Copper Cadmium Research Articles

Recovery of cadmium from hydrometallurgical zinc smelter by selective leaching

A hydrometallurgical process for the recovery of cadmium was developed through a simple flowsheet of selective cadmium leaching from the Cd–Cu–Zn cake generated in electrolytic zinc circuit. The conventional route of cadmium leaching, sponging and re-leaching involves large number of stages and high capital expenditures. This research work relates to development of a simpler process approach for the recovery of cadmium in an electrolytic zinc circuit from the copper–cadmium cake of zinc purification section. The process consists of stages like zinc removal from copper–cadmium cake, selective cadmium leaching, and purification by removal of iron, thallium and cobalt followed by electrowinning and melting. The paper deals with zinc removal from copper–cadmium cake in two stages into the liquid phase with subsequent enrichment of copper and cadmium in cake. This cake was processed by selective cadmium leaching where a high solid–liquid ratio was maintained to attain higher cadmium concentration in the solution. The selective leaching of cadmium was performed under specific operating conditions so as to minimize co-dissolution of impurities into the cadmium rich solution. The reaction was terminated with start of copper dissolution. KMnO 4 and NaOH were used to oxidize and precipitate the impurities like Tl, Fe and part of Co. Purified cadmium sulphate solution was fed for electrolysis and the cadmium cathode so obtained was melted to achieve cadmium metal quality of 99.95%. The overall cadmium recovery of this process flowsheet was found to be 70–72%. Based on the research work, a conceptual flowsheet was developed.

Speciation of heavy metals in water from the Uganda side of Lake Victoria

Different forms of copper Cu, zinc Zn, lead Pb and cadmium Cd in water from the Uganda side of Lake Victoria (25°C, pH 6.75–7.18), the second largest inland freshwater lake in the world, have been studied using ion‐exchange, dialysis and atomic absorption spectrophotometry. The results indicate that heavy metals Cu, Zn, Pb and Cd are present mainly in the cationic form (80–83%). Small quantities of anionic (13–22%), non‐ionic, dialyzable (4–8%), and non‐ionic, non‐dialyzable (< 1.3–4.4%) forms were also detected for all metals except Cd. The corresponding concentrations lay in the ranges: cationic, 0.06–0.99; anionic, < 0.001–0.25; non‐ionic, dialyzable, < 0.001–0.08; non‐ionic, non‐dialyzable, < 0.001–0.06 µg ml−1. The existence of the metals in non‐ionic and non‐dialyzable forms is attributable to metal associations with high relative molecular mass (RMM) organic matters.

Quantification of 15N-Nitrate in Urine with Gas Chromatography Combustion Isotope Ratio Mass Spectrometry to Estimate Endogenous NO Production

The use of stable isotope labeled substrates and subsequent analysis of urinary nitrate, forms a noninvasive test for evaluation of the in vivo NO metabolism. The present paper describes a new method for simultaneous quantification of (15)N-nitrate and total nitrate with gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS). Nitrate, isolated from urine with a nitrate selective resin, was reduced to nitrite using copperized cadmium. Subsequently, Sudan I was formed by diazotation. Sudan II was added as internal standard, and both molecules were analyzed with GC-C-IRMS as tert-butyldimethylsilyl derivatives. The accuracy was determined during a recovery study of two different known nitrate concentrations and two (15)N-enrichments. A recovery of 101.6% and 103.9% for total nitrate and 107.6% and 91.2% for (15)N-nitrate was obtained, respectively. The validated method was applied on complete 72 h urine collections after intravenous administration of (15)N-nitrate and (15)N-arginine in humans. On average, 51.8% (47.0-71.0%) of administered (15)N-nitrate was excreted, while 0.68% (0.44-1.17%) of (15)N-arginine was metabolized to nitrate. In conclusion, this method can be used for accurate simultaneous determination of (15)N-nitrate and total nitrate concentrations in urine and can be applied in clinical studies for noninvasive evaluation of NO metabolism in vivo.

