Binding Forms Of Heavy Metals Research Articles

The assessment of heavy metal binding forms in foundry wastes used as raw materials in agrotechnics, construction and road construction

The assessment of heavy metal binding forms in foundry wastes used as raw materials in agrotechnics, construction and road construction

Thermodynamic model of MSWI flue gas cooling path: Effect of flue gas composition on heavy metal binding forms.

In the context of circular economy and heavy metal (HM) recovery from municipal solid waste incineration (MSWI) fly ash (FA), detailed knowledge of HM binding forms is required for achieving higher extraction rates. The FA mineralogy is still poorly understood due to its low grain size and low metal concentration. To investigate the HM binding forms, a sophisticated thermodynamic reactive transport model was developed to simulate ash-forming processes. The stability of different binding forms was investigated at different flue gas conditions (varying ratios of HCl, SO2, O2) by simulating the gas cooling path in closed system and dynamic open system, where the gas composition is changing upon cooling due to precipitation of solids. The simulations predict that at flue gas conditions of molar ratio S/Cl < 1, Cu and Zn precipitate as oxides (and Zn silicates) at approximately 650°C. At temperatures <300°C, Zn, Cu, Pb and Cd are predicted to precipitate as easily soluble chlorides. In flue gas with molar ratio S/Cl > 1, the HM precipitate as less soluble sulphates. The results indicate that the less soluble HM fraction in the electrostatic precipitator ash represent oxides and silicates that formed in the boiler section but were transported to the electrostatic precipitator. The model provides insight into the physical-chemical processes controlling the metal accumulation in the flue gas and FA during the cooling of the flue gas. The obtained data serve as valuable basis for improving metal recovery from MSWI FA.

Effects of Surface Charge and Functional Groups on the Adsorption and Binding Forms of Cu and Cd on Roots of indica and japonica Rice Cultivars.

This work was designed to understand the mechanisms of adsorption of copper (Cu) and cadmium (Cd) on roots of indica and japonica varieties of rice. Six varieties each of indica and japonica rice were grown in hydroponics and the chemical properties of the root surface were analyzed, including surface charges and functional groups (-COO- groups) as measured by the streaming potential and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Binding forms of heavy metals adsorbed on rice roots were identified using sequential extraction methods. In rice roots exposed to Cu and Cd solutions, Cu existed mainly in both exchangeable and complexed forms, whereas Cd existed mainly in the exchangeable form. The amounts of exchangeable Cu and Cd and total adsorbed metal cations on the roots of indica varieties were significantly greater than those on the roots of japonica varieties, and the higher negative charges and the larger number of functional groups on the roots of indica varieties were responsible for their higher adsorption capacity and greater binding strength for Cu and Cd. Surface charge and functional groups on roots play an important role in the adsorption of Cu and Cd on the rice roots.

Inference model to predict heavy metals of Bahr El Baqar soils, Egypt using spectroscopy and chemometrics technique

