Coprecipitation Of Copper Research Articles

Synthesis of Cu/SiO2(MCM-41) mesostructured catalysts. Effect of the preparation method on the textural properties and chemical structure

Two Cu/SiO2 mesoporous materials (Cu-MCM-41) were synthesized, one by the ion exchange (IE) post-synthesis method and the other, by the sol-gel (SG) method by co-precipitation of copper and silica (Cu-MCM-41) in the cetyltrimethylammonium bromide (CTAB) presence. The effects of the synthesis method on these materials were analyzed. They were characterized by XRD, N2 adsorption-desorption, TEM, DRUV–vis, FTIR, TPR, XPS, and FTIR with both, CO and pyridine adsorbed. Using the SG method, an MCM-41 material with a uniform mesoporous structure (Dp ≈ 35 Å), and a specific surface area (SBET) of 800 m2.g-1, was obtained. With the IE method and due to the partial collapse of the SiO2-MCM-41 mesoporous structure used as support, a material with a lower SBET (560 m2.g-1) was produced. The Cu in the SG synthesized material was mainly constituted by SiO-[CuO]n-CuOSi polymeric species and small CuO agglomerates. On the other hand, in the IE material, the copper was in the form of isolated SiO–Cu–OSi monomers, SiO–Cu–O–Cu–OSi dimers, and only a low proportion of SiO-[CuO]n-CuOSi oligomers. The catalytic activity of both materials was tested against the 2-propanol (2-PrOH) dehydrogenation in the gas phase. The reaction rate of the IE synthesized material was an order of magnitude higher than that prepared by the SG method. This behavior was attributed to the presence of SiO–Cu+ pair formed by the reduction of SiO–Cu–O–Cu–OSi dimmers present in the material prepared by IE; in contrast with the CuO aggregates obtained by the SG method.

A novel method for the recovery of silver from thiosulphate leach solutions using trimercapto-s-triazine (TMT)

• TMT effectively precipitates Ag from ammoniacal thiosulphate solutions. • Precipitation of Ag with TMT occurs fast. • TMT dosage is the most influential parameter on the recovery of silver. • Efficiency of the method is also demonstrated using real leach solutions. • A comprehensive characterisation of Ag-TMT precipitate is provided. In recent years, the demand for silver has increased due to its use in green technologies such as photovoltaic cells and electric vehicles (EVs). Due to environmental concerns associated with the use of cyanide leaching for gold/silver production, alternative lixiviants have received particular attention with thiosulphate having been often quoted as the most prominent one owing to its environmentally friendly characteristics and some technical advantages. However, thiosulphate leaching suffers from technical difficulties encountered particularly in the metal recovery from pregnant leach solutions. This study presents a novel approach for the recovery of silver from ammoniacal thiosulphate solutions through its precipitation using trimercapto- s -triazine (TMT), which is a non-toxic organo-sulphide reagent. Effects of concentration of TMT (0.07–0.33 mM), thiosulphate (0.20–1.00 M), and ammonia (0.40–1.00 M NH 3 ) on silver precipitation from synthetic Cu(II)–S 2 O 3 2− –NH 3 solutions were investigated by adopting the response surface methodology i.e., central composite design (CCD). The statistical analysis of the experimental data showed that the concentration of TMT had the highest impact on the extent of silver precipitation. Separate tests were also carried out to obtain the kinetic profiles of silver precipitation under varying concentrations of TMT (0.69–6.84 mM), copper (2.00–20.0 mM), and ammonia (0.10–1.00 NH 3 ) over 60 min. These results have also confirmed that silver can be readily and rapidly precipitated to the extent of 96.5% within a minute at a TMT concentration of 0.69 mM. The performance of the proposed method was also tested using real leach solutions derived from ammoniacal thiosulphate leaching of silver ore. It was found that extensive precipitation of silver (i.e., 99.0% Ag at 6.84 mM TMT) could be achieved with co-precipitation of copper (94.7%) and zinc (34.6%). SEM-EDS and FT-IR analyses were performed to characterise the precipitates obtained. This study has demonstrated that TMT can be used as a potent, non-toxic reagent for the recovery of silver from ammoniacal thiosulphate solutions.

