Binary Metal Mixtures Research Articles

Extraction of U(VI) with Cyanex 302

U(VI) was quantitatively extracted from 1·10−3M HNO3 using 5·10−3M Cyanex 302 in xylene and was stripped from organic phase with 5M HCl. The optimum extraction conditions have been evaluated by studying parameters like acidity, effect of diluents, extractant concentration and period of equilibration. Based on this data, the separations of uranium from binary and complex metal mixtures and its recovery from uranmicrolite tailings (leachate) were successfully tested. Uranium can be determined with a relative standard deviation of 0.4%.

Determination of types of interactions exhibited by binary mixtures of heavy metals tested against the hermit crab, Clibanarius africanus

Single and joint action toxicity of heavy metal compounds (ZnCO3, CuSO4 and CdSO4) were carried out against the hermit crab, Clibanarius africanus in laboratory bioassays. On the basis of 96 h LC50 values, CuSO4 (96 h LC50 = 0.03 mM) was found to be the most toxic followed by CdSO4 and ZnCO3 (96 h LC50 = 0.24 mM) in decreasing order of toxicity. The evaluation of the metal compounds in mixtures of ZnCO3–CuSO4, ZnCO3–CdSO4 and CdSO4–CuSO4 in pre-defined molar ratios revealed that interactions between Zn–Cu and Zn–Cd test mixtures were in conformity with the models of antagonism (reduction in toxicity of constituent metals). The synergistic ratios (S.R.s) and relationship between observed/predicted 96 h LC50 values (relative toxic unit, RTU) were consistently below 1, indicating antagonistic interactions. Analysis using isobolograms also indicated the interactions between the mixture components to be antagonistic. However, with regards to CdSO4–CuSO4 test mixtures, the interactions between these metals were mainly in conformity with the model of synergism. The S.R. and RTU values were largely above 1, indicating synergistic interactions. The importance of the joint action evaluations for the management and protection of aquatic ecosystems, particularly in the setting up of water quality criteria was discussed.

Toxicity of binary mixtures of metals and pyrethroid insecticides to Daphnia magna Straus. Implications for multi-substance risks assessment

Two different concepts, termed concentration addition (CA) and independent action (IA), describe general relationships between the effects of single substances and their corresponding mixtures allowing calculation of an expected mixture toxicity on the basis of known toxicities of the mixture components. Both concepts are limited to cases in which all substances in a mixture influence the same experimental endpoint, and are usually tested against a “fixed ratio design” where the mixture ratio is kept constant throughout the studies and the overall concentration of the mixture is systematically varied. With this design, interaction among toxic components across different mixture ratios and endpoints (i.e. lethal versus sublethal) is not assessed. In this study lethal and sublethal (feeding) responses of Daphnia magna individuals to single and binary combinations of similarly and dissimilarly acting chemicals including the metals (cadmium, copper) and the pyrethroid insecticides (λ -cyhalothrin and deltamethrin) were assayed using a composite experimental design to test for interactions among toxic components across mixture effect levels, mixture ratios, lethal and sublethal toxic effects. To account for inter-experiment response variability, in each binary mixture toxicity assay the toxicity of the individual mixture constituents was also assessed. Model adequacy was then evaluated comparing the slopes and elevations of predicted versus observed mixture toxicity curves with those estimated for the individual components. Model predictive abilities changed across endpoints. The IA concept was able to predict accurately mixture toxicities of dissimilarly acting chemicals for lethal responses, whereas the CA concept did so in three out of four pairings for feeding response, irrespective of the chemical mode of action. Interaction effects across mixture effect levels, evidenced by crossing slopes, were only observed for the binary mixture Cd and Cu for lethal effects. The analysis of regression residuals showed that interaction effects across mixture ratios were restricted to feeding responses in binary mixtures that included Cu. These results indicate that the ability of the CA and IA concept to predict mixture toxicity effects varies from lethal to sublethal endpoints irrespective of their primary mode of action. This suggests that when considering complex responses, the pharmacological notion of mode of action should be extended to encompass an ecotoxicological mode of action, based on the concentration at which various toxicological effects become operative in the biological system under consideration.