With 35 soil samples gathered from the Bahr El Baqar region, Egypt, the objective of this study was to propose an inference model for prediction of heavy metals (Cd, Cu, Pb, Zn, Ni, Mn, Cr, Co, Fe) with visible near-infrared and short wave infrared (VNIR-SWIR) region (350–2500 nm). For a better understanding of the mechanism that allows the estimation of heavy metals with reflectance spectroscopy, statistical analysis was first made. The fingerprint region of 538, 578, 630, 870, 1900, 2240, and 2376 nm is very useful in recognizing small differences in the heavy metals of Bahr El Baqar region. Partial least squares regression (PLSR) is able to some extent (moderate accuracy) to model heavy metals with laboratory spectra parameters. The best coefficients of determination (R 2) between predicted and chemically analyzed concentrations were for Mn, 0.62; Pb, 0.66; Zn, 0.66, Ni, 0.69, and Cu, 0.60. Iron influences the soil reflectance in the VNIR-SWIR region. This is due to the electronic transition of iron cations (2+, 3+). Mn, Pb, Ni, Cu, and Zn were successfully predicted using PLSR. Only Cr (0.59) and Cd (0.52) content was predicted fairly. The analysis of correlation between heavy metal and soil constitutes of Fe2O3, Al2O3 and OM, which represented the clay minerals, iron oxides and organic matter, respectively, could support the above predicated binding forms of heavy metals. The order of the correlation coefficients from high to low between metal and wavelength is Cu > Zn > Mn > Co > Pb > Cr > Ni > Cd. This is almost the same as the order of their correlation coefficients with Fe2O3, Al2O3 and OM. These findings also validate a mechanism to predict heavy metals that have no absorption features in reflectance spectra. The results concerning the relationships between spectral parameters and heavy metals concentration indicate that iron oxides, clay, and OM play an important role in the prediction of soil heavy metals using reflectance spectra. To identify the specific wavelengths for prediction of the studied heavy metals, the regression coefficient with OM, Al2O3, and Fe2O3 were used. The most significant peaks for Zn prediction are found in the wavelengths of 430, 570, and 1700 nm; for Cu prediction at 538, 1259, 1500, and 2184 nm; for Pb significant peaks are at 440, 578, 915, and 1894 nm; for Cr at 860, 1001, and 2376 nm; for Ni at 870, 909, and 2240 nm; for Cd at 630, and 1270 nm; for Co at 1900, and 2300 nm. As the current results suggested, large concentrations of heavy metals can be predicted using reflectance spectroscopy. However, it is much more difficult to determine small concentrations of heavy metals in soils of Bahr El Baqar region. Organic matter masks spectral signatures, making it difficult to identify metal quantities at these wavelengths. So, a new concept “inference approach” in light of key soil constituents that absorb VNIR-SWIR radiation would became a powerful tool to enhance the accuracy of heavy metal prediction. Due to the interference effects of organic matter and low heavy metal concentration, the selection of the most sensitive original spectral bands still did not result in highly accurate prediction. Therefore, it is important to predict heavy metals through OM, iron oxides, or clays first. These results indicate that it is possible to predict heavy metals in soils using the rapid and economic reflectance spectroscopy.

Sediment Pollution, Transport, and Abatement Measures in the City Canals of Delft, the Netherlands

This paper presents an overview of a long-term study on sediment pollution in the city canals of Delft, the Netherlands. This pollution was most evident for the inner city canal system, with copper, lead, zinc, and polycyclic aromatic hydrocarbons (PAHs) as main pollutants. Sediments of the outer city canals generally had a much better quality. Pollution levels, mutual correlations, and spatial variations were investigated for the various sediment parameters. Also, heavy metal binding forms onto Delft sediments were assessed with the help of sequential extraction techniques; results were found to be in line with expected preferential physicochemical binding processes. Input of sediments into the Delft inner city canals was shown to be largely driven by busy shipping traffic on the main canal surrounding the inner city. Mass balances for the inner city were used to quantify internal and external pollution sources; 65–85 % of the heavy metal pollution can be attributed to sources outside the Delft area. As shown by factor and cluster analyses, it is highly probable that these external sources derive from the river Rhine. A gradual improvement of the sediment quality has set in; it is expected that, due to further pollution abatement measures, this improvement will continue over the years to come. With respect to the ship-induced sediment input into the inner city canals, it was estimated that a reduction of ship velocities to <1.5 m/s will bring down the sediment input mentioned above to about 85 %.

Plant Availability and Uptake of Lead, Zinc, and Cadmium in Soils Contaminated with Anti-corrosion Paint from Pylons in Comparison to Heavy Metal Contaminated Urban Soils

