Deposition Of Cadmium Research Articles

Failure of 35NCD16 steel fastener – A metallurgical investigation

Cadmium plated 35NCD16 steel threaded fasteners are being used for aerospace applications. One such fastener, used in retainer assembly of holder interface of solid propellant motor case, parted into two pieces during its removal. The fastener was torqued to 10 Nm and was in assembly for a cumulative period of 45 days. The fracture surface of the failed fastener had a narrow central region consisted of dimples, while its surrounding region exhibited intergranular facets. From the evidence, it was concluded that the fastener failed due to hydrogen embrittlement. The possible sources for the hydrogen entrapment in the material were the furnace environment during heat treatment of the steel or inadequate baking of electroplated cadmium deposits. This paper highlights the details of metallurgical investigations carried out.

Peculiarities of the inhibiting effect of cadmium chloride on the corrosion of aluminum in hydrochloric solutions

The concentration effect of cadmium chloride on the corrosion rate of aluminum under conditions of the contact deposition of cadmium in hydrochloric acid solutions is studied. At changes in the contact deposition rate of the metal, in the surface area of the cadmium deposit, and the character of the deposits formed, the inhibiting effect of cadmium cations is shown to transform into the stimulating effect with an increase in the cadmium concentration in the solution. The reasons for the nonmonotonic character of the concentration dependence of the corrosion rate of aluminum are discussed.

Temporal trends (1990–2000) in the concentration of cadmium, lead and mercury in mosses across Europe

The European heavy metals in mosses survey provides data on the concentration of 10 heavy metals in naturally growing mosses. The survey has been repeated at five-yearly intervals and in this paper we report on the temporal trends in the concentration of cadmium, lead and mercury between 1990 and 2000. Metal- and country-specific temporal trends were observed. In general, the concentration of lead and cadmium in mosses decreased between 1990 and 2000; the decline was higher for lead than cadmium. For mercury not enough data were available to establish temporal trends between 1990 and 1995, but between 1995 and 2000 the mercury concentration in mosses did not change across Europe. The observed temporal trends for the concentrations in mosses were similar to the trends reported for the modelled total deposition of cadmium, lead and mercury in Europe.

Air quality and deposition of trace elements in Didouche Mourad, Algeria

Total suspended particulate matter and deposition fluxes of particles were investigated in the town of Didouche Mourad which is located 13 km north of Constantine. Samples of air particulate matter were collected at one site located in the heart of the town and situated 3 km north of a cement plant. Samples were collected from 2 November 2002 to 28 April 2003 every 3 days using a high volume air sampler. Sampling intervals were 24 h in all cases. During the same period, samples of dust fallout were collected at the same site. Samples were collected at 30-day intervals. Lead, chromium, manganese, nickel, copper, cobalt and cadmium deposition fluxes were measured and both the soluble and insoluble fractions were determined. Furthermore, the information gathered by this study was correlated with the corresponding hourly weather data provided by a weather station installed at the study station. The possible sources for dust and trace metals were analyzed by comparing average contributions of wind aspects to the concentrations and depositions of mass and chemical species with the average frequencies of wind direction. The mean concentration was 300 microg/m3. The average dust deposition rate through the period of study was 221 mg/(m2.day). Results indicate that anthropogenic sources contribute greatly to trace elements. An exposure assessment to the heavy metals taking into account the inhalation route and soil dust ingestion was carried out and allowed direct comparison of trace metal intakes via these routes.

Atmospheric deposition of cadmium in the northeastern USA

Lake sediment cores, dated by 210Pb, were collected from Spectacle Pond (SP), Massachusetts, and Side Pistol Lake (SPL) and Sargent Mountain Pond (SMP), Maine, USA. SP is a kettle seepage lake in granitic sand and gravel. SMP is a drainage pond on granite with little soil in the small watershed. SPL is a drainage lake in granitic till. The three cores were analyzed for total Cd. For SP and SMP, maximum concentrations of 1.7 and 3.9 mg/kg, four and eight times background concentrations, respectively, occur in the late 1960s. Accumulation rates reach maximum values concurrently with concentration and are 0.054 and 0.016 μg/cm 2/a, more than 10 times background. Concentration and accumulation rate age relationships in SMP and SP are similar for background values, timing and magnitude of increase to peak values, and the decrease nearly to background values since about 1975. The chemical response to decreased atmospheric deposition lags in SPL sediment. Kettle-like lakes more clearly indicate changes in atmospheric deposition than drainage lakes.

