Preconcentration of Cadmium with OP-10 Nonionic Surfactant Phases at the Cloud Point

The effect of the main parameters on the extraction of cadmium with carboxylic acids into the micellar phase of the OP-10 nonionic surfactant at the cloud point was studied. Conditions were found for the atomic absorption determination of cadmium in natural and waste waters using the micellar-extraction preconcentration with capric acid and n-octylamine into the surfactant phase.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 5, 2005, pp. 458–462.Original Russian Text Copyright © 2005 by Doroshchuk, Kulichenko.     

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30?µg?L^?1 and 2.6?µg?L^?1, respectively. A precision expressed as relative standard deviation (RSD, n?=?10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.     

Author Index to Volume 24

Abstract

The preparation of fairly monodisperse nanoparticles of zinc sulfide, cadmium sulfide, and lead chromate using a polymer–surfactant gel matrix as the template to resist particle clustering is been described. A hydrophobically modified polymer (chloride salt of N,N′‐dimethyl‐N‐methyl derivative of hydroxymethyl cellulose, JR 400) and a surfactant (sodium dodecyl sulfate, SDS) have been used to form the gel matrix. The nanodispersions formed in the gel at different precursor concentrations have been characterized by the TEM and SEM. Their UV‐visible and fluorescence spectra have been measured and analyzed. The band gaps and other characteristic properties of the nanomaterials have been estimated from the spectral data. A procedure for isolation of the products from the gel is described.     

Optimization of cadmium adsorption from aqueous solutions by functionalized graphene and the reversible magnetic recovery of the adsorbent using response surface methodology

Novel functionalized graphene adsorbent was prepared and characterized using different techniques. The prepared adsorbent was applied for the removal of cadmium ions from aqueous solution. A response surface methodology was used to evaluate the simple and combined effects of the various parameters, including adsorbent dosage, pH, and initial concentration. Under the optimal conditions, the cadmium removal performance of 70% was achieved. A good agreement between experimental and predicted data in this study was observed. The experimental results revealed of cadmium adsorption with high linearity follow Langmuir isotherm model with maximum adsorption capacity of 502 mg g^?1, and the adsorption data fitted well into pseudo‐second order model. Thermodynamic studies showed that adsorption process has exothermic and spontaneous nature. The recommended optimum conditions are: cadmium concentration of 970 mg L^?1, adsorbent dosage of 1 g L^?1, pH of 6.18, and T = 25 °C. The magnetic recovery of the adsorbent was performed using a magnetic surfactant to form a noncovalent magnetic functionalized graphene. After magnetic recovery of the adsorbent both components (adsorbent and magnetic surfactant) were recycled by tuning the surface charges through changing the pH of the solution. Desorption behavior studied using HNO₃ solution indicated that the adsorbent had the potential for reusability.     

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.     

Determination of cadmium in water samples by graphite furnace atomic absorption spectrometry after cloud point extraction

The formation of a complex with 2-(5-brom-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) and cloud point extraction have been applied to the preconcentration of cadmium followed by its determination by graphite furnace atomic absorption spectrometry (GFAAS) using octylphenoxypolyethoxyethanol (TritonX-114) as surfactant. The chemical variables affecting the separation were optimized. At pH 7.0, preconcentration of only 10 mL of sample in the presence of 0.05% TritonX-114 and 2.5 × 10⁻⁶ M 5-Br-PADAP enabled the detection of 0.04 μg/L cadmium. The enrichment factor was 21 for cadmium. The regression equation was A = 0.0439C(μg/L) + 7.2 × 10⁻³. The correlation coefficient was 0.9995. The precision for 10 replicate determinations at 10 μg/L Cd was 2.7% relative standard deviation (RSD). The proposed method has been applied to the determination of cadmium in water samples. The text was submitted by the authors in English.     

Investigation of sol-gel matrices containing crude metallothionein from <Emphasis Type="Italic">Scchizosaccharomyces pombe</Emphasis> for water treatment applications

The application of silica sol–gel particles containing crude metallothionein (MT) was investigated for cadmium removal from water. The metallothionein was first extracted from the yeast Scchizosaccharomyces pombe, and entrapped in the sol–gel matrices. Then sol–gel particles with the different sizes (ranging from 45 to 225 μm) were made. The effect of different flow rates as well as different particle sizes on adsorption of cadmium was investigated. The particle size has a greater effect on Cd adsorption than flow rate in the system studied. The breakthrough curves in the column were modeled using an empirical two parameter fixed-bed adsorption model. The model relates the changes of cadmium concentration in effluent to the standard deviation (σ) and characteristic of time (t ₀).     