Red lead (Pb3O4) has been used extensively in the past as an anti-corrosion paint for the protection of steel constructions. Prominent examples being some of the 200,000 high-voltage pylons in Germany which have been treated with red lead anti-corrosion paints until about 1970. Through weathering and maintenance work, paint compounds and particles are deposited on the soils beneath these constructions. In the present study, six such “pylon soils” were investigated in order to characterize the plant availability and plant uptake of Pb, Cd, and Zn. For comparison, three urban soils with similar levels of heavy metal contamination were included. One phase extractions with 1 M NH4NO3, sequential extractions (seven steps), and extractions at different soil pH were used to evaluate the heavy metal binding forms in the soil and availability to plants. Greenhouse experiments were conducted to determine heavy metal uptake by Lolium multiflorum and Lactuca sativa var. crispa in untreated and limed red lead paint contaminated soils. Concentrations of Pb and Zn in the pylon soils were elevated with maximum values of 783 mg Pb kg−1 and 635 Zn mg kg−1 while the soil Cd content was similar to nearby reference soils. The pylon soils were characterized by exceptionally high proportions of NH4NO3-extractable Pb reaching up to 17% of total Pb. Even if the relatively low pH of the soils is considered (pH 4.3–4.9), this appears to be a specific feature of the red lead contamination since similarly contaminated urban soils have to be acidified to pH 2.5 to achieve a similarly high Pb extractability. The Pb content in L. multiflorum shoots reached maximum values of 73 mg kg−1 after a cultivation time of 4 weeks in pylon soil. Lime amendment reduced the plant uptake of Pb and Zn significantly by up to 91%. But L. sativa var. crispa cultivated on soils limed to neutral pH still contained critical Pb concentrations (up to 0.6 mg kg−1 fresh weight). Possible mechanisms for the exceptionally high plant availability of soil Pb derived from red lead paint are discussed.

Speciation Analysis of Heavy Metals of Core Amuta Sediments in Lianhua Lake

The BCR-SEP method was used to determine the binding forms of heavy metals in Amuta Lake(AMT) in this paper. The chemical forms of heavy metals, namely extractable fractions or valid fractions, including exchangeable-carbonate fraction, Fe-Mn oxide fraction and Organic-sulfide fraction .The results of the partitioning study indicated that in the core AMT sediments, Cr, Fe and Ni are mainly associated with the residue fraction, Cu is mainly concentrated in the Fe–Mn oxide fractions and residue fraction, Mn is concentrated in the exchangeable-carbonate fraction and residue fraction. Zn is concentrated in organic-sulfide fraction and residue fraction.

Content and Binding Forms of Heavy Metals, Aluminium and Phosphorus in Bog Iron Ores from Poland

Bog iron ores are widespread in Polish wetland soils used as meadows or pastures. They are suspected to contain high concentrations of heavy metals, which are precipitated together with Fe along a redox gradient. Therefore, soils with bog iron ore might be important sources for a heavy metal transfer from meadow plants into the food chain. However, this transfer depends on the different binding forms of heavy metals. The binding forms were quantified by sequential extraction analysis of heavy metals (Fe, Mn, Cr, Co, Ni, Cd, Pb) as well as Al and P on 13 representative samples of bog iron ores from central and southwestern Poland. Our results showed total contents of Cr, Co, Ni, Zn, Cd, and Pb not to exceed the natural values for sandy soils from Poland. Only the total Mn was slightly higher. The highest contents of all heavy metals have been obtained in iron oxide fractions V (occluded in noncrystalline and poorly crystalline Fe oxides) and VI (occluded in crystalline Fe oxides). The results show a distinct relationship between the content of Fe and the quantity of Zn and Pb as well P. Water soluble as well as plant available fractions were below the detection limit in most cases. From this we concluded bog iron ores not to be an actual, important source of heavy metals in the food chain. However, a remobilization of heavy metals might occur due to any reduction of iron oxides in bog iron ores, for example, by rising groundwater levels.

Fractionation behavior of heavy metals in soil during bioleaching with Acidithiobacillus thiooxidans

The effects of bioleaching on the fractionation of soil heavy metals were investigated in this study. Bioleaching of heavy metals from contaminated soil was carried out in shake flask experiments. Acidophilic sulfur oxidizing bacteria Acidithiobacillus thiooxidans isolated from soil was used for bioleaching. Bioleaching resulted in removal of heavy metals at higher levels. Variations in the binding forms of heavy metals before, during and after bioleaching were evaluated. It was noticed that bioleaching affected the binding forms of all the heavy metals present in the soil. The major contaminant chromium bound mainly to the fractions of soil which are not very reactive (organic and residual fractions) also showed good removal efficiency. Bioleaching influenced the fractionation of metals in soil after treatment and most of the remnant heavy metals were bound either to residual fraction or to other not easily mobile fractions of soil. The results of this study indicated that the bioleaching process can be useful for efficient removal of heavy metals from soil. Further, the soil with remnant metals can be disposed off safely.