Effect of Precipitated Precursor on the Catalytic Performance of Mesoporous Carbon Supported CuO-ZnO Catalysts

As part of concepts for chemical energy storage of excess chemical energy produced from renewable sources, we investigated the performance of CuO/ZnO catalysts supported on mesoporous carbon to convert CO2 hydrogenation to methanol. In this work, mesoporous carbon was used as the catalyst support for CuO-ZnO catalysts. Four catalysts with different precipitated precursors were synthesized and analyzed by N2-physisorption, X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that catalyst CZ-in situ had the highest turnover frequency (TOF) (2.8 × 10−3 s−1) and methanol production rate (0.8 mmol g−1·h−1). The catalysts for co-precipitation of copper and zinc on carbon precursors are more active. Cu/ZnO domains that are accessible to the reactant gas are another reason for the catalysts being active. The Cu-ZnO interface is crucial to methanol catalyst activity.

Water gas shift and sorption-enhanced water gas shift reactions using hydrothermally synthesized novel Cu–Mg–Al hydrotalcite-based catalysts for hydrogen production

As the interest in environmentally-friendly energy processes increases, many studies have been focused on producing hydrogen as an alternative energy carrier via catalytic reaction processes. Among several potential reaction processes, water gas shift (WGS) reaction has been studied extensively as a typical catalytic reaction for bulk production of hydrogen. Recently, many studies have been conducted on the formation of an easily reducible active components in order to develop novel catalysts having excellent activities at low temperatures for WGS reaction. In this study, new catalysts based on hydrotalcite with unique interlayered structure were prepared by a hydrothermal synthesis and co-precipitation of copper (Cu) for active metal sites. The catalysts synthesized from different precursors showed that the reduction property of Cu was greatly changed according to the mixed oxide structure generated after calcination. Cu–MgHAlH, the hydrotalcite-based catalyst synthesized using hydroxide precursors, showed the highest redox property and the multiple analysis results confirmed that MgAl2O4 spinel structure is attributed to form easily reducible Cu species. Based on these characteristics, Cu–MgHAlH showed excellent catalytic performance in the WGS reactions between 250 and 400 °C, and it was successfully applied to the sorption-enhanced WGS reaction using catalyst-sorbent hybrid solid pellets. Especially, the hydrotalcite-based catalyst has high potential for application to sorption-enhanced reaction processes using molten salt containing CO2 sorbents because the high reduction properties of Cu species are well maintained in the catalyst when mixed with CO2 sorbents.

Adsorption of Copper Ions by Microwave Treated Bentonite

Changes of bentonite surface structure under the influence of direct microwave irradiation during adsorpion of Cu2+ from concentrated solutions were investigated by X-ray and EDS analysis. The microwave treated bentonite (MTB) has been proved to have enhanced adsorption capacity for copper due to improved pore structure and some peculiarities of adsorption mechanism. The non-linear fitting of experimental data to the theoretical isotherms have demonstrated that the adsorption on natural bentonite fitted the Toth model, whilst microwave-treated bentonite fitted the Langmur-Freundlich model. The isotherm modeling allowed predicting the maximal adsorption capacities 44.8 mg/g. XRD and SEM analysis of MTB sample after adsorption indicated formation of microcrystals of individual copper compound. The adsorption on MTB sample takes place not only in pores or in monomolecular layer on the bentonite surface, but the prevalent mechanism is surface-induced co-precipitation of copper as microcrystals of individual copper compound.

Hydrogen trapping and desorption of dual precipitates in tempered low-carbon martensitic steel

The hydrogen trapping behaviors of dual nanometer-sized ε-copper and TiC carbide precipitates have been investigated in a low-carbon steel. The precipitation fashions were controlled by quenching and tempering at different austenization temperatures. The nanostructures of the dual precipitates were characterized by high-resolution transmission electron microscopy and atom probe tomography. Hydrogen desorption was studied through thermal desorption analysis of steels electrochemically charged with hydrogen. The hydrogen trapping capability of the precipitates was investigated through the release process. The precipitation routes of TiC carbides influenced the behavior of hydrogen trapping and the co-precipitation of copper and TiC carbides significantly increased the hydrogen trapping capability of the steels. These heat treatments can therefore be used to tailor the resistance to hydrogen embrittlement in tempered martensitic steels. Importantly, co-precipitated TiC and ε-copper particles in tempered martensitic steels show an enhanced capacity for hydrogen trapping and provide a range of trapping strengths. Co-precipitation is therefore proposed as a new prospect for designing steels with the capacity for substantial hydrogen trapping.