Underpotential Deposition of Thallium, Lead, and Cadmium at Silver Electrodes Modified with Self-Assembled Monolayers of (3-Mercaptopropyl)trimethoxysilane

Investigation of the underpotential deposition (UPD) of three metals-Tl, Pb, and Cd-on Ag surfaces modified with self-assembled monolayers (SAMs) of (3-mercaptopropyl)trimethoxysilane (3MPT) is reported. On the basis of the observation of negative potential shifts for their UPD processes, Tl and Pb undergo UPD directly on the underlying Ag surface by insertion between the Ag-S bond. This process is proposed to occur by penetration of the 3MPT monolayer by hydrated metal ions through spaces in six-membered siloxane rings that form at the terminus of the 3MPT layer after hydrolysis and condensation. In contrast, Cd does not undergo similarly facile UPD at 3MPT-modified Ag electrodes due to a hydrated ion size too large to fit through these openings. The voltammetric evidence that suggests that the hydrated metal cation size, as described by the Stokes diameter, is the primary determinant of Ag electrode accessibility for UPD through the cross-linked 3MPT layer is further supported by molecular mechanics energy minimization computations of six-membered siloxane rings on each of the three low-index faces of Ag. Finally, the 3MPT monolayer is shown to be exceptionally stable to repeated UPD/stripping cycles of Tl and Pb in contrast to SAMs of similar thickness formed from normal alkanethiols.

Atmospheric lead and cadmium deposition within forests in the Kanto district, Japan

Atmospheric lead and cadmium deposition in bulk precipitation and throughfall was investigated at four forests in the Kanto district, Japan, to assess the impact of human activities on the environmental health of forests. Annual lead and cadmium depositions in bulk precipitation ranged from 8.9 to 25.7 g ha−1 year−1 and from 0.77 to 1.30 g ha−1 year−1, respectively. Lead and cadmium deposition increased in the summer at every forest due to large amounts of rainfall. At one of the forests, the depositions were also high in the winter due to heavy snowfall. These depositions were similar to recent depositions observed at other rural and urban sites in Japan and several forests in Europe and North America after 1990. These results indicate that although anthropogenic lead and cadmium are deposited at these rates over wide areas, depositions are still higher than in remote areas.

Comment on “Role of the Anion in the Underpotential Deposition of Cadmium on a Rh(111) Electrode: Probed by Voltammetry and in Situ Scanning Tunneling Microscopy”

Comment on “Role of the Anion in the Underpotential Deposition of Cadmium on a Rh(111) Electrode: Probed by Voltammetry and in Situ Scanning Tunneling Microscopy”

Role of the Anion in the Underpotential Deposition of Cadmium on a Rh(111) Electrode: Probed by Voltammetry and in Situ Scanning Tunneling Microscopy

In situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV) were employed to examine the underpotential deposition (UPD) of cadmium on a rhodium(111) electrode in sulfuric and hydrochloric acids. The (bi)sulfate and chloride anions in the electrolytes played a main role in controlling the number and arrangement of Cd adatoms. Deposition of Cd along with hydrogen adsorption occurred near 0.1 V (vs reversible hydrogen electrode) in either 0.05 M H2SO4 or 0.1 M HCl containing 1 mM Cd(ClO4)2. These coupled processes resulted in an erroneous coverage of Cd adatoms. The process of Cd deposition shifted positively to 0.3 V and thus separated from that of hydrogen in 0.05 M H2SO4 containing 0.5 M Cd2+. The amount of charge (80 microC/cm2) for Cd deposition in 0.5 M Cd2+ implied a coverage of 0.17 for the Cd adatoms, which agreed with in situ STM results. Regardless of [Cd2+], in situ STM imaging revealed a highly ordered Rh(111)-(6 x 6)-6Cd + HSO4- or SO42- structure in sulfuric acid,. In hydrochloric acid, in situ STM discerned a (2 x 2)-Cd + Cl structure at potentials where Cd deposition commenced. STM atomic resolution showed roughly one-quarter of a monolayer of Cd adatoms were deposited, ca. 50% more than in sulfuric acid. Dynamic in situ STM imaging showed potential dependent, reversible transformations between the (6 x 6) Cd adlattices and (square root 3 x square root 7)-(bi)sulfate structure, and between (2 x 2) and (square root 7 x square root 7)R19.1 degrees -Cl structures. The fact that different Cd structures observed in H2SO4 and HCl entailed the involvement of anions in Cd deposition, i.e. (bi)sulfate and chloride anions were codeposited with Cd adatoms on Rh(111).

