Adsorptive bubble separation of zinc and cadmium cations in presence of ferric and aluminum hydroxides

The adsorptive bubble separation of zinc and cadmium cations from solution in the presence of ferric and aluminum hydroxides was carried out by means of Tween 80 (nonionic surfactant), and sodium laurate and stearate (anionic surfactants). The mechanism of metal removal is different depending on the nature of the surfactant used. The removal of zinc cations by adsorbing colloid flotation is higher than that of cadmium cations. It increases with increases in the amount of hydroxide precipitate and the concentration of Tween 80. The removal of zinc cations by ion flotation is lower than that of cadmium cations. It does not change with increases in the hydroxide amount. It increases, however, with increased sodium laurate or stearate concentration. Both separation methods turned out to be helpful for studying both the solution's structure and the interactions at the solution-solid interface.     

Indirect voltammetric determination of total surfactants in waters

The effect of anionic, cationic, and nonionic surfactants on anodic peaks of metals in their voltammetric determination was studied. It was shown that the total of synthetic surfactants in waters can be determined. Neonol was chosen as a reference substance for the determination of synthetic surfactants in solution; zinc and cadmium were chosen as reference elements     

The method of appearing solvent: Extraction of metal ions from aqueous solutions into in situ forming ionic liquid

The simultaneous dissolution of tetraoctylammonium bromide and sodium N-lauroyl sarcosinate in water leads to the in situ formation of a water-immiscible ionic liquid, tetraoctylammonium N-lauroyl sarcosinate. The new phase formed can extract cadmium, cobalt, copper, nickel, lead, and zinc ions from aqueous solution in the presence of 4-(2-pyridylazo)resorcinol (PAR), while it can extract cadmium ions in the absence of PAR.     

Spectrophotometric determination of micro amounts of mercury,cadmium, and zinc by stepwise extraction with tribenzylamine

A rapid spectrophotometric method has been developed for the stepwise determination for mercury, cadmium, and zinc in mixtures. Optimal conditions have been established for the extraction efficiency of cadmium and mercury with a chloroform solution of tribenzylamine pre-equilibrated with hydrobromic acid. After addition of dithizone solution to the organic layers the absorbance at 490 nm or 510 nm is measured for mercury or cadmium, respectively. Even when the ratio of mercury, cadmium, and zinc is 10^-1 : 1 : 10^-5 , the metals can be determined successively.     

Micellar-enhanced ultrafiltration of cadmium ions with anionic–nonionic surfactants

Micellar-enhanced ultrafiltration (MEUF), a surfactant-based separation process, is promising in removing multivalent metal ions from aqueous solutions. The micellar-enhanced ultrafiltration of cadmium from aqueous solution was studied in systems of anionic surfactant and mixed anionic/nonionic surfactants. The micelle sizes and zeta potentials were investigated by dynamic light scattering measurements. The effects of feed surfactant concentration, cadmium concentration and the molar ratio of nonionic surfactants to sodium dodecyl sulfate (SDS) on the cadmium removal efficiency, the rejection of SDS and nonionic surfactants and the permeate flux were investigated. The rejection efficiencies of cadmium in the MEUF operation were enhanced with higher SDS concentration and moderate Cd concentration. When SDS concentration was fixed at 3 mM, the optimal ranges of the molar ratios of nonionic surfactants to SDS for the removal of cadmium were 0.4–0.7 for Brij 35 and 0.5–0.7 for Triton X-100, respectively. With the addition of nonionic surfactants, the SDS dosage and the SDS concentration in the permeate were reduced efficiently.     

镉基体中微量锌的富集与分离研究

提出了一种用于富集分离镉基体中的微量锌的分离体系,研究了从镉基体中富集分离微量锌的可行性——采用二安替比林甲烷(DAM)作为络合剂,与硫氰酸铵、锌在盐酸介质中形成三元离子缔合物,用三氯甲烷作为萃取剂,最后用氨水作为反萃剂将有机相中的锌洗脱出来与镉分离。试验发现,当15%的硫氰酸铵用量为1.5mL,DAM的用量为1.5mL,加入20mL4mol/L的盐酸时,用20mL的三氯甲烷萃取两次,10mL1:3的氨水反萃两次,锌的回收率达到95%以上,相对误差小于0.5%。     

Glucose oxidase inhibition in poly(neutral red) mediated enzyme biosensors for heavy metal determination