RESEARCH ON COPPER-67 SEPARATION OBTAINED BY PHOTO-NUCLEAR FROM ZINC OF NATURAL COMPOSITION

In the world, it is planned to produce promising for the manufacture of radiopharmaceuticals of radioisotope copper-67 by the reaction of its production from zinc-68 under the influence of γ-radiation on an electron accelerator. The next major issue is the separation of copper and zinc. Extraction, ion exchange and thermal distillation of zinc have already been studied in detail. Co-precipitation of copper with low zinc and thermal distillation of organic compounds of metals is promising.

Low pressure conversion of CO2 to methanol over Cu/Zn/Al catalysts. The effect of Mg, Ca and Sr as basic promoters

Carbon dioxide concentration level is reaching a non-returning point. Carbon capture technologies are immature and short-term actions are necessary. The conversion of CO2 into methanol is a technical challenge. Commercial copper-zinc-alumina catalysts convert maximum 7% carbon dioxide in syngas at high pressures (5 MPa to 10 MPa) and moderate temperatures (473 K to 573 K) into methanol. However, there are not records on the synthesis of methanol at low pressure (P<2.5MPa) and without a large excess of hydrogen in the feed. Here, we tested three new catalysts prepared by co-precipitation of copper, zinc and aluminum nitrates (CZA), with strontium, magnesium or calcium as basic promoters to enhance CO2 conversion to methanol. We discussed the microstructure of the catalysts according to the supersaturation of the relative carbonates formed during the co-precipitation synthesis. Compared to the benchmark, the sample doped with Ca showed higher carbon conversion with all the feed compositions tested (syngas, synthetic biosyngas and CO2 with H2). CZA doped with Sr is inactive in this reaction.

Developing a technology for processing cuprum containing wastes from galvanic production aimed at their further use

The study reports results of experimental studies into processing highly concentrated metal-containing wastes (HCMW) from galvanic production with obtaining precipitates of the predefined chemical composition, specified physical-and-chemical properties and with copper ions content. We defined the following precipitate properties in the study of copper-iron containing sludges obtained by coprecipitation of copper and iron-containing spent technological solutions (STS): humidity ‒ 89.7 %, density ‒ 1.17 kg/dm 3 , specific precipitate resistance ‒ 15–16∙10 11 m 2 /kg. It is easy to filter such precipitate. Therefore, it reduces consumption of reagents, increases purification efficiency, and makes it possible to obtain the precipitate, which is ready for transportation. Therefore, it is advisable to obtain copper-containing precipitates (sludges) with iron content for easier separation and avoiding of the conditioning operation. A technological scheme was developed for processing and subsequent disposal of copper-containing HCMW. It included transformation of copper- and iron-containing precipitate into a solution by addition of sulfuric acid; precipitation of iron ions with 25 % ammonia solution; separation of the obtained precipitate of iron hydroxide (ІІІ) by filtration for disposal; sending the obtained copper-containing filtrate for electrochemical removal of copper in the form of a metal precipitate or for disposal by the reagent method. We established in the processing of copper-containing HCMW in a diaphragm electrolyzer to extract copper in the form of a metal precipitate that the current consumption decreases with an increase in the initial metal concentration. Therefore, it is possible to ensure the degree of transformation of a=0.9 with current efficiency >80 % at the concentration of copper ions >0.1 mol/dm 3 . For reagent copper precipitation, it is optimal to use KOH and К 2 СО 3 mixtures рН=9.5–10 as reagents to obtain a hydroxocarbonate precipitate. Precipitates obtained in this way are suitable for further disposal by processing or they can be raw materials for production of ready-to-use products, which may be a final stage of galvanic production