Binary biosorption of cadmium(II) and nickel(II) onto dried Chlorella vulgaris: Co-ion effect on mono-component isotherm parameters

The competitive biosorption of cadmium(II) and nickel(II) onto dried Chlorella vulgaris, a green alga from binary metal mixture was studied and compared with single metal ion situation in a batch stirred system. The effects of single- and dual-metal ion concentrations on the biosorption capacity of biomass were investigated at an initial pH value of 4.0. Equilibrium uptake of cadmium(II) and nickel(II)) increased with increasing its initial metal ion concentration up to 150 mg l −1 and decreased considerably by the presence of increasing concentrations of the other metal ion. Both the Freundlich and Langmuir adsorption models were suitable for describing the biosorption equilibrium of cadmium(II) and nickel(II) ions both in single and binary systems. According to the Langmuir model the maximum biosorption capacity of dried alga was determined as 86.6 mg g −1 for cadmium(II) and as 58.4 mg g −1 for nickel(II) for single ion situation. These values dropped to 68.5 mg g −1 for cadmium(II) and to 28.3 mg g −1 for nickel(II) when co-ion concentration was kept at 150 mg l −1. For each metal ion, variation of isotherm constants due to the level of other metal ion were expressed as a function of initial co-ion concentration by non-linear regression techniques.

Interactive toxicity of simple chemical mixtures of cadmium, mercury, methylmercury and trimethyltin: model-dependent responses

Scientific and societal interest in the analysis of aggregate toxicity derives from the fact that people are seldom exposed to single chemicals, but rather to multiple agents from different sources and even to mixtures of agents from a single source. Many descriptive terms and mathematical, graphical, and statistical models have been used to evaluate the toxicity of simple mixtures. It is not very easy to distinguish clearly the intrinsic differences, distinctions and limitations of these models when applied to characterizing interactive toxicity. A series of experiments were performed to illustrate model-dependent consistencies and differences in interactive toxicity. Cultured murine renal cortical cells, target cells for metal toxicity, were treated with selected concentrations of one metal or binary mixtures of metals to give conditions of dose-additivity, response additivity, or with only one toxic member of the binary mixture. The cytotoxicity was determined at 24 h by lactate dehydrogenase release. The data were analyzed graphically and mathematically by (a) Carter's statistical isobologram, (b) Barton's non-linear, and (c) Kodell and Pounds’ linear models to characterize the interaction. These models were compared and contrasted for robustness, and consistency using these common data sets. The models gave generally consistent conclusions, but each model has limitations and strengths for assessing particular mixtures scenarios. This comparison illustrates the complexity of extrapolating conclusions between models, and difficulty of public health assessment from exposures to multiple chemicals in the environment.

Improving the performance of carbon composites by liquid phase activated sintering of MCMBs doped with Ti/Ni or Fe/Ni

A novel fabrication method for carbon composites using liquid phase activated sintering at 1400 °C in vacuum is described. Specimens for testing were prepared by subjecting mixtures of mesocarbon microbeads (MCMBs), Ti/Ni or Fe/Ni powders, and suitable additives, to aqueous tape casting, and molding the tapes into laminates prior to sintering. After sintering XRD showed that there were some eutectic liquid phases formed in the composites, which were favorable to enhancing the densification and reducing the porosity of the carbon composites. The reduction of the interlayer spacing of graphite crystallites due to the addition of the binary metal particles showed that the formation of the eutectic liquid promoted graphitization. The results showed that both the bend strength and the electrical conductivity of the carbon composites were also improved with the addition of the binary metal mixture.

Toxic Properties of Metals and Organotin Compounds and Their Interactions on Daphnia magna and Vibrio fischeri

In the present study toxicity tests were performed in order to determine the toxic properties of four organotin compounds and three heavy metals and to examine the interactive effects of binary metal mixtures on two different test species: the freshwater crustacean Daphnia magna and the marine bacterium Vibrio fischeri.D. magna proved to be more sensitive to metals than V. fischeri. Tributyltin chloride and copper were found to be the most toxic substances on both test organisms. The interactive effects between trimethyltin chloride/copper and trimethyltin/chromium on both test species were investigated and synergistic, additive and antagonistic actions were observed.

Using factorial experiments to study the toxicity of metal mixtures

Two-level factorial experiments were employed in this study for understanding and predicting the toxicity of binary and ternary metal mixtures. Toxicity of metal mixtures with concentrations between the respective EC 10 and EC 80 values was experimentally measured. Models were fit to the experimental data and the resultant models were of high quality as reflected by R 2 (coefficient of determination). Interactions between mixture components were indicated by the existence of statistically significant interaction terms in the models. Toxicity predictions based on the models were compared with observed toxicity for binary and ternary metal mixtures. The models developed did not assume additivity between metals, were simple and interpretable, and gave satisfactory predictions of the toxicity of metal mixtures in aqueous solutions without requiring knowledge on synergism or antagonism.