K 0-prompt gamma ray activation analysis for estimation of boron and cadmium in aqueous solutions

K ₀-PGAA (prompt gamma activation analysis) has been used to estimate boron and cadmium contents in industrial and environmental materials from some different local areas as well as, samples from different locations in Burullus and Qarun Lakes. A high efficiency Compton background suppression gamma-ray spectrometry by anti-coincidence counting with a NaI(Tl) shield around a central HPGe detector for in beam PGAA using a ²⁵²Cf neutron source has been calibrated and described in this paper. The facility is principally designed for measurement of the prompt gamma-ray spectra obtained due to thermal neutron capture using 1951.14 keV gamma line of ³⁵Cl as the internal mono-standard comparator. A calibration curves were developed in which a set of boron and cadmium standards were tested and the count rate to boron and cadmium mass curves were determined. This set of boron and cadmium measurements was compared with a method for determining composition using K ₀-PGAA. Conventional prompt neutrons capture Gamma-ray results were in a good agreement with the data obtained by K ₀-PGAA method. Detection limits and self-shielding study are presented.     

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.     

Removal of cadmium ions using micellar-enhanced ultrafiltration with mixed anionic-nonionic surfactants

Micellar-enhanced ultrafiltration (MEUF) was used to remove cadmium ions from wastewater efficiently. In this study the nonionic surfactants polyoxyethyleneglycol dodecyl ether (Brij35) and polyoxyethylene octyl phenyl ether (TritonX-100) were for micellar-enhanced ultrafiltration to lower the dosage of the anionic surfactant sodium dodecyl sulfate (SDS). The surfactant critical micelle concentration (CMC) and the degree of micelle counterion binding were investigated. The effects of nonionic surfactant addition on the efficiency of cadmium removal, the residual quantities of surfactant, the permeate flux and the secondary membrane resistance were investigated. A comparison between MEUF with SDS and MEUF with mixed anionic–nonionic surfactants was undertaken. The results show that the addition of Brij35 or TritonX-100 reduced the CMC of SDS and the degree of counterion binding for the micelles. Due to these variations the Cd²⁺ rejection efficiency was at a maximum when the Brij35:SDS and the TritonX-100:SDS molar ratio was 0.5. The Cd²⁺ rejection efficiency in MEUF with SDS is higher than for MEUF with mixed surfactants when the total dose of surfactant is constant. The permeate flux of MEUF with SDS is higher than that for MEUF with mixed surfactants while the secondary resistance of MEUF with SDS is less than that of MEUF with mixed surfactants.     

Sorption of Cadmium from Aqueous Solutions at Different Temperatures by Mexican HEU-type Zeolite Rich Tuff

Many factors may affect the heavy metals sorption on natural zeolites among them the temperature, for this reason in this paper the cadmium retention behavior on Mexican zeolitic rich tuff as a function of temperature is considered. The kinetic and the isotherms were determined at 303, 318, and 333 K, the remaining cadmium in the solution samples was analyzed by atomic absorption spectrometry. The pseudo-second order rate constant, k, as well as the apparent diffusion coefficients were calculated from the cadmium uptake by the zeolitic rock as a function of the contact time and temperature, the highest amounts were found for the experiments done at 333 K. The maximum cadmium adsorption capacity by the zeolitic material was 12.2 mg Cd²⁺/g at 318 K corresponding to 20% of the effective ion exchange capacity of the Chihuahua zeolitic rock. In order to explain the cadmium sorption behavior different kinetics and isotherm models were considered.     

Distribution of Cd and Pb in a wetland ecosystem

Cadmium and lead contents in sediments, dominant species of plants (Phargmites aus-tralis andScripus mariquter), benthos (Helice tridens tientsinensis,Ilyoplax deschampsi, andBul-lacta exarata), and waders (Calidris ruficollis) on the Eastern End of Chongming Island were measured. The results showed that, for cadmium, there are clear stratification in the sediment of reclaimed area and bio-amplification in food chain. However, for lead, a phenomenon was different. The amplification factors (AFs) for cadmium of primary producers, primary consumers, and secondary consumers were 2.59–12.38, 0.09–8.44, and 51.1, respectively. For lead, AFs of primary producers, primary consumers and the top trophic layer were 0.29–2.62, 0.06–5.62, and 7.31, respectively. Each species of macrobenthos showed different strategies to cadmium and lead. Large-sized crabs accumulated more lead, while small-sized crabs and snails accumulated more cadmium. Waders had significantly highest AFs for cadmium and lead in the study. That is to say, bio-amplification of the food chain took place for cadmium and lead on the tidal flat with different AFs, and showed that different species have different strategies to a varies of heavy metal elements.