Determination of cadmium copper, iron, nickel, lead and zinc in crawfish [Procambrus clarkii] by inductively coupled plasma optical emission spectrometry: a study over the 2009 season in Southwest Louisiana

Following a mini-review of crawfish aquaculture, the concentrations (mean in micrograms of analyte per gram of dried sample ± 95% confidence interval, range) determined by inductively coupled plasma-optical emission spectrometry of cadmium (0.49 ± 0.14, 0.34–0.79 ), copper (34.9 ± 5.3, 23.8–44.2), nickel (1.83 ± 0.54, 1.08–3.39), lead (18.0 ± 4.0, 9.9–23.), iron, and zinc (47.3 ± 4.6, 41.3–55.8) were relatively constant with a slight increase in iron (620.4 ± 205.8, 328.8–1072.8) in whole crawfish in a season of 4 months (February through May 2009) in Southwest Louisiana. The temperature of the crawfish ponds was monitored weekly but had no effect on the metal concentration in the crawfish trial. The copper and zinc concentrations in the crawfish pond soil decreased with increasing temperature. The other four metals showing no effect of temperature variations (increase). A comparison with a previous study showed no significant changes in the metal concentrations in the crawfish.

CdCu3(OH)6(NO3)2: An S = 1/2 Kagomé Antiferromagnet

The cadmium copper hydroxide nitrate, CdCu(3)(OH)(6)(NO(3))(2).0.5H(2)O, is furnished from oxygenated suspensions of Cu(2)O in aqueous Cd(NO(3))(2). The compound possesses the kagome structural motif and shows no evidence of magnetic ordering to temperatures as low as 5 K, despite exhibiting a Curie-Weiss temperature of Theta = -114 +/- 27 K, thus giving a spin frustration parameter, f = 22.8.

Understanding and eliminating iron interference in colorimetric nitrate and nitrite analysis

Across many environments, nitrate (NO_3(-)) is an important form of N available for microorganisms and photosynthetic organisms. Accurate NO_3(-) measurements are important for examining N cycling and retention in terrestrial and aquatic ecosystems, but a common method of NO_3(-)) analysis can underestimate NO_3(-)) concentrations when soluble iron is present (iron > 10 mg L(-1)). The basic method is robust, using copperized cadmium to reduce NO_3(-)) and then diazotizing the resulting NO_2(-)) in a two-step process to form an easily measured colored product. We show that iron interference is unique to using an NH(4)Cl and ethylenediaminetetraacetic acid (EDTA) buffer. We hypothesize that interference is through iron-catalyzed reduction of the intermediate color product, a diazonium ion. We examine three historical buffers as alternatives to NH(4)Cl/EDTA and recommend replacement of EDTA with diethylenetriaminepentaacetic acid, which chelates metals much like EDTA, but unlike EDTA, it does not cause interference in the presence of iron.