Advances in Quantitative Ion Character‐Activity Relationships (QICARs): Using Metal‐Ligand Binding Characteristics to Predict Metal Toxicity

AbstractEnvironmental toxicologists readily adopted QSARs from pharmacology to predict organic contaminant toxicity. In contrast, models relating metal ion characteristics to their bioactivity remain poorly explored and underutilized. Quantitative Ion Character‐Activity Relationships (QICARs) have recently been developed to predict metal toxicity. The QICAR approach, based on metal‐ligand binding tendencies, has been applied successfully to a wide range of effects, species, and media on a single metal basis. In previous single metal studies, a softness parameter and the |log KOH| were among the ion qualities with the highest predictive value for toxicity.

Compositional effects on the mechanochemical synthesis of Fe–Ti and Cu–Ti amorphous alloys by mechanical alloying

It is well-known that the mechanochemical processing of binary mixtures of transition metals can induce the formation of nanostructured and amorphous phases. Previous kinetic studies have shown that the phase transformation in binary mixtures follows sigmoidal conversion curves irrespective of the intensity of mechanical processing. The rate of such transformations is instead strongly influenced by both the intensity of the mechanical treatment and the physical properties of the reactant powders. In the present work, we give additional information on the amorphisation kinetics of binary mixtures by exploring the effect of composition on the transformation kinetics. Cu–Ti and Fe–Ti mixtures with composition within the amorphisation ranges have been subjected to mechanical processing at fixed intensity. The kinetics of phase transformation has been followed by quantitative X-ray diffraction. The experimental data obtained demonstrate that the amorphisation rate has a strong dependence on the product of the mass fractions of the single reactants.

Multivariate curve resolution of overlapping voltammetric peaks: quantitative analysis of binary and quaternary metal mixtures.

The application of multivariate curve resolution-alternating least squares (MCR-ALS) to the quantitative analysis of different metal ion mixtures using voltammetric data is described. The performance of MCR-ALS was evaluated in the resolution and quantitation of overlapped voltammetric peaks obtained in the analysis of binary and quaternary mixtures of Cd(II), In(III), Pb(II) and Tl(I) metal ions by anodic stripping voltammetry. Quality assessment of qualitative and quantitative determinations was evaluated considering the effects of different constraints and of initial estimations. MCR-ALS results were validated and compared with those obtained by applying other well-established multivariate calibration methods, such as partial least squares (PLS) and direct classical least squares (DCLS) methods.

Removal of divalent heavy metal mixtures from water by Saccharomyces Cerevisiae using crossflow microfiltration

The removal of heavy metal ions, Ni 2+, Cu 2+ and Pb 2+ using yeast ( Saccharomyces cerevisiae) as carriers in a crossflow microfiltration is investigated. The effects of yeast cell and electrolyte concentrations on the transient and steady-state permeate flux and metal ion rejections are established. It is found that the metal ion rejection reaches a plateau if yeast cell concentration is greater than ∼2 g/l as a result of cell aggregation. The binding affinity of the metals to yeast cell is Pb 2+>Cu 2+>Ni 2+, which is also reflected in the metal ion rejection under identical process conditions. Because of the formation of yeast cell flocks in the presence of Pb 2+, permeate flux is also higher for this metal. The presence of NaCl decreases both rejection and permeate flux for Ni 2+ and Cu 2+ but not for Pb 2+. When binary or ternary metal mixtures are used, the rejection of the individual metals is reduced except that of Pb 2+. It is found that the pseudo-gel concentration is unaffected by the presence of metal ions.

Direct Quantification of Metal‐Organic Interactions by Size‐Exclusion Chromatography (SEC) and Inductively Coupled Plasma Mass Spectrometry (ICP‐MS)

AbstractMetal speciation significantly influences the geochemical cycling of trace metals and can control metal bioavailability and toxicity. Advanced analytical techniques have been applied to address some difficulties encountered in identifying metal organic species. In this method, size‐exclusion chromatography (SEC) was directly coupled with inductively coupled plasma mass spectrometry (ICP‐MS) to determine conditional stability constants of metal complexes with strong organic ligands in competitive equilibration experiments. Molecular size calibration of the column was performed with polystyrenesulfonate standards and the effects of hydrophobic interactions on the column were determined. Metal concentrations corresponding to different organic fractions were measured directly, in the SEC column effluent, by ICP‐MS. The method was validated with well‐defined organic ligands in ligand competition studies with a single metal and a binary metal mixture. The distribution of metal‐ligand species determined analytically was shown to correspond to the calculated equilibrium speciation. Model studies using metal complexes with weaker organic ligands demonstrated that the technique is subject to kinetic limitations since labile metal‐organic complexes can dissociate during chromatographic separation. Nonetheless, the kinetic window of the method should be appropriate for the strong ligands postulated to control metal speciation in natural waters.