Bioleaching of heavy metals from mine tailings by indigenous sulfur-oxidizing bacteria: Effects of substrate concentration

The aim of this study was to determine the effect of substrate concentration (elemental sulfur) on remobilization of heavy metals from mine tailings by indigenous sulfur-oxidizing bacteria. Also, the variation in the binding forms of heavy metals before and after bioleaching was explored. This work showed the laboratory results of bioleaching experiments on Pb–Zn–Cu mine tailings. The results showed that 97.54% Zn, 97.12% Cu, and 44.34% Pb could be removed from mine tailings by the bioleaching experiment after 13 days at 2% w/v substrate concentration. The results also indicated that substrate concentration 2% was found to be best to bacterial activity and metal solubilization of the five substrate concentration tested (0.5%, 1%, 2%, 3%, and 5%) under the chosen experimental conditions. The bioleaching had a significant impact on changes in partitioning of heavy metals.

Effect of redox potential on heavy metal binding forms in polluted canal sediments in Delft (The Netherlands)

Heavy metal binding forms for Cu, Zn and Pb were determined at four representative sediment sites in the canals of Delft (The Netherlands), using selective chemical extraction methods. Small differences (on average <5%) were found between duplicate extraction experiments. The dominant Cu binding form was always related to sulphide and organics in the sediment. Zn was mainly bound to iron+manganese (hydr)oxides, whereas Pb was rather evenly distributed over the different labile and non-labile binding fractions. A gradual (over about 1 month) increase in redox potentials of the anaerobic sediments led to a 7–37% sediment release of the above heavy metals; this could mainly be ascribed to oxidation of the heavy metal–sulphide bindings. Part of the released heavy metals was re-adsorbed by the labile binding phases (“exchangeable” and “carbonate bound”). Contrary to expectations, we found a decrease rather than an increase in the Fe+Mn (hydr)oxide binding forms. This can probably be ascribed to non-equilibrium reactions in the time span of the experiments, as well as side reactions such as complexation with humic acids and hindered precipitation reactions due to organic matter coatings.

In situ distributions and characteristics of heavy metals in full-scale landfill layers

The leachate from methanogenic landfill normally contains low concentrations of heavy metals. Little samples had ever been collected from the full-scale landfill piles owing to technical difficulty for well drilling. We drilled two wells in Hangzhou Tianziling landfill, 20 m and 32 m in depth each, and collected solid samples of waste age of 1–4 years from both wells. The total amounts, the sequentially extracted amounts, and the chemical binding forms of heavy metals of the samples collected at different depths were measured. With the correlation between leachate production amount and the yearly rainfall amount, the leached ratio of the heavy metals were estimated only 0.13%, 1.8%, 0.15%, and 0.19% of Cu, Cd, Pb, and Zn, respectively. The heavy metals amounts in the main compositions of MSW, like glass, food waste, paper, coal cinders, were measured using fresh MSW samples. Afterward, the contents of heavy metals initially landfilled were estimated. A positive correlation was noted between the measured and the estimated initial contents of heavy metals, indicating that the low migration of heavy metals in landfill layers. However, among the metals investigated, Zn has shown better mobility inside landfill layers. Acid volatile sulfide (AVS) and the simultaneously extracted metals (SEM) were measured for all collected samples with optimal reaction conditions identified to yield nearly perfect sulfide recovery as follows: 100 g wet samples, 80 mL min −1 N 2 flow rate, reaction time of 150 min. The SEM/AVS ratios ranged 25–45, indicating that the AVS was insufficient to immobilize the SEM. Sequential extraction using six-fraction scheme revealed that the sum of exchangeable and the avid soluble fractions of heavy metals follow: Zn > Cd > Cu, Ni, Pb > Cr. The insoluble fraction of heavy metals in MSW was high, for instance, over 80% for Cr and Pb high insoluble fractions of heavy metals in the landfilled MSW and the sorption capability of the methanogenic landfill layers should be responsible to the low concentrations of heavy metals found in leachate.