New diagnostic tool to assess thin-film solar-cell reliability

Few subjects trigger as much passion as alternative or, more specifically, ‘green’ energy. Economical use of sunlight has been a key goal of scientists, engineers, and governments for over 50 years, given that the sun provides us hourly with enough energy to meet the annual electricity requirements of the entire world population.1 Solar cells (or photovoltaics: PVs) convert sunlight directly into electricity. Until recently, most PVs were based on single-crystal silicon. Yet, lack of grid parity (which refers to equal cost compared with existing, grid-based electricity sources) has discouraged their use. Recently, the PV industry has shifted towards adopting more exotic, thin-film materials, driven by the high sunlight-to-electricity conversion efficiencies attainable for cadmium telluride2 (CdTe) and copper indium gallium selenide—Cu(In,Ga)Se2—cells. Grid parity for thin-film modules (a packaged set of series-connected cells) is now almost certain.4 However, questions persist about their long-term reliability and, ultimately, the true cost of electricity: the longer a PV module functions, the cheaper it is. To achieve lower costs, materials like CdTe and Cu(In,Ga)Se2 are deposited quickly, often using low growth (or fabrication) temperatures. These conditions result in polycrystalline structures with sizes and thicknesses on the order of microns, which (although packaged using technologically advanced materials) are inherently more sensitive to long-term, outdoor exposure (10–20 years) than their monocrystalline counterparts. We employ a design-of-experiment approach combined with accelerated lifetime testing (ALT) to correlate the type of cellfabrication process with performance and reliability.5 ALTs enable us to estimate the long-term robustness of solar cells within a short period of time. Most current ALTs apply heat to accelerate degradation and measure changes in either the module’s power or the cell’s current-density/voltage (J–V) output characteristics to quantify reliability. Figure 1. Arrhenius plot for calculating degradation-activation energies in cadmium telluride (CdTe) solar cells. Time to fail was set arbitrarily as the time in which cells lose 10% of their initial performance, which is a function of temperature, T. Ea: Diffusion-activation energy.

Cadmium‐ and copper‐induced DNA damage in Pisum sativum roots and leaves as determined by the Comet assay

Alkaline single‐cell gel electrophoresis (Comet assay) enables sensitive detection of DNA damage in eukaryotic cells induced by genotoxic agents. The present work aims to study the genotoxic effects of cadmium or copper in pea (Pisum sativum L.) roots and leaves. We performed the Comet assay on cells exposed to cadmium chloride (0.35 mg kg−1, 0.7 mg kg−1, 1.4 mg kg−1, 7.0 mg kg−1) or copper chloride (35 mg kg−1, 70 mg kg−1, 140 mg kg−1, 700 mg kg−1) for 30 days. The tail moment in migrated DNA was regarded as an indication of DNA damage. The genotoxic test revealed a pronounced DNA alteration in roots of plants exposed to cadmium, and less in those exposed to copper. However, DNA damage in leaves was only significant in plants treated with the higher cadmium concentrations. Analysis of cadmium accumulation showed that roots accumulated almost 50‐fold more cadmium than above‐ground parts of the plant. This may explain the low genotoxic effects observed in leaves of cadmium‐treated plants.

Studies on the dynamics and mechanism of absorbing copper and lead and cadmium ions by Chlorella vulgaris

Studies on the dynamics and mechanism of absorbing copper and lead and cadmium ions by Chlorella vulgaris

Heavy Metal Mobility in Polluted Soils: Effect of Different Treatments

The effects of biosolid compost and phytoremediation applied on the leaching of cadmium, copper, lead and zinc, through the different horizons of a superficially polluted soil were determined. The soil was from the Province of Buenos Aires, Argentina. It was contaminated with cadmium copper, lead and zinc. Leaching columns were used with three different horizons: A: 0.12 m A horizon, B: 0.12 m horizon A+0.15 Bt horizon and C: 0.12 m A horizon+0.15 m Bt horizon+0.13 m BC horizon. The treatments were (1). Witness (contaminated soil), (2). contaminated soil+plants (Plant), (3). contaminated soil+50 Mg has-1 biosolid compost (Compost) and (4). contaminated soil+50 Mg has-1 biosolid compost+plants (Compost-Plant). The leached ones were gathered after incorporating to the columns the following volumes of water A: 1000 mL, B: 1200 mL and C: 2000 mL. Leachates were obtained out after harvesting vegetal material. It was found that horizon Bt presents a barrier to metal leaching. Both concentration of clay and type of clay appears to immobilize heavy metals in those soils. The clay content over 40% and/or 53.4 g smectite g-1 soils reduce the heavy metal leaching. The application of organic amendment or occurrence of plant eventually used in remediation techniques did not influence on the leaching of metals.

