Cadmium Stripping Research Articles

Studying of the effect of many parameters on a bulk liquid membrane and its opposition in Cd(II) removal from wastewater

Because of their tendency to accumulate in the body and their highly toxic potential, heavy metal pollution is becoming one of the main problems globally. The presented study examined the likelihood of eliminating heavy metals by means of the Bulk Liquid Membrane (BLM) method, which is a tool of high importance in various applications of such type. BLM is a simple type of liquid membrane which is showing excellent membrane stability yet insignificant solute fluxes. Therefore, this study outlines the BLM’s membrane resistance in removing heavy metals and recovery from the waste-waters. The cadmium (Cd) ions are fully prepared from the acidic aqueous solutions in this study with the use of the BLM. With regard to stirred transfer cell type, an experimental research has examined the recovery and extraction of Cd ions from synthetic wastewater solution via carrier Tri-butyl-phosphate TBP [C12H27O4P] with the use of BLM as an approach of separation. The impact of some parameters such as feed and stripping stirring speed, carrier concentration, membrane stirring speed, initial feed concentration, temperature, feed, and stripping phase pH is assessed for Cd removal. At pH 4 for feed, pH 10 for strip, 10 %(v/v) carrier concentration, 2 ppm initial concentration, 150 rpm,(S:F) = (1:1) in toluene, and the room temperature the maximal efficiency of extraction and stripping of cadmium (II) metal ions was 82 % and 93 %.

Extraction and separation of Cd(II) and Ni(II) with salts of Cyanex 301 and amines

The extraction of cadmium from sulfuric acid solutions and its separation from nickel with salts of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) and amines was studied. The data obtained show that extractants based on Cyanex 301 and Quaternary ammonium bases are most suitable for this since it is possible to extract cadmium in the form of sulfates and bisulfates as well as stripping metal from the organic phase. For deep extraction of cadmium from sulfate solutions in this system, 1–2 stages of extraction are sufficient. At this stage, the separation coefficient of cadmium and nickel βCd/Ni reaches values > 106, and the distribution coefficient of cadmium reaches almost 104. Cadmium stripping is achieved by treating the organic phase with an ammonia solution containing ammonia more than 4 mol/L. The process can be used in the processing of cadmium–nickel batteries.

Stripping voltammetry at graphene oxide: The negative effect of carbonaceous debris

The synthesis of graphene oxide through the chemical exfoliation of graphite by oxidative treatment always gives rise to a significant amount of polyaromatic byproducts, which are usually termed as oxidative carbonaceous debris. The carbonaceous debris is strongly adsorbed on the surface of graphene oxide, which inevitably affects its physical and chemical properties. Herein, we investigate the influence of the adsorbed carbonaceous debris on the stripping analysis of cadmium at graphene oxide electrode. Voltammetric responses and analytical performances have been achieved and systematically compared in connection with the anodic stripping of cadmium performed at the graphene oxide electrodes in the presence and absence of the carbonaceous debris. The results suggested that the adsorption of the carbonaceous debris dramatically restricted the deposition of cadmium metal and lowered the stripping analytical performances of cadmium ions.

Deciphering lead and cadmium stripping peaks for porous antimony deposited electrodes

AbstractCadmium and lead are generally taken as model heavy metal ions in water to scale the detection limit of various electrode sensors, using electrochemical sensing techniques. These ions interact with the electrochemically deposited antimony electrodes depending on the diffusion limitations. The phenomenon acts differently for thein-situandex-situdeposition as well as for porous and non-porous electrodes. A method has been adopted in this study to discourage the stripping and deposition of the working ions (antimony) to understand the principle of heavy metal ion detection. X-ray photoelectron spectroscopy (XPS) technique was used to establish the interaction between the working and dissolved ions. In addition to the distinct peaks for each analyte, researchers also observed a shoulder peak. A possible reason for the presence of this peak was provided. Different electrochemical tests were performed to ascertain the theory on the basis of the experimental observations.

Anodic stripping voltammetric determination of cadmium using a “mercury free” indium film electrode

In this work, the determination of cadmium has been attempted using an indium film electrode in the presence of bromide ions as an additive, for the first time. The electrode was prepared in situ on a glassy carbon substrate and employed in combination with square wave anodic stripping voltammetry. The purpose of having bromide ions is to enhance the analytical value of cadmium detection. In the absence of bromide ions, cadmium stripping peaks coalesce with indium and it is difficult to resolve for analytical purposes. The addition of bromide ions strongly influences the peak separation, thanks to the complex-forming characteristics of cadmium with bromide ions. Several key operational parameters influencing the electroanalytical response of indium modified electrodes were examined and optimized, such as deposition potential, pH, bromide ion and indium concentration. The indium modified electrode exhibited well-defined, separated stripping signals and revealed good linear behavior in the examined concentration range from 1 to 25 ng ml(-1). The present method shows a low detection limit value of 0.36 ng ml(-1). These results suggest that the proposed electrode contributes to the wider applicability of electrochemical stripping techniques in connection with "mercury-free" electrodes.