Electrokinetic enhancement removal of heavy metals from industrial wastewater sludge

An enhanced electrokinetic process for removal of metals (Cr, Cu, Fe, Ni, Pb, Zn) from an industrial wastewater sludge was performed. The electrokinetic experiments were conducted under a constant potential gradient (1.25 V cm −1) with processing fluids of tap water (TW), sodium dodecylsulfate (SDS) and citric acid (CA) for 5 days. Results showed that metal removal efficiency of heavy metals for EK-TW, EK-SDS and EK-CA systems are 11.2–60.0%, 37.2–76.5%, and 43.4–78.0%, respectively. A highest metal removal performance was found in EK-CA system. The removal priority of investigated metals from sludge by EK process was found as: Cu > Pb > Ni > Fe > Zn > Cr. The results of sequential extraction analysis revealed that the binding forms of heavy metals with sludge after electrokinetic process were highly depend upon the processing fluid operated. It was found that the binding forms of metals with sludge were changed from the more difficult extraction type (residual and sulfate fractions) to easier extraction types (exchangeable, sorbed, and organic fraction) after treatment by electrokinetic process. Results imply that if a proper treatment technology is followed by this EK process to remove metals more effectively, this treated sludge will be more beneficial for sludge utilization afterwards. Before it was reused, the risk associated with metals of more mobile forms to the environment need to be further investigated. The cost analysis was also evaluated for the investigated electrokinetic systems.

Distribution, removal and chemical forms of heavy metals in polluted rice seed

In this paper, the distribution, removal and binding forms of heavy metals in polluted seeds of rice were studied using the methods of histochemistry and biochemistry. The results indicate that the distribution of heavy metals in rice grains was very uneven. The heavy metals in rice grains chiefly exist in association with the parts of high protein. Separation of proteins by Sephadex chromatography and subsequent analysis by atomic absorption spectroscopy revealed that Cd, Pb and As were mainly bound to protein of 54.5 and 5.50 kD molecular weights. During the rice processing, the concentrations of heavy metals in the edible rice decrease greatly, for some heavy metals in these parts of chaff, coarse rice bran and fine rice bran were removed.

Spatial distribution of heavy metals in bottom sediment of Yenshui river, Taiwan

Distribution of heavy metals in bottom sediments from heavily polluted section of Yenshui river, located in the southern Taiwan, are presented. Sediment cores of seven sites were separated into several cuts and analyzed with both sequential extraction procedure (SEP) to realize the heavy metal contents (including Cr, Co, Zn, Ni, Pb, Cu and Cd) among binding fractions of different sediment depth and multivariate analysis (MA) to conduct the correlations of heavy metal variation in depth profile. Results show that distribution of heavy metals in depth profile of sediment is not identical among different sites. Levels of Zn, Cr, Cu and Ni were higher than other metals, and within the ranges of 30–200 mg/Kg, 8–160 mg/Kg, 5–130 mg/Kg, 10–100 mg/Kg, respectively. The major binding forms of Zn, Cr and Cu in sediment were ‘bound to carbonates’, ‘bound to Fe oxides’ and ‘bound to organic matter’ respectively. And, the percentages of different heavy metal binding forms were not significantly varied in depth profile. Results of principal component analyses (PCA) demonstrate that Cr, Ni and Cu were clustered, which indicate these metals had similar loadings in sediment profile, and might be discharged from the same pollution source of electroplating industry.

Spatial distribution of heavy metals in bottom sediment of Yenshui River, Taiwan

Distribution of heavy metals in bottom sediments from heavily polluted section of Yenshui river, located in the southern Taiwan, are presented. Sediment cores of seven sites were separated into several cuts and analyzed with both sequential extraction procedure (SEP) to realize the heavy metal contents (including Cr, Co, Zn, Ni, Pb, Cu and Cd) among binding fractions of different sediment depth and multivariate analysis (MA) to conduct the correlations of heavy metal variation in depth profile. Results show that distribution of heavy metals in depth profile of sediment is not identical among different sites. Levels of Zn, Cr, Cu and Ni were higher than other metals, and within the ranges of 30–200 mg/Kg, 8–160 mg/Kg, 5–130 mg/Kg, 10–100 mg/Kg, respectively. The major binding forms of Zn, Cr and Cu in sediment were ‘bound to carbonates’, ‘bound to Fe oxides’ and ‘bound to organic matter’ respectively. And, the percentages of different heavy metal binding forms were not significantly varied in depth profile. Results of principal component analyses (PCA) demonstrate that Cr, Ni and Cu were clustered, which indicate these metals had similar loadings in sediment profile, and might be discharged from the same pollution source of electroplating industry.