Hydride Generation-Atomic Fluorescence Spectrometric Determination of Cadmium in Pure Copper

An anion exchange-sequential injection hydride generation atomic fluorescence spectrometric procedure was specifically developed for the determination of ultra-trace cadmium in pure copper forbidden by the Restriction of the use of hazardous substances in electrical and electronic equipment (RoHS). A 50 mg l −1 copper concentration was employed in the standard solutions to match the copper matrix in the samples. In the presence of an appropriate amount of hydrochloric acid, the copper matrix was effectively eliminated by selectively absorbing the CdCl 4 2– complex onto a 717 anion exchanger packed mini-column. The present procedure could be used for the determination of cadmium in pure copper with a Cu/Cd mass ratio within the range of 2000–50000. A detection limit of 0.2 μg l −1 was achieved within a linear range of 1.0–25.0 μ g l −1, along with a RSD value of 3.0% (at 3.0 μ g l −1). The procedure was applied for the determination of cadmium in a pure copper sample, and spiking recoveries were also performed.

Contrasting Effects of Heavy Metals on Sponge Cell Behavior

Mediterranean coastal areas are highly contaminated by heavy metals, which have been reported to produce harmful effects in marine organisms. Sponges are particularly vulnerable to waterborne metals because they are able to process large amounts of water. Dissociated sponge cells can move in response to external stimuli, and the cell body changes shape through production of pseudopodia and phylopodia. We studied for first time the effects of heavy metals (cadmium copper and mercury) on motility and aggregation of isolated sponge cells. Cell shape was assessed by using several shape indices. The three metals studied induced changes of different sign on cell shape. Mercury arrested movement of sponge cells, which tended to be rounded, without pseudopodia. In contrast, moderate concentrations of copper and cadmium enhanced pseudopodia formation and cell motility. On the other hand, the three metals enhanced cell aggregation at the concentrations assayed. Our results show that sponge cells respond to metal pollution in different ways and that these responses can be assessed by calculating several shape indices.

TG-MS characterization of the reaction products of cadmium yellow and malachite artist’s pigments

The deleterious interaction of some traditional sulphide artists pigments and copper ions results in the formation of black copper sulphides, in particular, covellite (CuS), and, hence, the discolouration of valuable artworks. In this paper the interaction of malachite, a source of copper(II) ions, with the pigment cadmium yellow, a sulphide pigment comprising of a solid solution of cadmium and zinc sulphides, is investigated by XRD and TG-MS. XRD showed the presence of the copper sulphide and cadmium carbonate phases, produced by a simple ion exchange mechanism. TG-MS showed the complexity of the range of metastable phases produced. The identification of these phases, however, requires further work.

New Heterometallic Organosiloxanes

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Predicting toxicity in marine sediment in Taranto Gulf (Ionian Sea, Southern Italy) using Sediment Quality Guidelines and a battery bioassay

The goal of this study was to assess coastal marine pollution in the Mar Piccolo and Taranto Gulf (Ionian Sea, Southern Italy) by combining chemical and toxicological data in order to compare and integrate both approaches. Pollutants levels, traditionally, have limited ability to predict adverse effects on living resources. Moreover, in order to provide information on the ecological impact of sediment contamination on aquatic biota Numerical Sediment Quality Guidelines (SQGs) and sediment toxicity bioassays were carefully recommended. In this study ERL (effect range low)/ERM (effect range medium value) and TEL (threshold effect level)/PEL (probable effect level) guidelines have been used. Bioassays were performed with two species of amphipods Gammarus aequicauda and Corophium insidiosum, one species of isopod Idotea baltica and bivalve Mytilus galloprovincialis larvae. The TEL/PEL analysis suggested that, especially for stations 1 and 2, sediments in Mar Piccolo should contain acutely toxic concentrations of metals. In particular Hg content, in station 1, was about 17 times PEL value. 96 h LC(50) and 48 h EC(50) values were estimated for cadmium, copper and mercury in these species using the static acute toxicity test. M. galloprovincialis larvae was more sensitive than other species to all the reference toxicants tested (EC(50) determined for cadmium copper and mercury were of 0.59, 0.11 and 0.01 mg/l respectively). Significant differences in sensitivity of species tested to all reference toxicants (ANOVA p < 0.001) were recorded. Bioassays with these species allowed to estimated sediment toxicity from the different studied sites. On the basis of results obtained a good agreement was reported between chemical data and response of the biological endpoints tested.