Transient conformation changes of albumin adsorbed on gold piezoelectrodes

The adsorption of bovine serum albumin (BSA) on Au piezoelectrodes was investigated using Electrochemical Quartz Crystal Nanobalance (EQCN), redox ion probe, and tapping-mode AFM techniques. The high ionic conductance of Au|BSA films, owing to the presence of voids, allowed for extensive studies of the templated deposition of cadmium and electrocatalytic nitrate reduction processes. Changes in BSA conformation in the adsorbed state were found to occur on completion of Cd-upd formation in the presence of nitrate ions. The conformational transition was reversible and BSA film integrity was preserved, as confirmed in multiple scan experiments and by carrying out Quartz Crystal Immittance (QCI) measurements. No change in the resonance admittance modulus versus frequency was observed. We have found that triggering of BSA conformational transition is not associated with bulk-Cd 0 nucleation and growth. Mechanistic considerations have led to the conclusion that BSA conformation changes are due to BSA adjustment to the changing electric field distribution in Au|BSA film associated with formation of surface complexes of partially charged Cd-upd with NO 2 − changing electrode charge and local pH increase caused by the electrocatalytic nitrate ion reduction. This mechanism is corroborated by the fact that in other Cd(II) solutions, not containing NO 2 − anions, conformational transitions in Au|BSA films were not observed.

STRONG LUMINESCING CdSe NANOPARTICLES BY SURFACE MODIFICATION WITH CADMIUM (II) HYDROUS OXIDE

CdSe nanoparticles were prepared by simply mixing Na 2 SSeO 3 solution with CdSO 4 solution under [ Cd 2+]/[ Se 2-] ( Cd/Se ) ratio of 1.2 at room temperature. The nanoparticles had an average size of 2.3 nm and showed fairly strong photoluminescence (PL) with a peak at 539 nm. Deposition of cadmium (II) hydrous oxide on the CdSe nanoparticles increased photoluminescence quantum yield from 3.1 to 34.8%, in comparison to Rhodamine 6G aqueous solution. Both of the CdSe nanoparticles and the cadmium (II) hydrous oxide deposited on CdSe nanoparticles were characterized as of cubic structure from XRD data and the electron diffraction (ED) patterns. Also, the reason for the photoluminescence enhancement was simply elucidated.

Comparison of Atmospheric Deposition of Copper, Nickel, Cobalt, Zinc, and Cadmium Recorded by Finnish Peat Cores with Monitoring Data and Emission Records

This study aims to determine the extent to which the accumulation rates of Cu, Ni, Co, Zn, and Cd in peat cores agree with established histories of atmospheric emission from local pointsources. Metals accumulating in three Finnish peat cores with known metal deposition histories have been measured using inductively coupled plasma-sector field mass spectrometry. Samples were age-dated using both 210Pb and 14C (bomb pulse curve). At the Outokumpu (OUT) site as well as the low-background site Hietajärvi (HIJ), 210Pb age dates are in excellent agreement with the 14C bomb pulse curve method results, and the precision is between 1 and 10 years for most of the samples; at the Harjavalta (HAR) site, precision is > 6 years. Mean regional "background" concentrations have been calculated from deeper peat layers of the HIJ site (microg g(-1)): Cu, 1.3 +/- 0.2 (n = 62); Co, 0.25 +/- 0.04 (n = 71); Cd, 0.08 +/- 0.01 (n = 23); and Zn, 4 +/- 2 (n = 40). For layers accumulated within the past 100 years, accumulation rates (ARs) have been calculated. At sites with < 0.06 g m(-2) cumulative Ni inventory (HIJ and OUT), ARs of Cu and Co trace the known metal deposition histories very well. At HAR, where metal inventories are much greater, Cu and Co are mobile. ARs of Zn were between 3 and 30 mg m(-2) year(-1) and those of Cd between 24 and 140 microg m(-2) year(-1) at all sites and are independent of the chronology of their inputs from the atmosphere.

Direct determination of cadmium in urine by electrothermal atomic absorption spectrometry after in situ electrodeposition

Determination of cadmium in urine by ETAAS suffers from severe interferences deteriorating the precision and accuracy of the analysis. Electrodeposition step prior to ETAAS allows to avoid interferences and makes cadmium determination possible even at ultratrace levels. The proposed procedures involve electrolytic deposition of cadmium from acidified urine on previously electrolytically deposited palladium film on a graphite atomizer tube, followed by removal of residual solution, pyrolysis and atomization. Both electrodeposition processes take place in a drop of the respective solution (palladium nitrate modifier and acidified urine, respectively), when Pt/Ir dosing capillary serves as an anode and the graphite tube represents a cathode. The voltage is held at −3.0 V. Matrix removal is then accomplished by withdrawal of the depleted sample solution from the tube (procedure A) or the same but followed by rinsing of the deposit with 0.2 mol l −1 HNO 3 (procedure B). The accuracy of both procedures was verified by recovery test. Detection limits 0.025 and 0.030 μg Cd/l of urine were achieved for A and B procedures, respectively. Both procedures are time consuming. The measurement cycle represents 5 and 7 min for A and B procedures, respectively.