Equilibrium parameters for the single- and multicomponent biosorption of Cr(VI) and Fe(III) ions on R. arrhizus in a packed column

In this study, simultaneous biosorption of Cr(VI) and Fe(III) on free Rhizopus arrhizus in a packed column operated in a continuous mode was investigated and compared to the single metal ion situation. The breakthrough curves were measured as a function of feed flow rate and different combinations of metal ion concentrations in the feed solutions. Column competitive biosorption data were evaluated in terms of the maximum (equilibrium) capacity of the column, the amount of metal loading on the R. arrhizus surface, the adsorption yield, and the total adsorption yield. Since the maximum column capacity and the adsorption yield decreased with increasing concentrations of the other metal ion, the combined action of Cr(VI) and Fe(III) on R. arrhizus was generally found to be antagonistic. In the single-ion situation, the adsorption isotherms were developed for optimum conditions and it was seen that the adsorption equilibrium data fit the non-competitive Freundlich model. For the multicomponent adsorption equilibrium, the competitive adsorption isotherms were also developed. The empirical Freundlich model for binary metal mixtures represented satisfactorily most of the column adsorption equilibrium data of Cr(VI) and Fe(III) on R. arrhizus.

Biosorption of Lead(II), Nickel(II), and Copper(II) on Rhizopus arrhizus from Binary and Ternary Metal Mixtures

The biosorption of three divalent metal ions [Pb(II), Ni(II), and Cu(II)] frequently encountered together in industrial waste waters and in binary and ternary systems was studied using Rhizopus arrhizus, a filamentous fungus, in batch stirred reactors. The multimetal biosorption data were evaluated in terms of equilibrium isotherms and adsorption yields. The single-metal equilibrium data were analyzed using the Freundlich adsorption model. The individual Freundlich adsorption constants were determined and used to compare biosorptive capacity of the microorganism for different metal ions. The effects of various combinations of the metal ions on the biosorption capacity of R. arrhizus are discussed and the actions of the synergistic or antagonistic metal ion combinations were determined. For the two-metal adsorption equilibrium, competitive adsorption isotherms have been also developed. The six-parameter empirical Freundlich model, restricted to bicomponent systems, was used successfully to characterize simultaneous biosorption of Pb(II), Ni(II), and Cu(II) ions by R. arrhizus from two-metal systems. The biosorption capacity of Pb(II) in the two binary and one ternary systems, in agreement with the single-metal data, was greater than that of the Ni(II) and Cu(II) ions. The relative capacities were Pb(II) > Ni(II) > Cu(II) at pH 5.0 in single, binary, and ternary systems.

Modelling of a single-staged bioseparation process for simultaneous removal of iron(III) and chromium(VI) by using Chlorella vulgaris

In this study, the competitive biosorption of iron(III) and chromium(VI) to Chlorella vulgaris from a binary metal mixture was investigated in a single-staged batch reactor as a function of V 0/ X 0 (volume of solution containing heavy metal mixture/quantity of biosorbent) ratio and second metal ion concentration at pH 2. The obtained results showed that the increase in biomass quantity (or the decrease of V 0/ X 0 ratio) with the addition of second metal ion affected the removed quantities of iron(III) or chromium(VI). The sorption phenomenon was expressed by the competitive, multi-component Langmuir adsorption isotherm and this expression was used for calculating each residual or adsorbed metal ion concentration at equilibrium ( C eq, i or C ad,eq, i ) at a constant V 0/ X 0 ratio for a given combination of heavy metal ions in a single-staged batch reactor. Experimental C eq, i and C ad,eq, i values were compared to those calculated and graphically determined.

Short-term ecotoxicity of a mixture of five metals to the zebra mussel Dreissena polymorpha.