Effects of meliorative additives on the adsorption and binding forms of heavy metals in a contaminated topsoil from a former sewage farm

AbstractIn a laboratory study, a heavy metal contaminated topsoil from a former sewage farm in Berlin was amended with different additives: lime, ash/gypsum, bark mulch, brown coal and combinations of these treatments. After 8 weeks of incubation, pH of the lime and ash/gypsum treatments increased to 6.2–6.3 compared to 5.2–5.3 in the control and the other treatments. Organic‐C content rose from 42 g/kg in the control to 46–53 g/kg in the organic amendments. In reaction to the pH‐increase the water soluble fraction of Cd, Cu and Zn was reduced by roughly 60%, 30% and 80% respectively. Cd‐ and Zn‐binding forms as determined with NH4‐acetate‐ and EDTA‐extracts were not affected by the treatments, while the ash/gypsum‐treatment increased EDTA‐extractable Pb by 17%. The exchangeable Cu‐Fraction (NH4‐acetate extract) was reduced in all treatments to 82–93% of the control values, with the greatest effects in the tree bark amendment. The FREUNDLICH adsorption isotherms also show an increased sorption of heavy metals in the lime and ash/gypsum treatments. Organic amendments alone or in combination with lime had little effect on heavy metal adsorption.

Chemometric investigations on the differentiated evaluation of element trace analysis in river waters

The combination of sequential leaching methods for a first assessment of the kind of species in river sediments with multivariate-statistical methods (like factor analysis) for identifying anthropogenic and/or geogenic loading is useful for the differentiated characterization of the pollution state of a river. Electrochemical investigations, planned on the basis of statistical design and following empirical modelling, enables quantitative conclusions on the binding forms of heavy metals in river waters. Deposition-remobilisation effects of heavy metals in the complex system river water-river sediment can be described by PLS modelling.

Binding and Mobilization of Heavy Metals in Contaminated Sediments Affected by pH and Redox Potential

In a contaminated sediment from Hamburg harbour, acid production, mobilization of Cu, Zn, Pb, and Cd at different redox- and pH-conditions, and the transfer and change of those particle bound metals are studied. During oxidation the pH value in the sediment suspension decreases from about 7 to 3.4 because of the low acid neutralization capacity (ANC). This leads to a mobilization of heavy metals whereby Cd and Zn as distinguished from Cu and Pb are strongly released. Also a change in particulate phase specific heavy metal binding forms is found. Generally the easily and moderately reducible fractions increase during oxidation while the sulfidic fraction decreases. Also great changes were found for the dissolved Zn-and Cd-concentrations which increased continuously. The results show that at identical pH values obviously more metals are mobilized in the oxidized sediment than in the reduced state. But although the pH value is the key factor - in particular if it sinks below 4.5 - the redox conditions may also control the mobilization of certain metals. Consequently, also in well buffered sediments a mobilization of metals during oxidation cannot be excluded.

Binding and Mobilization of Heavy Metals in Contaminated Sediments Affected by pH and Redox Potential

In a contaminated sediment from Hamburg harbour, acid production, mobilization of Cu, Zn, Pb, and Cd at different redox- and pH-conditions, and the transfer and change of those particle bound metals are studied. During oxidation the pH value in the sediment suspension decreases from about 7 to 3.4 because of the low acid neutralization capacity (ANC). This leads to a mobilization of heavy metals whereby Cd and Zn as distinguished from Cu and Pb are strongly released. Also a change in particulate phase specific heavy metal binding forms is found. Generally the easily and moderately reducible fractions increase during oxidation while the sulfidic fraction decreases. Also great changes were found for the dissolved Zn-and Cd-concentrations which increased continuously. The results show that at identical pH values obviously more metals are mobilized in the oxidized sediment than in the reduced state. But although the pH value is the key factor - in particular if it sinks below 4.5 - the redox conditions may also control the mobilization of certain metals. Consequently, also in well buffered sediments a mobilization of metals during oxidation cannot be excluded.