Aerial deposition of cadmium before and after the closure of an oil-fired power station in the vicinity of two nursery roosts of Rhinolophus ferrumequinum (Chiroptera, Rhinolophidae)

Aerial deposition of cadmium has been monitored from 1994-1995 to the present by extraction of cadmium from petroleum jelly coated onto ceramic tiles placed near two nursery roosts and in the foraging area of greater horseshoe bats, Rhinolophus ferrumequinum. The mean cadmium deposit from aerial precipitation recorded in the area from 1994-1995 at locations which were upwind of the power station was 0.11 ± 0.05 mg/kg/mm rain per day compared with 1.01 ± 1.60 mg/kg/mm rain per day at locations downwind. After the oil-fired power station closed in 1996 subsequent analysis from 1998-2000 showed a slight increase in cadmium precipitation at upwind locations (0.22 ± 0.06 mg/kg/mm rain per day) but a decrease at the downwind locations (0.32 ± 0.07 mg/kg/mm rain per day). After closure of the oilfired power station near the bat roosts the aerial deposition of cadmium downwind was reduced but continued monitoring of the cadmium precipitation in the area is indicated since cadmium deposition still occurs. The deposits of cadmium have not had a major impact on the number of adult bats which have increased from 1994 to 2000. The findings made in this study have implications for conservation of the greater horseshoe bats which are at the Northern limit of their distribution.

Vegetable Crops for Biomonitoring Lead and Cadmium Deposition

Leafy vegetables are of particular interest for the active biomonitoring of the heavy metal deposition in the environment. The leaves accumulate the deposited airborne trace elements, however, they are also influenced by soilborne metals. The level of root uptake and accumulation depends on the element concerned and specific plant characteristics that influence the sensitivity of the biomonitoring system to a large extend. Standardization of the soil substrate and a precise estimation of the root uptake are very important in order to improve the sensitivity of biomonitoring. Spinach (Spinacea oleracea), lettuce (Lactuca sativa), endive (Cichorium endivia) and lamb’s lettuce (Valerianella locusta), grown in containers filled with a common peat soil and supplied with a semi-automatic watering system, were successfully used as bioaccumulators for the Cd and Pb deposition in gardens of an industrial and a residential area. Comparisons were made between the Cd and Pb contents in the crops and the deposition flux measured with NILU particulate fallout collectors in order to determine the accumulation efficiency of each crop. The correlations found were very useful to estimate the tolerable dust deposition levels with reference to the EU Guideline for maximum levels of contaminants in leafy vegetables. Exposure of the crops in open-top chambers, which were supplied with filtered air, (provided with a roof), proved that the Pb dust deposition significantly increases the “normal” concentration in the vegetables from the reference area, whereas the cadmium deposition was too low to be measured biologically. Comparisons of exposure of the crops to ambient air with or without chamber enclosure, and in open-top chambers with filtered air allowed to determine the “normal” metal concentrations and to estimate the “biological detection limits”.

Effect of surfactants on the cementation of cadmium.

The cementation of cadmium ions (Cd(2+)) from aqueous solution onto zinc was studied in two batch reactors, a batch stirred reactor lined with a cylindrical zinc sheet and another that used a rotating zinc cylinder. The rate of cadmium removal was studied as a function of speed of rotation, initial cadmium concentration, and the addition of certain surfactants and their mixtures. Rotational speed and initial cadmium concentration affect the rate of cadmium cementation. It was found that sodium dodecyl sulfate (SDS) improves the rate of cadmium cementation, while Triton X-100 and cetyltrimethylammonium bromide (CTAB) inhibit it. Thermodynamic parameters were calculated and discussed. Visual observations showed that cadmium deposits on the zinc sheet are in the form of a powder, while cadmium deposits on the zinc cylinder, in the presence of SDS, give porous grains which increases the roughness of the surface, leading to an increase in the cementation rate. The lowest deposit porosity was observed in the presence of CTAB, which corresponds to the highest decrease obtained in the rate of cadmium cementation. The cementation process was successfully applied to recover Cd(2+) spiked into an industrial wastewater sample.