A biosensor for the determination of heavy metal cations based on glucose oxidase enzymatic inhibition has been developed. The biosensor was assembled on carbon film electrode supports with glucose oxidase immobilised by cross-linking with glutaraldehyde on top of a film of poly(neutral red) as redox mediator, prepared by electropolymerisation. The biosensor was used to determine the metallic cations, cadmium, copper, lead and zinc in the presence of chosen amounts of glucose. The detection limits were found to be 1 μg L^?1 for cadmium, 6 μg L^?1 for copper, 3 μg L^?1 for lead and 9 μg L^?1 for zinc. Inhibition constants were determined by using the Dixon plot, and the type of inhibition induced by the metallic cations was evaluated from Cornish-Bowden plots plus Dixon plots, it being found that the inhibition is reversible and competitive for cadmium, mixed for copper and lead and uncompetitive for zinc. Copper-inhibited glucose oxidase to a greater extent followed by cadmium, lead and zinc. Regeneration of the glucose oxidase response was studied by using Ethylene diamine tetracetic acid metal-chelating agent and the nonionic surfactant Triton X-100. The suitability of the biosensor for determination in foodstuffs or beverages which contain trace concentrations of metals was investigated by performing recovery tests in commercial milk samples.     

Kinetically controlled separation of cadmium(II) from zinc(II) with dithizone in the presence of nitrilotriacetic acid.

The extraction rates of cadmium(II) and zinc(II) with dithizone (H2dz) in the presence of nitrilotriacetic acid (NTA) were measured, and the possible kinetic separation of cadmium(II) from zinc(II) was investigated. Upon the addition of NTA, the difference in the extraction rate between cadmium(II) and zinc(II) became large. Based on the observed rate constant under the condition [NTA] = 1 x 10(-2) mol dm-3, [H2dz]org = 1 x 10(-3) mol dm-3, and pH = 7.0, the shaking time required for the quantitative separation of cadmium(II) from zinc(II) was calculated to be between 326 and 995 s. The experimental results agreed with the prediction, and the quantitative separation of cadmium(II) from zinc(II) was performed within the above-mentioned range of shaking times.     

Spectrophotometric and spectrofluorometric determination of zinc and cadmium with 2,2'-pyridil bis(2-quinolylhydrazone)

The chelating ligand, 2,2'-pyridil bis(2-quinolylhydrazone), has been used for the spectrophotometric determination of zinc and cadmium in synthetic samples. The molar absorptivities of these metal complexes in 80% ethanol-water solution at pH 8 were found to be 4.60 x 10(4) and 5.10 x 10(4) 1.mole(-1).cm(-1) for zinc and cadmium respectively. Beer's law was obeyed for metal-ion concentrations between 1.0 x 10(-6) and 2.5 x 10(-5)M. The limits of detection were found to be 52 and 79 ng ml for zinc and cadmium respectively. The complexes fluoresced in 80% ethanol-water at pH 8 for zinc and at pH 10 for cadmium. The linear range for fluorescence as a function of metal-ion concentration was found to be 5 x 10(-7)-5 x 10(-6)M for both zinc and cadmium. Transition-metal ions interfere severely with both the spectrophotometric and fluorimetric determinations, and must be removed beforehand. An ion-exchange procedure is suitable for this.     

Determination of silver, antimony, bismuth, copper, cadmium and indium in ores, concentrates and related materials by atomic-absorption spectrophotometry after methyl isobutyl ketone extraction as iodides

Methods for determining ~ 0.2 mug g or more of silver and cadmium, ~ 0.5 mug g or more of copper and ~ 5 mug g or more of antimony, bismuth and indium in ores, concentrates and related materials are described. After sample decomposition and recovery of antimony and bismuth retained by lead and calcium sulphates, by co-precipitation with hydrous ferric oxide at pH 6.20 +/- 0.05, iron(III) is reduced to iron(II) with ascorbic acid, and antimony, bismuth, copper, cadmium and indium are separated from the remaining matrix elements by a single methyl isobutyl ketone extraction of their iodides from ~2M sulphuric acid-0.1M potassium iodide. The extract is washed with a sulphuric acid-potassium iodide solution of the same composition to remove residual iron and co-extracted zinc, and the extracted elements are stripped from the extract with 20% v v nitric acid-20% v v hydrogen peroxide. Alternatively, after the removal of lead sulphate by filtration, silver, copper, cadmium and indium can be extracted under the same conditions and stripped with 40% v v nitric acid-25% v v hydrochloric acid. The strip solutions are treated with sulphuric and perchloric acids and ultimately evaporated to dry ness. The individual elements are determined in a 24% v v hydrochloric acid medium containing 1000 mug of potassium per ml by atomic-absorption spectrophotometry with an air-acetylene flame. Tin, arsenic and molybdenum are not co-extracted under the conditions above. Results obtained for silver, antimony, bismuth and indium in some Canadian certified reference materials by these methods are compared with those obtained earlier by previously published methods.     

