and different influent concentration to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. The model was found suitable for describing the biosorption process of the dynamic behavior of the chaff column. All the results suggested that chaff as adsorbent to removal heavy metal ions from solution prove efficient, and the rate of biosorption process is speedy. Furthermore, the efficiency of adsorption is high. When the flow rate was 3.6 ml min(-1) and the influent concentration of copper and lead was 14.82 mg l(-1) and 50.12 mg l(-1) respectively, the equilibrium adsorption biomass reached 1.98 mg g(-1) and 6.72 mg g(-1), respectively. The competitive adsorption for lead and copper was studied. Moreover the total adsorbing capability of chaff did not decrease when there were both copper(II) and lead(II) in solution.     

Structural and magnetic studies on copper succinate dihydrate single crystals

Single crystals of copper succinate dihydrate were grown in silica gel by slow diffusion of copper chloride to sodium metasilicate gel impregnated with succinic acid. The grown crystal was subjected to single crystal X-ray diffraction studies. In its structure each copper atom is penta co-ordinated to oxygen atoms of four succinate oxygens and oxygen of co-ordinated water molecule. The four bis-bidendate succinate anions form syn–syn bridges among two copper atoms to form a polymeric two-dimensional chain. From room temperature vibrating sample magnetometer (VSM) studies, the magnetic moment of the material is calculated as 1.35 Bohr magneton (BM), indicating anti-ferromagnetic interaction between copper atoms and can be explained as due to the orbital overlap of the bridging ligand and the two copper atoms in syn–syn orientation. A strong bonding of the magnetic orbital of equatorially oriented Cu atom on both sides of the exchange pathway (Cu–O-C-O–Cu) leads to the anti-ferromagnetic interaction.     

Effect of copper (II) chelate on photodegradation of poly (1-butene)

Photo-oxidative degradation of isotactic poly(1-butene) in the presence and absence of copper (II) bis-(1,3-diphenyl triazine-N-oxide) chelate has been studied, by measuring the weight average molecular weight, measuring changes in the carbonyl groups and by measuring changes in the hydroperoxide contents in the temperature range of 267 to 313 K using monochromatic light of wavelength 253.7 nm. The mechanism leading to the stabilization observed, resulting from the addition of chelate, is discussed.