New Facets of CdTe Electrodeposition in Acidic Solutions with Higher Tellurium Concentrations

Cathodic electrodeposition of cadmium telluride has been investigated in acidic aqueous solutions (pH 1-2) to explore the effect of the tellurium (IV) concentration at values higher than in classical conditions (typically a few This concentration was increased to The effects of the deposition potential and the hydrodynamic regime have been studied in a systematic way. The composition of the films, as well as their optical and structural properties, have been determined as a function of deposition parameters. The deposition of stoichiometric CdTe is obtained in a potential domain, positive with respect to the cadmium deposition potential, whose width decreases from about 0.5 V to a few millivolts when the current density increases, i.e., for higher growth rates (up to 10 μm per h). A composition-potential diagram has been established. The results are explained by analysis of a general deposition mechanism of CdTe, which enables for the first time an equation of the boundary lines of the stoichiometric domain. Outside this stoichiometric window, surprisingly, the variation of the composition is not continuous between CdTe and pure Te, but presents a large domain where the atomic ratio Cd/Te of the films is fixed at 0.5. This indicates the formation of a definite compound with an apparent composition which can be explained by extending Kröger’s theory to metastable compounds, as a result of an intermediate step in the deposition mechanism revealed by working under higher rates conditions. An optical bandgap of 1.3 eV and an amorphous structure are found for this compound. Upon thermal treatment, a phase separation takes place between Te clusters and the CdTe matrix. The formation of cadmium ditelluride, which has not been reported yet for other deposition methods, illustrates the interest of electrodeposition for obtaining low-temperature metastable phases. © 2004 The Electrochemical Society. All rights reserved.

Spectroelectrochemical sensing based on attenuated total internal reflectance stripping voltammetry. 3. Determination of cadmium and copper.

The optical and electrochemical properties of metallic films on ITO surfaces resulting from deposition of copper and cadmium were monitored by stripping voltammetry-attenuated internal reflectance spectroscopy. The voltammetric or optical responses of both metals were examined with respect to solution conditions such as pH and presence of dissolved oxygen. The morphologies of these films were also examined using environmental scanning electron microscopy, and the microscopic electrodeposition patterns were found to influence the optical response. The wavelength dependence of the optical response of deposited copper was determined and compared with calculations; optimal performance was at 400 nm for copper. A linear calibration curve was obtained over a range of 1 x 10(-7)-1 x 10(-4) M for copper and compared with that of cadmium. The simultaneous determination of cadmium and copper was demonstrated, and the mechanism of co-deposition is discussed.

Cadmium detection via boron-doped diamond electrodes: surfactant inhibited stripping voltammetry

The deposition of cadmium on boron-doped diamond is investigated with square-wave anodic stripping voltammetry. The system was investigated in quiescent conditions, in the presence of an acoustic field and then in the presence of the neutral surfactant Triton ® X-100. The effect of optimised insonation was to increase the sensitivity from 0.63 (under silent conditions) to 3.78 μA μM −1 and to reduce the limit of detection by an order of magnitude from 10 −8 to 10 −9 M. Measurements with or without insonation were found to deteriorate in the presence of the surfactant. Studies using AFM and chronoamperometry showed that this was due to inhibition of the deposition of the metal. Comparative data obtained for analogous measurements for copper on glassy carbon in the presence of industrial effluent, which also leads to signal deterioration under silent but not insonated conditions, showed that for this case also it was the nucleation of copper rather than the metal dissolution which was adversely affected.

The underpotential deposition of cadmium on Pt(1 1 1): effect of the anions and CO displacement experiments

The underpotential deposition (upd) of cadmium on Pt(111) electrodes in acidic solutions has been investigated. The formation of two upd layers prior to the onset of bulk deposition has been shown. Voltammetric and charge displacement experiments (as CO can displace Cd adatoms) allow an estimation of the Cd coverage corresponding to the upd layers. The first layer is relatively open (θcd≈0.31), probably because of important Cd–Cd repulsion, whereas the second is more compact. Charge displacement experiments also provide an estimate for the potential of zero charge of the Cd/Pt(111) electrode, which, as expected, lies between those of Pt(111) and Cd(0001) electrodes. Finally, the effect of chloride and bromide on the upd process has been studied. Both anions lead to an extraordinary sharpening of the voltammetric peaks, which results from the existence of strong attractive Cd–halide interactions at the electrode surface. In the case of bromide the main upd peak splits depending on cadmium and bromide analytical concentrations. This unusual behavior is thought to be caused by the separate adsorption of Cd2+ and CdBr+ species. The adsorption of CdBr+ would occur at more positive potentials probably induced by the presence on the electrode surface of preadsorbed bromide. The limitations of coulometry (either from voltammetry or from charge displacement experiments) for providing values of upd adatom coverage are discussed.