Recovery of metals by ion exchange process using chelating resin and sodium dithionite

Chelating ion exchange resins can be used to recover metals from nickel laterite leach solution. The main problem is the high presence of iron. In pH above 2.00, iron precipitates and there is co-precipitation of copper and cobalt, which decreases recovery process efficiency. To solve this problem, a conversion of Fe(III) to Fe(II) can be the solution, where Fe(II) will precipitate just at pH 5.00. This reducing process can also increase metals recovery, where ferrous iron occupies less active sites on the resin than ferric iron. However, studies do not evaluate what happens to the resin under this situation. This work aimed to study the copper, nickel and cobalt recovery using chelating ion exchange resin Lewatit TP 207 and reducing process using sodium dithionite 1 mol.L−1. Sodium dithionite was used to convert Fe(III) to Fe(II). The effect of reducing agent on the resin was studied. Three different solutions where prepared to simulate the real nickel laterite leach solution. Batch experiments were performed to study the effect of pH to recover metals and to compare the results with and without the reducing agent. Results showed that metals adsorption increased when the ferric iron was converted to ferrous iron by reducing process. Chelating resin adsorbed more copper and also was selective for this metal at pH 2.50. Nickel and cobalt adsorption were higher at pH 3.50, but the resin was not selective for these metals under this pH. The order of selectivity of chelating resin changed when pH increased.

Pre-Reducing Process Kinetics to Recover Metals from Nickel Leach Waste Using Chelating Resins

The main problem of the separation process from nickel mining using the ion exchange technique is the presence of iron, which precipitates in pH above 2.00 and causes coprecipitation of copper and cobalt. Chelating resins have the main advantage of being selected for a specific metal present in solution. Studies have been developed to increase the efficiency of metals recovery using chemical reduction and the ion exchange process to recover metals. The aim of this work was to use sodium sulfite as a reducing agent to convert Fe(III) to Fe(II). Chelating resins Lewatit® TP 207, selective for copper, and Lewatit® TP 220, selective for nickel and cobalt, were studied. Batch experiments were performed to study the effect of pH with and without sodium sulfite. Results indicated that the industrial process has increased efficiency when the reducing process is applied.

Improving the packaging performance of low-density polyethylene with PCL/nanocellulose/copper(II)oxide barrier layer

A novel double layered hybrid materials, consisting of low density polyethylene (LDPE) base layer and polycaprolactone (PCL) top layer containing surface modified nanocellulose (NC) based nanocomposites in 0.5 and 2 % loadings, were studied in order to design multipurpose packaging material. NC was covalently modified with maleic anhydride (MA) to obtain NCMA, and upon co-precipitation of copper (II) oxide (CuO) on NC and NCMA surface, NC-CuO and NCMA-CuO nanocomposite materials were produced. Two drying methods, conventional and lyophilization, were applied to investigate process influences on the properties of obtained hybrid material. Oxygen transmission rate and antimicrobial activity were determined for all produced hybrid materials. PE-PCL-NCMA-CuO-L2 exhibited the highest antifungal properties, indicating contribution of MA residual group and drying conditions (liophylisation) to achievement of 97 % reduction in cell viability of C. albicans. The sample with 2 % of NCMA-CuO, PE-PCL-NCMA-CuO2, demonstrated to be the most promising material regarding improvement in antibacterial and antifugal activity, as well as 16 % lower value of the oxygen transmission rate in comparison to pure LDPE.