ELECTROCHEMICAL EVALUATION OF THE POLYMER MODIFIED MICRO-ELECTRODE FOR METAL IONS

A porous micro-electrode with immobilized poly(methacryroyl alanine) (PMA) was developed for measuring copper(II) ion ( Cu 2+) and cadmium(II) ion ( Cd 2+). A porous carbon material was packed into the tip of the platinum micro-electrode with a cavity at the top. The porous micro-electrode was dipped in the coating dimethyl sulfoxide solution with PMA and di-2-ethylhexyl phthalate and dried overnight at room temperature. The immobilized PMA on the porous micro-electrode had predominantly a keto form in the buffer solution. In the enol form a metal complex can be formed under the simultaneous liberation of a proton. Calibration curves for measurements of Cu 2+ and Cd 2+, the effects of preconcentration condition, scan rate, pH, and temperature, and lifetime of the PMA modified micro-electrode were examined. Under optimal conditions, the responses of sensor were linear in the concentration range 0.0001~1 mmol 1-1 for Cu 2+ and 0.01~1 mmol 1-1 for Cd 2+. Analytical values determined with the modified electrode were constant for at least 3 month.

New heterometallic organosiloxanes

Among a diversity of bimetallic1 organometallo siloxanes (OMSO), compounds simultaneously contain ing transition and main group metals remained unknown. Combinations of transition and alkaline earth metals are of particular interest because alkali and alkaline earth metals are similar in electronegativity. Hence, the char acteristics of the structure formation of OMSO would be expected to be similar for such compounds. In addition, it is worthwhile to compare the influence of alkaline earth and other main group metals in the OMSO structure. We synthesized bimetallic OMSO, viz., calcium cop per phenylsiloxane (1) and cadmium copper phenyl siloxane (2), according to a procedure described earlier.2 This procedure involves the alkaline hydrolysis of phenyl triethoxysilane followed by the exchange reaction of the resulting organosilanolate and polyvalent metal halides. X ray diffraction study of OMSO 1 and 2 demon strated that these compounds are structurally similar and can be described as hexagonal prisms, whose upper and lower bases are formed by the six membered organo siloxane rings linked to each other by the metal oxide fragments O—M—O (Fig. 1). In all sandwich type bimetallic OMSO synthesized earlier, the prismatic cage has a cylindrical shape. By contrast, the cage in complexes 1 and 2 has an ellipsoid shape, the ellipsoid being elongated along the line be tween two main group metals, which is due to the fact that the ionic radii of the Ca and Cd atoms (1.00 and 0.87 A, the coordination numbers are 5 and 6, respec tively)3 substantially differ from that of the Cu atom (0.65 A, the coordination number is 5).3 The deviation from the cylindrical shape can be estimated from the dis tance between the opposite copper atoms. In μ6 (hexa phenylcyclohexasiloxanolato)hexacopper(II), which has been synthesized earlier,4 the corresponding distance is 5.5—5.7 A. In complex 2, this distance is substantially shorter (4.462(1) A). The replacement of the Cd atom by Ca leads to a further decrease in this distance (to 4.004(1) A), and the latter is comparable to the analogous distance (3.958(1) A) in the "globular" Cu,Na OMSO complex.5 Therefore, the partial replacement of Cu atoms by atoms with larger ionic radii leads to a distortion of the cylindrical shape of the cage, the degree of distortion being more likely determined by the ionic radius rather than by the nature of the introduced metal atom.