Quantitative Voltammetry in Weakly Supported Media. Two Electron Transfer, Chronoamperometry of Electrodeposition and Stripping for Cadmium at Microhemispherical Mercury Electrodes

Double potential step chronoamperometry for the two-electron transfer amalgam-forming deposition and stripping of cadmium at a hemispherical mercury electrode in aqueous solution containing different concentrations of supporting electrolyte is compared with simulated results using the Nernst-Planck-Poisson system of equations. The latter were generated using an approximation of zero electric field at the interface [J. Phys. Chem. C 2008, 112, 13716−13728]; the approximation gives a good agreement between theory and experiment, so validating its use for the description of macroelectrode and microelectrode (but not nanoelectrode) problems involving low or negligible levels of supporting electrolyte.

CdTe nanocrystal-based electrochemical biosensor for the recognition of neutravidin by anodic stripping voltammetry at electrodeposited bismuth film

CdTe quantum dots (QDs)-based electrochemical sensor for recognition of neutravidin, as a model protein, using anodic stripping voltammetry at electrodeposited bismuth film is presented. This biosensor involves the immobilization of the captured QDs conjugates which was dissolved with 1 M HCl solution to release cadmium ions and metal components were quantified by anodic stripping voltammetry after a 3-min accumulation at −1.2 V on bismuth-film electrode (BiFE) of the biotin, served as recognition element, onto the gold surface in connection with a cysteamine self-assembled monolayer. The modification procedure was characterized by electrochemical impedance spectroscopy and atomic force microscopy. We exploit QDs as labels for amplifying signal output and monitoring the extent of competition process between CdTe-labeled neutravidin and the target neutravidin for the limited binding sites on biotin. As expected for the competitive mechanism, the recognition event thus yields distinct cadmium stripping voltammetric current peak, whose response decreases upon increasing the level of target neutravidin concentrations. Under optimal conditions, the voltammetric response is highly linear over the range of 0.5–100 ng L −1 neutravidin and the limit of detection is estimated to be 0.3 ng L −1 (5 nM). Unlike earlier two-step sandwich bioassays, the present protocol relies on a one-step competitive assay, which is more accurate and sensitive, showing great promise for rapid, simple and cost-effective analysis of protein.

Extraction of Cadmium from Phosphoric Acid Media by Di(2‐ethylhexyl) Dithiophosphoric Acid

Di(2‐ethylhexyl) dithiophosphoric acid (D2EHDTPA) was examined for cadmium removal from phosphoric acid solutions. High extraction performance was achieved. By means of slope and saturation methods, the stoichiometry of the complex was postulated. Both methods indicated the presence of anhydrous CdR2 as being the metallic extracted complex, HR denoting the D2EHDTPA molecule. The stripping of cadmium from the organic phase was ensured by aqueous solutions of HCl; quantitative stripping was achieved with either HCl (4 M) or an HCl‐NaCl mixture.

Investigation into cadmium embrittlement of landing gear wheel axles

There are two landing gear wheel axles, called, respectively, 1# and 2#. Axle 1# was not carried through cadmium stripping prior to stress annealing, and the repair process of axle 2# had cadmium stripping before stress relieving. In order to confirm if there is cadmium embrittlement in the landing gear wheel axles, a series of experimental analyses were carried through and some conclusions were obtained. There is no cadmium diffusion in 1# and 2# axles and risk of cadmium embrittlement can be excluded. High compressive stress exists on surface of 1# and 2# axles and shot peening is effective. Cadmium layer was oxidized approximately 0.35 μm from outer surface, but the oxidized layer has not attacked the base material. The prerequisites of cadmium embrittlement were studied. The three prerequisites of cadmium embrittlement are cadmium, a certain tensile stress and a certain temperature. Disappearance of any one of the prerequisites can avoid cadmium embrittlement as verified by our experiments.

Sonoelectroanalysis: Anodic Stripping Voltammetric Determination of Cadmium in Whole Human Blood

AbstractThe quantitative detection of cadmium in human blood is shown to be possible by anodic stripping voltammetry under conditions of insonation. An immersion horn probe is introduced into a thermostatted conventional three‐electrode cell opposite a Nafion‐coated mercury plated glassy carbon electrode. The enhanced mass transport associated with power ultrasound yields efficient preconcentration of the cadmium before it is detected using anodic differential‐pulse stripping voltammetry. Insonation further offers the crucial benefits of first surface activation and cleaning, helping to prevent electrode fouling by the organic components in blood and second fully equilibrating “free” and “bound” Cd2+ ions in the complex matrix. Acoustic streaming and cavitation promote the mass transport of cadmium to the surface of electrode, facilitating measurements in solutions of low cadmium concentration, where “silent” measurements fail to yield an analytical signal. The system is calibrated using standard micro additions of cadmium to give the total amount of cadmium in blood. The calibration plot, showing the dependence of the cadmium stripping peak height on cadmium concentration in 1 : 50 diluted blood samples, was linear in the range 1×10−10 M to 4×10−9 M Cd2+. The values of cadmium concentration obtained using sonoelectroanalytical methodology were compared with the results obtained by independent atomic absorption spectroscopy (AAS) measurements and good agreement was found.