Direct synthesis of formic acid via CO2 hydrogenation over Cu/ZnO/Al2O3 catalyst

Cu/ZnO/Al2O3 catalysts were prepared by co-precipitation of copper, zinc, and aluminum nitrate hydrates (Cu: Zn: Al = 5:3:2, molar ratio) with 1 M NaHCO3 aqueous solution at several calcination temperatures (300, 400, and 500 °C) in air stream, and then reduced in H2-containing stream for 2 h. Crystal structures and particle morphologies of 300/400/500 °C-calcined Cu/ZnO/Al2O3 catalysts were thoroughly investigated. Shifts of pore textural properties and surface chemical compositions between fresh and used Cu/ZnO/Al2O3 were respectively observed using nitrogen isotherms and XPS spectra. Strengths of acidic and basic active sites over calcined Cu/ZnO/Al2O3 were measured with NH3 and CO2–TPD curves. Furthermore, the Cu/ZnO/Al2O3 calcined at 300 °C owned the largest dispersion of active copper (DCu = 53.90%) and maximum degree of reduction (Rmax = 60.8%), which is more favorable for HCOOH and CH3OH formations. Notably, the EXAFS spectra showed that the Cu species in catalysts have a CuO bonding with bond distances of 1.93–1.96 Å and coordination numbers of 2.25–2.47, respectively. It revealed that Cu atoms over Cu/ZnO/Al2O3 calcined at lower temperature have more unoccupied binding sites for HCOOH and CH3OH formations. In terms of catalytic performances, the highest CO2 conversion (13.1%), HCOOH selectivity (59.6%), HCOOH yield (7.6%), TON value (6.17), and TOF value (2.06) were gained at 140 °C and 30 bar in 5 h, respectively. The durability of Cu/ZnO/Al2O3 was 22 h in a 24-h measurement at 140 °C and 30 bar. The optimal rate constant (2.28 × 10−2 min−1) and activation energy (21.4 kJ mol−1) of HCOOH formation were respectively evaluated by pseudo first-order model and Arrhenius equation with good fitting. A mechanism was also proposed for HCOOH and CH3OH formations in the cyclic CO2 hydrogenation.

Preparation of high performance nano-sized Cu/ZnO/Al2O3 methanol synthesis catalyst via aluminum hydrous oxide sol

Ternary Cu/ZnO/Al2O3 methanol synthesis catalysts were synthesized by co-precipitation of copper and zinc hydroxycarbonates in the presence of various aluminum hydrous oxide sol preparation methods from sodium aluminate and aluminum nitrate as aluminum oxide sources. The catalysts were characterized at various stages of preparation by nitrogen adsorption-desorption, X-ray diffraction, transmission electron microscopy, temperature programmed reduction and N2O chemisorption techniques. The TPR profiles of calcined precipitates were deconvoluted into three peaks which were assigned to the reduction of copper oxide species exhibiting different crystallite size and/or different interactions with zinc oxide. All catalysts were tested for methanol synthesis activity in a fixed-bed reactor under conditions similar to that of commercial operation (503K, 50bar and GHSV of 17250h−1), using H2, CO, and CO2 (80/12/8 molar ratio) mixture as the feed. The experimental results illustrated that the catalyst synthesized based on aluminum hydrous oxide sol prepared by peptization of aluminum hydroxide exhibited higher specific surface area, copper dispersion and catalytic activity for methanol synthesis. The catalysts thus prepared were shown to have less hydrotalcite-like phase, stronger interdispersion between Cu and ZnO and well-dispersed Cu nanoparticles with improved stability and activity in methanol synthesis from syngas.

Influence of precipitation conditions on precursor particle size distribution and activity of Cu/ZnO methanol synthesis catalyst

Binary Cu/ZnO methanol synthesis catalysts were prepared by the co-precipitation of copper and zinc hydroxycarbonates using different initial solution concentrations, stirring rates and aging times and temperatures during precipitation, and different calcination temperatures of the precipitated hydroxycarbonates. The precipitates (catalyst precursors), fresh catalyst and were characterized at appropriate stages by nitrogen adsorption–desorption isotherm, X-ray diffraction (XRD), temperature programmed reduction (TPR), N2O chemisorption and particle size distributions measurement techniques. All catalysts were tested for methanol synthesis activity in fixed-bed reactor under conditions similar to that of commercial operation (503K, 50bar and GHSV of 17,250h−1), using of H2, CO, and CO2 (80/12/8mol ratio) mixture as the feed. During aging of the precursor, a sharp pH drop along with color change (from blue to green) was observed after certain aging time. Further, the particle size of precursors showed a decrease after color change. The time of this change was strongly dependent on the aging temperature and decreased by increasing aging temperature. At 40°C aging temperature, the catalyst activity increased with aging time but the resulting catalyst exhibited poor performance because the color change did not occur even after 65h of aging of the mother liquor. At 80°C aging temperature, a color change took place rapidly after about 0.5–0.75h of aging, and the catalyst activity increased with aging time followed by a decrease upon further aging. At a constant aging time of 5h, the catalyst activity increased with temperature in the range of 40–60°C and then decreased when temperature rose further from 60 to 80°C. The highest methanol synthesis activity (555gMeOH/kgcath) was observed for the catalyst prepared from 1M initial solution, 500rpm stirring rate and aged at 60°C. This was attributed to the small CuO crystallite size and large Cu surface area of the resulting catalyst.