Kinetic effect of zinc(II) and cadmium(II) ions on configurational inversion of deltaLLL-fac(S)-tris(L-cysteinato-N,S)cobalt(III) complex.

It has been confirmed from circular dichroism (CD) spectral changes of aqueous solutions of deltaLLL-fac(S)-[Co(L-cys-N,S)3]3- that the absolute configurational inversion to the ALLL isomer is remarkably accelerated by zinc(II), while it is retarded by cadmium(II). In the diluted solutions of these metal ions containing excess deltaLLL-fac(S)-[Co(L-cys-N,S)3]3-, the observed inversion rate constant linearly depends on the zinc(II) concentration with an intercept, while it is not affected by the cadmium(II) concentration. The kinetic behavior has been explained by difference between zinc(II)- and cadmium(II)-interactions with lone pairs on sulfur donor atoms of fac(S)-[Co(L-cys-N,S)3]3-. It has also been proposed that concentrations of zinc(II) and cadmium(II) can be simultaneously determined by the kinetic measurements.     

Electrothermal atomic absorption spectrometric determination of ng g-1 levels of cadmium in bone after dithizone extractions

After removal of lipid and acid digestion of bone samples, cadmium is separated from the matrix by two extractions with dithizone in carbon tetrachloride. The first extraction at pH 3–3.5 removes cadmium from the matrix; the second extraction, at pH 8.5 in the presence of 2-hydroxyethylethylenediaminetriacetic acid, is needed to prevent suppression of the cadmium signal by zinc. Cadmium is finally measured in the back-extract into 0.24 M hydrochloric acid. Less than 10 ng g^-1 cadmium in fresh bone can be determined within a relative standard deviation of 10%.     

Determination of cadmium, copper, lead and zinc in water samples by flame atomic absorption spectrometry after cloud point extraction

Cloud point extraction (CPE) has been used for the simultaneous pre-concentration of cadmium, copper, lead and zinc after the formation of a complex with 1-(2-thiazolylazo)-2-naphthol (TAN), and later analysis by flame atomic absorption spectrometry (FAAS) using octylphenoxypolyethoxyethanol (Triton X-114) as surfactant. The chemical variables affecting the separation phase and the viscosity affecting the detection process were optimized. At pH 8.6, pre-concentration of only 50 ml of sample in the presence of 0.05% Triton X-114 and 2×10⁻⁵ mol l⁻¹ TAN permitted the detection of 0.099, 0.27, 1.1 and 0.095 ng ml⁻¹ cadmium, copper, lead and zinc, respectively. The enhancement factors were 57.7, 64.3, 55.6 and 63.7 for cadmium, copper, lead and zinc, respectively. The proposed method has been applied to the determination of cadmium, copper, lead and zinc in water samples and a standard reference material (SRM).     

Determination of cadmium and bismuth in high-purity zinc metal by inductively coupled plasma mass spectrometry with on-line matrix separation

Traces of cadmium and bismuth in high-purity zinc metal were determined by inductively coupled plasma mass spectrometry (ICP-MS) in combination with flow injection (FI) on-line matrix separation (FI-ICP-MS). The anion-exchange separation method of the potassium iodide (KI) system was applied to the separation of the analytes from the matrix zinc. The analytes, cadmium and bismuth, were adsorbed on the anion-exchange (BIO. RAD AG1-X8) mini-column (1.0 mm i.d.x 100 mm bed length), while the matrix zinc can be completely removed from the anion-exchange resin. The analytes were eluted by 2 mol/l HNO(3) and directly introduced into the ICP-MS. The detection limits (D.L.) obtained by using a single injection (350 microl) were 0.81 and 0.075 ng g(-1) for cadmium and bismuth, respectively. In the case of multi-injection concentration onto the anion-exchange mini-column (five injections 350 microl each), the detection limits could be improved to 0.16 and 0.014 ng g(-1) for cadmium and bismuth, respectively. The reproducibilities of the single injection and the multi-injection method were satisfactory with a relative standard deviation of less than 5% (at the 10 and 1 ng ml(-1) level for the single injection and the multi-injection method, respectively). The method was successfully applied to the determination of trace impurities in four samples of high-purity zinc metal (7 nines grade) and three standard reference materials of high-purity unalloyed zinc samples (from NIST).     

Anilinepropylsilica xerogel used as a selective Cu (II) adsorbent in aqueous solution

The metal ion adsorption properties of the microporous hybrid anilinepropylsilica xerogel were studied using divalent copper, zinc, and cadmium ions in aqueous solutions in concentrations ranging from 10(-4) up to 5x10(-3) moll(-1). At low concentrations the surface of the solid phase presents selectivity for Cu (II), even in competitive conditions. This preferential sorption ability for copper in relation to zinc and cadmium ions was interpreted by considering the xerogel morphology.     