     

Determination of cadmium in rice and water by tungsten coil electrothermal vaporization-atomic fluorescence spectrometry and tungsten coil electrothermal atomic absorption spectrometry after cloud point extraction

In this work, the microsampling nature of tungsten coil electrothermal vaporization Ar/H₂ flame atomic fluorescence spectrometry (W-coil ETV-AFS) as well as tungsten coil electrothermal atomic absorption spectrometry (W-coil ET-AAS) was used with cloud point extraction (CPE) for the ultrasensitive determination of cadmium in rice and water samples. When the temperature of the extraction system is higher than the cloud point temperature of the selected surfactant Triton X-114, the complex of cadmium with dithizone can be quantitatively extracted into the surfactant-rich phase and subsequently separated from the bulk aqueous phase by centrifugation. The main factors affecting the CPE, such as concentration of Triton X-114 and dithizone, pH, equilibration temperature and incubation time, were optimized for the best extract efficiency. Under the optimal conditions, the limits of detection for cadmium by W-coil ETV-AFS and W-coil ET-AAS were 0.01 and 0.03 μg L⁻¹, with sensitivity enhancement factors of 152 and 93, respectively. The proposed methods were applied to the determination of cadmium in certified reference rice and water samples with analytical results in good agreement with certified values.     

Synthesis, 1 H, 13 C, 15 N, and 113 Cd NMR, ESI-TOF MS, Semiempirical MO (PM3), ab initio/HF and Cation/Anion Binding Studies of N-deoxycholyl-l-tryptophan

The synthesis, structural characterization, and cation/anion binding properties ofa new bile acid-amino acid conjugate, N-deoxycholyl-l-tryptophan, aredescribed. The structures of the ligand and its cadmium adduct at different pHconditions and various cadmium perchlorate concentrations were determined bymodern multinuclear magnetic resonance spectroscopic as well as ESI-TOF MStechniques. Also semiempirical PM3 and ab initio/HF molecular modellingstudies were performed. Based on ¹H,¹H NOESY measurementsN-deoxycholyl-l-tryptophan in alkaline conditions was found to appearin a bent conformation which was clearly different from the conformations in neutraland acidic solutions. According to molecular modelling in its minimum energy structurethe tryptophan backbone of the ligand was folded close to the deoxycholic acid skeletonand the structure was stabilized by an intramolecular hydrogen bond. The multinuclearmagnetic resonance experiments indicated that Cd²⁺-cation was bound with theligand in neutral and alkaline conditions while in acidic conditions protons block thebinding site. ESI-TOF MS revealed clearly a competition between sodium and cadmiumions, the ligand having a stronger affinity for sodium. Cadmium binding occurred onlywhen excess of cadmium was used. Further, ESI-TOF MS spectra showed that variouschlorine oxyanions originated from perchlorate anion formed together with cationsdifferent adducts with the ligand.     

Chromatographic Properties of Metallothioneins on a Gel Permeation Column: Changes Induced by Replacement of Cadmium with Cuprous and Cupric Ions

Abstract

In vitro experiments were conducted to find whether or not a similar elution profile to rat kidney metallothionein with high copper content was obtained on a gel permeation column by replacement of cadmium and/or zinc in rat liver metallothionein with copper. Stepwise replacement of cadmium in rat liver metallothionein with cuprous ion did not cause any shifts of retention times from those of the original proteins on a gel permeation column (SW 3000 column). In contrast to cuprous ion, stepwise replacement of cadmium with cupric ion induced shifts of retention times to larger values than the original ones for the two isometallothioneins on a SW column. Replacement of zinc in zinc-thionein with cupric ion but not with cuprous ion caused a retardation of elution volume on a Sephadex G-75 column. The decreases of cadmium peaks were accompanied by the increases of copper peaks in the case of replacement of cadmium in metallothionein with cuprous ion. Although stepwise decreases of cadmium peaks were observed by the replacement of cadmium in metallothionein with cupric ion, concomitant increases of copper peaks were not observed. Although the relative peak heights of isometallothionein peaks were different from those of rat kidney metallothionein, the third peak with the same retention time as that of rat kidney metallothionein was observed for the replacement of cadmium with cupric but not with cuprous ion.     

Determination of nanogram amounts of cadmium in water by electrothermal atomic absorption spectrometry after flotation separation

A method is described for the flotation an determination of ng-levels of cadmium in water. Cadmium in a 1-l sample of water is coprecipitated with hydrated zirconium oxide at pH 9.1 ± 0.1. The precipitate is floated with the aid of a surfactant solution and small air bubbles, separated and dissolved in dilute hydrochloric acid. The cadmium content is determined by electrothermal atomic absorption spectrophotometry. The method is applied to the determination of ng l^?1 levels of cadmium in fresh water. The time required for preconcentration of cadmium from a 1-l sample is 20 min per sample, after 20 min stirring.     