Interaction of copper(II) and zinc(II) in coprecipitation from sulfate solutions with natural calcium carbonate

A coprecipitation of copper(II) and zinc(II) from complex sulfate solutions with natural calcite was investigated. The main features of the process and mineral forms of incorporation of heavy metals in a solid phase were determined. Sequential precipitation proceeds at pH 5.3–5.5 and 6.5–7.0 for copper(II) and zinc(II), respectively, in mode of pH autoregulation. Sediments were represented by copper and zinc hydroxosulfates: posnjakite and namuvite, respectively. Smithsonite and hydrozincite formation was not detected unlike precipitation of zinc(II) from monometallic sulfate solutions. The mechanism explaining the lack of zinc carbonates and the formation of mixed cation salts was suggested. The formation of hydroxosulfates should be considered in the thermodynamic description of the interaction of heavy metals with natural calcium carbonate.

Copper Ferrite (CuFe2O4) Nanoparticles

Ferrite (Fe3O4) nanoparticles (NPs) have been used as a catalyst for many organic transformations[1] because their nano-scale size equates to a large surface area to volume ratio (meaning many accessible active sites).[2] Moreover, iron-based magnetic properties enable easy catalyst recovery by the application of an external magnet. The catalytic scope of iron, however, pales in comparison with that of copper. Therefore, by substituting copper within the crystal lattice, the catalytic scope is greatly expanded, while the means of easy magnetic recovery are retained. The resulting copper ferrite nanoparticles (CuFe2O4 NPs) contain copper(II) and iron(III) species. Such nanoparticles can be obtained by co-precipitation of copper(II) and iron(III) salts (Scheme [1]).[3] They are also commercially available. Herein, the catalytic scope of CuFe2O4 NPs is highlighted and reviewed.

Protection of Metal Artifacts with the Formation of Metal–Oxalates Complexes by Beauveria bassiana

Several fungi present high tolerance to toxic metals and some are able to transform metals into metal–oxalate complexes. In this study, the ability of Beauveria bassiana to produce copper oxalates was evaluated. Growth performance was tested on various copper-containing media. B. bassiana proved highly resistant to copper, tolerating concentrations of up to 20 g L−1, and precipitating copper oxalates on all media tested. Chromatographic analyses showed that this species produced oxalic acid as sole metal chelator. The production of metal–oxalates can be used in the restoration and conservation of archeological and modern metal artifacts. The production of copper oxalates was confirmed directly using metallic pieces (both archeological and modern). The conversion of corrosion products into copper oxalates was demonstrated as well. In order to assess whether the capability of B. bassiana to produce metal–oxalates could be applied to other metals, iron and silver were tested as well. Iron appears to be directly sequestered in the wall of the fungal hyphae forming oxalates. However, the formation of a homogeneous layer on the object is not yet optimal. On silver, a co-precipitation of copper and silver oxalates occurred. As this greenish patina would not be acceptable on silver objects, silver reduction was explored as a tarnishing remediation. First experiments showed the transformation of silver nitrate into nanoparticles of elemental silver by an unknown extracellular mechanism. The production of copper oxalates is immediately applicable for the conservation of copper-based artifacts. For iron and silver this is not yet the case. However, the vast ability of B. bassiana to transform toxic metals using different immobilization mechanisms seems to offer considerable possibilities for industrial applications, such as the bioremediation of contaminated soils or the green synthesis of chemicals.