Trace metals in bulk freefall and roof intercepted rainwater at Ile-Ife, Southwest Nigeria

Samples of bulk freefall and roof-intercepted rainwater collected over five roof types (viz: Iron–Zinc sheets, Aluminum sheets, Asbestos sheets, Slate tiles, and Thatch) at Ile-Ife (SW Nigeria) were analysed for nine trace metals (aluminum, cadmium, chromium, copper, iron, lead, manganese, nickel, and zinc) using atomic absorption spectrophotometry (AAS). The mass concentrations and percent detection of the trace metals were generally higher in roof-intercepted samples than in the freefall samples. The ranking order of the mean concentrations of the metals in freefall samples (Al > Cr > Fe > Zn > Pb > Mn > Ni > Cu > Cd) is indicative of an atmospheric environment greatly influenced by heavy vehicular emissions and remobilized suspended particulate matter of soil origin. Mean metal enrichment of samples over the different roofs was in the order of Iron–Zinc > Aluminum > Thatch > Asbestos > Slate roof. Each roof sample type (except Slate samples) was characterized by relatively high enrichment of one or two metals. These include the high enrichment of zinc and iron in Iron–Zinc roof samples, cadmium and manganese in Aluminum roof samples, copper and manganese in Thatch roof samples and cadmium in Asbestos roof samples. The metal concentrations of roof-intercepted rainwater were lower than those of neighboring surface water, packaged table water, and vegetation-intercepted rainwater in the same environment. The metal levels in all the rainwater sources occurred within the allowable guide levels for most public and domestic applications.

Synthesis and characterization of mononuclear copper(II) and dinuclear cadmium(II) complexes with di-(2-picolyl)sulfide

The reaction of CuCl2 · 2H2O and CdCl2 with di-(2-picolyl)sulfide (dps) leads to the formation of mononuclear copper(II) and binuclear cadmium(II) complexes, [Cu(dps)Cl2] · H2O (1) and [(dps)(Cl)CdII(μ-Cl)2CdII(Cl)(dps)] (2). The copper atom in (1) is coordinated to one sulfur and two nitrogen atoms from the dps ligand and two chlorides in a distorted square-pyramidal environment. Complex (2) has two distorted octahedra sharing the basal edge that contain the bridging chloro ligands, each of which resides at a center of inversion. Cyclic voltammetric data show that (1) undergoes two reversible one-electron waves corresponding to CuII/CuIII and CuII/CuI processes. However, cyclic voltammetry of (2) gives two irreversible reduced waves.

Copper Adsorption with Pb and Cd in Sand-Bentonite Liners Under Various pHs. Part I. Effect on Total Adsorption

Municipal solid wastes could be segregated based on their specific heavy metal content and disposing of them in separate landfill cells. Therefore, the objective of the project was to investigate the interaction between copper (Cu) and either lead (Pb) or cadmium (Cd) using equilibrium batch adsorption experiments. A first test consisted of soaking three types of sand-bentonite liner samples (0, 5, and 10% bentonite) with a respective cation exchange capacities (CEC) of 2, 6.4, and 10.8 cmol(+)/kg in one of nine solutions consisting of a combination of three pH levels (3.7, 5.5, and 7.5) and three heavy metal solutions (Cu alone, Cu with Cd, Cu with Pb) each offering a respective heavy metal equivalence of 1, 2, and 2 cmol(+)/kg of liner. A second test set consisted in soaking 5% bentonite liner samples in three solutions at a pH of 3.7, with either Cu alone or with Pb or Cd, at 4.8 cmol(+)/kg of liner. For up to 14 days, duplicate samples were sacrificed to determine the supernatant Cu level and pH. The results indicated that under acidic conditions (pH< 6.5), the liner bentonite content, the solution pH and the presence of Pb or Cd significantly influenced Cu adsorption. Lead, and to a lesser extent Cd, competed with Cu for adsorption sites. Under alkaline conditions (pH> 6.5), carbonate and hydroxyl precipitation governed and masked the Pb and Cd competition. Thus, at low pH, limiting the presence of Pb in landfill leachate can improve Cu adsorption.