Electrochemical Detection of Trace Concentrations of Cadmium and Lead with a Boron‐Doped Diamond Electrode: Effect of KCl and KNO3 Electrolytes, Interferences and Measurement in River Water

AbstractParts‐per‐billion levels of cadmium and lead were detected using square‐wave anodic stripping voltammetry with a boron‐doped diamond electrode. Calibration plots (10‐minute deposition time) in KCl and KNO3 were non‐linear at low concentrations (1–5 ppb) due to the deposition mechanism of these metals. The preferred electrolyte for cadmium was KCl, while lead could be measured in either electrolyte. The lowest concentrations included in the linear portion of the calibration plot (5 minute deposition time) for cadmium were 10 ppb and 50 ppb in KCl and KNO3, respectively, and 10 ppb for lead in KNO3. The presence of either lead or copper suppressed the cadmium stripping peak, but the lead stripping peak was unaffected by cadmium, and enhanced by the addition of copper. A river water sample was analyzed for cadmium and lead, and the cadmium results were confirmed using ICP‐AES spectrometry. It was determined electrochemically that a fraction of lead in the river sample was bound by complexing material in the sample.

Stripping of Cadmium(II) Xanthato Complexes from the Anionic Surfactant Phase of Sodium Dodecylsulfate Gel to the Aqueous Phase

Stripping of Cadmium(II) Xanthato Complexes from the Anionic Surfactant Phase of Sodium Dodecylsulfate Gel to the Aqueous Phase

Determination of mercury in biological fluids by potentiometric stripping analysis.

A method is described for the determination of mercury by potentiometric stripping analysis. The analyte, Hg(2+), is employed for oxidizing a fixed amount of cadmium, previously reduced and amalgamated at a thin mercury film preplated on a glassy carbon electrode. The cadmium stripping signal correlates well with the amount of Hg(2+) added. Correlation coefficients of 0.9971 and 0.9960 were obtained for the two working ranges: (25 ng-2.5 microg) and (5.0-50) microg Hg(2+), respectively, in spiked water samples. The method was investigated with respect to precision and accuracy by spiking a natural water sample with 25 microg Hg(2+).Nine replicate determinations gave a mean value of 24.8 microg with a standard deviation +/-0.31 microg. The 95% confidence limit of the mean suggested the absence of systematic errors. Using the highest possible sensitivity, detection limits of 2.0 ng (167 ng/l) and 0.5 ng (4.2 ng/100 ml of whole blood) were obtained in water and blood samples, respectively. The applicability of the method was successfully extended to include the more complex matrices after recording a zero blank from authentic samples spiked with Cd(2+) (25 microg).The described PSA procedure is a simple and rapid method compared with the cold-vapor technique, with a 5.2% and 4.9% RSD, respectively.

Constant-current enhanced potentiometric stripping analysis

Constant-current enhanced potentiometric stripping analysis (CCEPSA) is similar to potentiometric stripping analysis (PSA) except that during the stripping step in CCEPSA a cathodic current is imposed on the electrode system. The freshly oxidized metal ions in the vicinity of the electrode surface are partially redeposited so that the stripping time is extended. The stripping time and potential-time equations for CCEPSA were derived and verified using the stripping of cadmium(II). Under the most favorable conditions, the sensitivity of cadmium(II) determination was enhanced by a factor of 15.

Mercury-coated carbon fiber microelectrodes : Preparation and some properties

Carbon fibre microelectrodes were made by sealing the fibres into glass and by using heat-shrinkable tubing. The electrodes can be coated with mercury by deposition at −0.9 V vs. SCE from 0.1 M thiocyanate containing 0.05 mM mercury(II) at pH 2.5. Coulometric measurements and square-wave voltammetry were used to establish the properties of the deposit. Conditions for the deposition and stripping of cadmium are outlined.

The effects of CopperZinc and CopperCadmium intermetallic compounds in different systems used for anodic stripping voltammetry

The CuZn intermetallic compound resulting from simultaneous deposition of copper and zinc at a hanging mercury drop electrode (HMDE) and at preformed mercury film electrodes (MFE) has been studied. Goals were to determine what conditions can be used to avoid intermetallic compound formation and to reduce errors that result from the method of standard additions. For Cu 2+ and Zn 2+ concentrations in the ng ml −1 range, the use of shortened preconcentration times in conjunction with a differential pulse stripping waveform and the HMDE show significant reduction in the extent of the interference. The CuCd interference was also characterized at performed MFE's and at MFE's deposited in situ from 5–300 μg ml −1 mercury(II) solutions. No significant interference with the cadmium stripping were was observed with preformed MFE's, but peak depression was observed when the electrodes were deposited in situ. The degree of interference was found to decrease with both increased mercury(II) concentrationa and decreased copper(II) concentration. Errors in the standard addition method are minimal when the copper(II) concentration is not significantly altered.