Preconcentration by Coprecipitation of Copper and Nickel with Mo(VI)/Triazole Derivative System and Their Determinations by Flame Atomic Absorption Spectrometry in Food and Water Samples

AbstractA new separation and preconcentration technique based on coprecipitation of Cu(II) and Ni(II) ions by the aid of Mo(VI)/di‐tert‐butyl{methylenebis[5‐(chlorobenzyl)‐4H‐1,2,4‐triazol‐3,4‐diyl]}biscarbamate (BUMECTAC) precipitate has been established. The Mo(VI)/BUMECTAC precipitate was dissolved by concentrated HNO3 and the solution was completed to 5.0 mL with distilled/deionized water. The levels of the analyte ions were determined by flame atomic absorption spectrometer. The effects of experimental conditions like HNO3 concentration, amount of BUMECTAC and Mo(VI), sample volume, etc. and also the influences of some foreign ions were investigated in detail on the quantitative recoveries of analyte ions. The preconcentration factors were found to be 40 for Cu(II) and 100 for Ni(II) ions. The detection limits for Cu(II) and Ni(II) ions based on 3σ (N:10) were 0.43 and 0.70 µg L−1, respectively. The relative standard deviations were found to be lower than 4.0% for both analyte ions. The accuracy of the method was checked by spiked/recovery tests and the analysis of two certified reference materials (Environment Canada TM‐25.3 and CRM‐SA‐C Sandy Soil C). The procedure was successfully applied to sea water and stream water as liquid samples and baby food as solid sample in order to determine the levels of Cu(II) and Ni(II) ions.

Mining-related contamination of surface water and sediments of the Kafue River drainage system in the Copperbelt district, Zambia: An example of a high neutralization capacity system

Contamination of the Kafue River network in the Copperbelt, northern Zambia, was investigated using sampling and analyses of solid phases and water, speciation modeling, and multivariate statistics. Total metal contents in stream sediments show that the Kafue River and especially its tributaries downstream from the main contamination sources are highly enriched with respect to Cu and exceed the Canadian limit for freshwater sediments. Results of sequential analyses of stream sediments revealed that the amounts of Cu, Co and Mn bound to extractable/carbonate, reducible (poorly crystalline Fe- and Mn oxides and hydroxides) and oxidizable (organic matter and sulfides) fractions are higher than in the residual ( Aqua Regia) fraction. Compared to Cu, Co and Mn, Fe is bound predominantly to the residual fraction. Values of pH in the Kafue River and its tributaries are alkaline in the contaminated area and concentrations of sulfate gradually increase downstream. Water balance based on sulfate indicates that inflow from the most contaminated tributaries is less than 5% of total discharge in the Kafue River. There is a significant input of Cu and Co from multiple contamination sources close to the town of Chingola, located on the Mushishima tributary, but both metals are mostly bound to suspended particles, which settle in the Kafue River. Additional contaminant sources such as the Uchi mine tailings and Nkana smelter are located in the industrial area around Kitwe, but metals released from these sources are mostly found in suspension and are attenuated efficiently. Low Fe/Cu ratios in suspension and mineralogical composition of stream sediments downstream of contaminant sources around Chingola indicate that native copper, Cu-sulfides, and Cu carbonates are present in stream sediments in addition to Cu bound to Fe(III) oxide and hydroxides. The Nkana smelter fingerprint in stream sediments is recognized by the presence of slag glass and a Cu-Fe-S intermediate solid solution (ISS). Speciation modeling suggests a possibility of precipitation of some Cu phases in the most contaminated tributaries such as the Mushishima. In the early dry period (mid-May) dissolved and suspended Cu and Co concentrations are lower than in the advanced dry period (late June). When the scale of mining and related activities in the Copperbelt is taken into account, the environmental impact of mining and related activities on the Kafue River is relatively limited due to a high neutralizing capacity of the mining wastes which control the rapid precipitation of iron oxides and hydroxides as well as adsorption and/or co-precipitation of copper, and cobalt. The high metal content in stream sediments, however, may pose a potential environmental risk during accidental acid spikes, when significant fractions of metals in sediments can be re-mobilized.