Konemann (1981) observed that a mixture of a large number of organic toxicants with the same mode of action, had an additive effect on survival of fish. However, it has been suggested that the potential for addition may be reduced when sublethal instead of lethal parameters are studied (Hermens et al. 1984; Deneer et al. 1988). Furthermore, it is likely that inorganic toxicants, like metals, have different modes or sites of action. Consequently, metals may affect a specific biological endpoint differently. Therefore, it is likely to expect deviations from concentration addition when sublethal effects of a mixture of metals are determined. Indeed, studies on the effects of binary sublethal metal mixtures found such deviations from additivity, either less or more than concentration addition (Mohan et al. 1986; Van Gestel and Hensbergen 1997; Weltje, 1998). Kraak et al. (1994a), studying the effects of binary metal mixtures on the filtration rate of the zebra mussel (Dreissena polymorpha), also observed more as well as less than additive effects. However, a mixture of three metals (Cu, Zn and Cd) was concentration additive. Although this could be purely incidental, it could also be argued that the deviations from concentration addition were “averaged out” in a mixture consisting of more than two metals. Based on the latter assumption, it could be suggested that a mixture of several metals is not likely to deviate from additivity. However, when the number of compounds in a mixture increases, the concentration of the individual compounds decreases. This may imply that in such a mixture essential metals (Cu, Zn, Ni) do not, or to a lesser extent, contribute to the toxicity of the mixture, because low concentrations of essential metals are under metabolic control (Amiard

A single-staged bioseparation process for simultaneous removal of copper(II) and chromium(VI) by using C. vulgaris

The simultaneous biosorption of copper(II) and chromium(VI) to C. vulgaris from binary metal mixtures was investigated in a single-staged batch reactor as a function of V0/X0 ratio (volume of wastewater containing heavy metal mixture/quantity of biosorbent) at different orders of second metal ion addition and at pH values of 2.0 and 4.0 chosen as the optimum biosorption pH values for chromium(VI) and copper(II), respectively. The increase in biomass quantity (or the decrease of V0/X0 ratio) with the addition of the second metal ion affected the removed quantities of chromium(VI) and copper(II) due to pH. The sorption phenomenon was expressed by the competitive, multi-component Freundlich adsorption isotherm and this expression was used for calculating each residual or adsorbed metal ion concentration at equilibrium (Ceq,i or Cad,eq,i) at a constant V0/X0 ratio for a given combination of heavy metals in a single-staged batch reactor. Experimental Ceq,i values were compared to those calculated and graphically determined.

Combination toxicology of copper, zinc, and cadmium in binary mixtures: Concentration‐dependent antagonistic, nonadditive, and synergistic effects on root growth in Silene vulgaris

AbstractUsing Silene vulgaris (Moench) Garcke as a test plant, the combination toxicology of Cu, Cd, and Zn was studied. Plants were exposed to single metals and binary metal mixtures in a factorial design. Root elongation after 3 d of exposure was used as a toxicity endpoint. The responses to mixtures were classified using nonaddition, response addition, and, where possible, concentration addition as reference models. In all the metal combinations tested, the nature of the joint effect appeared to be strongly concentration‐dependent. The responses were approximately nonadditive (Cu/Zn, Cu/Cd) or antagonistic (Zn/Cd) with respect to root growth inhibition as long as the concentrations of both components of the mixture were kept within the slightly toxic range. As soon as one of the mixture components exceeded a critical level of toxicity, synergism was the predominant joint effect, even when the concentration of the other component was nontoxic under single‐metal exposure. Further increases of the metal concentrations eventually decreased the degree of synergism, possibly as a result of increasing antagonisms at the level of metal uptake. The strongly synergistic effects of root‐internal metals in the more concentrated mixtures seemed to be due to sensitizing secondary effects other than saturation of common cellular detoxification mechanisms.

Investigation of Simultaneous Biosorption of Copper(II) and Chromium(VI) on Dried Chlorella Vulgaris from Binary Metal Mixtures: Application of Multicomponent Adsorption Isotherms

Although the biosorption of single metal ions to various kinds of microorganisms has been extensively studied and the adsorption isotherms have been developed for only the single metal ion situation, very little attention has been given to the bioremoval and expression of adsorption isotherms of multimetal ions systems. In this study the simultaneous biosorption of copper(II) and chromium(VI) to Chlorella vulgaris from a binary metal mixture was studied and compared with the single metal ion situation in a batch stirred system. The effects of pH and single- and dual-metal ion concentrations on the equilibrium uptakes were investigated. In previous studies the optimum biosorption pH had been determined as 4.0 for copper(II) and as 2.0 for chromium(VI). Multimetal ion biosorption studies were performed at these two pH values. It was observed that the equilibrium uptakes of copper(II) or chromium(VI) ions were changed due to the biosorption pH and the presence of other metal ions. Adsorption isotherms were developed for both single- and dual-metal ion systems at these two pH values, and expressed by the mono- and multicomponent Langmuir and Freundlich adsorption models. Model parameters were estimated by nonlinear regression. It was seen that the adsorption equilibrium data fitted very well to the competitive Freundlich model in the concentration ranges studied.