Kinetic of Leaching of Cadmium and Zinc from Their Oxides and Hydroxides

The rotating disc method was applied to study the kinetics of leaching of zinc and cadmium from their oxides and hydroxides by sulfuric acid at pH 2-5, temperature of 288-313 K, and disc rotation velocities of 300-3600 rpm. The kinetic regions of the topochemical processes of zinc and cadmium leaching were revealed.     

直读光谱法测定析出锌中铅、铜、铁、镉、锡、铝的含量

研究了湿法冶炼产出的析出锌,经过冲床冲压脱模、马弗炉高温熔化、模具浇铸成型、车床切削等过程,于直读光谱仪上测定析出锌中铅、铜、铁、镉、锡、铝含量的方法。通过实验确认了仪器的工作条件、熔样器皿、熔样温度、析出锌取样位置,并对熔样铸锭后铅、铜、铁、镉、锡、铝的偏析情况进行了分析,铅最大偏差达到30%,经玻璃棒搅动后保温,铅的偏差消除,拟定了直读光谱法测定析出锌中铅、铜、铁、镉、锡、铝含量的方法,应用后可以快速出具分析结果,指导生产。     

Determination of cadmium by differentialn pulse anodic-stripping voltammetry after salting-out extraction into acetonitrile

A selective and specific method is presented for anodic-stripping voltammetric determination of cadmium after extraction with 0.1Mtetrabutylammonium iodide solution in acetonitrile from aqueous ammonium sulphate solutions. The detection limit of this method is 0.2 ng ml (in the acetonitrile extract). Interference from matrices or large amounts of elements reduced at more positive potentials can be eliminated by prior extraction. The method has been applied to trace analysis for cadmium in zinc, lead and indium metals, and some inorganic salts.     

Reactions of laser-ablated zinc and cadmium atoms with CO: infrared spectra of the Zn(CO)x (x = 1-3), CdCO-, and Cd(CO)2 molecules in solid neon

Reactions of laser-ablated zinc and cadmium atoms with carbon monoxide molecules in solid neon have been investigated using matrix-isolation infrared spectroscopy. Based on the isotopic substitution, absorptions at 1852.2, 1901.9, 1945.9, and 1995.2 cm(-1) are assigned to the C-O stretching vibrations of the ZnCO, Zn(CO)(2), and Zn(CO)(3) molecules. Absorptions at 1735.8, 1961.3, and 2035.7 cm(-1) are assigned to the C-O stretching vibrations of the CdCO(-) and Cd(CO)(2) molecules. In contrast with the previous argon experiments, more species and more valuable information about the reaction of zinc and cadmium atoms with CO have been obtained in solid neon. Density functional theory calculations have been performed on these zinc and cadmium carbonyls. The agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts substantiates the identification of these carbonyls from the matrix infrared spectrum. The present experiments also reveal that zinc is more reactive with CO than cadmium.     

Separation and determination of cadmium and zinc as their thenoyltrifluoroacetone complexes with dibenzo-18-crown-6 by means of synergistic extraction and atomic absorption spectrometry

 A new method for the separation and determination of trace amounts of cadmium and zinc in water as their thenoyltrifluoroacetone (TTA) complexes with dibenzo-18-crown-6 (DB18C6) in o-dichlorobenzene has been established by means of synergistic extraction and back-extraction combined with atomic absorption spectrometry. The effect of various factors (synergism with TTA and DB18C6, shaking time, composition of the extracted species, and mutual separation etc.) on the extraction and back-extraction of cadmium and zinc has been in- vestigated. When the mixtures were extracted for 4 min at pH 4.9, only zinc was extracted quantitatively, whereas cadmium remained in the aqueous phase. After the phases were separated, cadmium was again extracted quantitatively at pH 7.5. Then, the two phases were each shaken with 0.05–0.1 mol/l HCl in order to back-extract cadmium and zinc from the organic phases; the ions were determined individually by atomic absorption spectrometry. In the process cadmium and zinc TTA chelates in o-dichlorobenzene form stable adducts with DB18C6 (Cd(TTA)₂ ⋅ nDB18C6 and Zn(TTA)₂ ⋅ nDB18C6, n=0∼2). The stability constants (βn) of the adducts determined by means of the curve fitting method were log β₁=4.62 and log β₂=6.74 for cadmium, and log β₁=3.48 and log β₂=5.18 for zinc. Received: 8 September 1995/Revised: 22 January 1996/Accepted: 24 January 1996