Comparison of Extraction Techniques and Surfactants for the Isolation of Total Polyphenols and Phlorotannins from the Brown Algae Lobophora variegata

Abstract

Surfactant-mediated extraction (SME), pressurized liquid extraction (PLE), and enzyme-assisted extraction (EAE) have been compared to improve the isolation of phlorotannins from the brown algae Lobophora variegata. Enzymatic treatment with Alcalase 2.4?L FG, Carezyme 4500?L, protease from Streptomyces griseus, pectinase from Aspergillus niger, Celluclast 1.5?L, protease from Bacillus licheniformis; surfactant extraction with triacetin and guaiacol and PLE with ethanol:water as extracting solvent, have been studied in terms of total phenolic content by the Folin–Ciocalteu method and total phlorotannin content using the DMBA assay. The results showed that SME yields the highest amount of phenols and phlorotannins by using food grade guaiacol as the surfactant. An extraction protocol was developed to maximize the amount of extract obtained from L. variegata. The effects of various parameters such as the type of surfactant, efficacy of surfactant, and optimum pH, on the extraction efficiency of polyphenols were examined. The simultaneous use of the enzyme and surfactant was also investigated. However, a synergistic effect between the enzymes and the surfactant for the extraction of polyphenols has not been observed. Considering total phenols and total phlorotannins in the extract, the extraction yield were obtained for total phenols as SME?>?EAE?>?PLE and for total phlorotannins as SME?>?PLE?>?EAE.     

Determination of Ultratrace Amounts of Copper and Cadmium in Seawater by Graphite Furnace Atomic Absorption Spectrometry with Flow-Injection Semi On-line Preconcentration

Methods are described for the determination of ultratrace amounts of copper and cadmium in seawater by graphite furnace atomic absorption spectrometry with flow-injection, microcolumn preconcentration. A new type of C₁₈ column loaded with sodium diethyldithiocarbamate (sodium-DDC) was used to extract copper and cadmium from seawater as the DDC chelates. The analytical effects of the pH of the mixture of the sample and sodium-DDC solutions and the concentration of the chelating reagent were studied. Sodium-DDC-loaded columns and unloaded C₁₈ columns with different shapes and volumes were compared. To determine copper in seawater, a simple aqueous calibration was made with a mixture of palladium and magnesium nitrate as a matrix modifier, while for cadmium no matrix modifier was necessary. This method required only small seawater volumes, 600 and 400 μl for the determination of copper and cadmium respectively, with preconcentration factors of 15-fold for copper and 10-fold for cadmium. Detection limits for the preconcentration of aqueous solutions of copper and cadmium were 0.024 and 0.004 μg liter⁻¹ (3σ), respectively. Results for determinations of copper and cadmium in National Research Council of Canada, CASS-2, Nearshore Seawater Reference Material showed no significant differences between the certified values and the measured values, based on Student′s t test at the 95% confidence level. The relative standard deviations of the various measurements varied between 2 and 8%.     

Determination of Trace Amounts of Cadmium with p-Acetyl-Benzenediazoaminoazobenzene by Primary–Secondary Wavelength Spectrophotometry

The reaction between Cd²⁺and a chromogenic agent, p-acetylbenzenediazoaminoazobenzene (p-ABAA) at pH 12.5 is sensitive and selective in the presence of triethanolamine and citrate. The solubilization and sensitization of the OP emulsifier (nonionic surfactant) was observed in the above reaction. Because the absorption of excess p-ABAA interferes with the absorption of the complex, primary–secondary wavelength spectrophotometry (PSWS) was used instead of the single-wavelength method in the determination of trace amounts of cadmium. Results showed that this method gave out a higher precision and better accuracy than the single-wavelength method, because two wavelengths that are located at the peak absorption and the valley absorption of the reaction solution were used simultaneously. By analyzing samples, the relative standard deviations were less than 8% and the recovery between 96.5 and 111%.     

Formation and Stability of Cadmium(II)/Phytate Complexes by Different Electrochemical Techniques. Critical Analysis of Results

In the present work the stability constants of various cadmium(II)/phytate (Phy) species were determined at T=298.15 K in NaNO₃(aq) at I=0.1 mol⋅L⁻¹ by DP-ASV (Differential Pulse Anodic Stripping Voltammetry) and by potentiometric titrations using an ISE-Cd²⁺. Cyclic voltammograms were also recorded to check the electrochemical behavior of cadmium in the presence of phytate. The results were analyzed together with previous data determined by ISE-H⁺ measurements. Data obtained were used to provide an exhaustive speciation scheme for the phytate/cadmium(II) system at different conditions, as well as a comprehensive representation of the binding ability of phytate toward cadmium(II). Different pL₅₀ values {a previously proposed empirical parameter, expressed as −log ₁₀ C _Phy, where C _Phy is the total phytate concentration necessary to bind 50% cadmium(II)} were also calculated by modeling its dependence on pH.