Desorption Of Copper Research Articles

Copper Release, Speciation, and Toxicity Following Multiple Floodings of Copper Enriched Agriculture Soils: Implications in Everglades Restoration

This study characterizes the effects of water–soil flooding volume ratio and flooding time on copper (Cu) desorption and toxicity following multiple floodings of field-collected soils from agricultural sites acquired under the Comprehensive Everglades Restoration Plan (CERP) in south Florida. Soils from four field sites were flooded with three water–soil ratios (2, 4, and 6 [water] to 1 [soil]) and held for 14 days to characterize the effects of volume ratio and flooding duration on Cu desorption (volume ratio and flooding duration study). Desorption of Cu was also characterized by flooding soils four times from seven field sites with a volume ratio of 2 (water) to 1 (soil) (multiple flooding study). Acute toxicity tests were also conducted using overlying waters from the first flooding event to characterize the effects of Cu on the survival of fathead minnows (Pimephales promelas), cladocerans (Daphnia magna), amphipods (Hyalella azteca), midges (Chironomus tentans), duckweed (Lemna minor), and Florida apple snails (Pomacea paludosa). Acute tests were also conducted with D. magna exposed to overlying water from the second and third flooding events. Results indicate that dissolved Cu concentrations in overlying water increased with flooding duration and decreased with volume ratio. In the multiple flooding study, initial Cu concentrations in soils ranged from 5 to 223 mg/kg (dw) and were similar to Cu concentration after four flooding events, indicating retention of Cu in soils. Copper desorption was dependent on soil Cu content and soil characteristics. Total Cu concentration in overlying water (Cuw) was a function of dissolved organic carbon (DOC), alkalinity, and soil Cu concentration (Cus): log(Cuw) = 1.2909 + 0.0279 (DOC) + 0.0026 (Cus) − 0.0038 (alkalinity). The model was validated and highly predictive. Most of the desorbed Cu in the water column complexed with organic matter in the soils and accounted for 99% of the total dissolved Cu. Although total dissolved Cu concentrations in overlying water did not significantly decrease with number of flooding events, concentrations of free Cu2+ increased with the number of flooding events, due to a decrease in DOC concentrations. The fraction of bioavailable Cu species (Cu2+, CuOH+, CuCO3) was also less than 1% of the total Cu. Overlying water from the first flooding event was only acutely toxic to the Florida apple snail from one site. However, overlying water from the third flooding of six out of seven soils was acutely toxic to D. magna. The decrease in DOC concentrations and increase in bioavailable Cu2+ species may explain the changes in acute toxicity to D. magna. Results of this study reveal potential for high Cu bioavailability (Cu2+) and toxicity to aquatic biota overtime in inundated agricultural lands acquired under the CERP.

Copper desorption in flooded agricultural soils and toxicity to the Florida apple snail ( Pomacea paludosa): Implications in Everglades restoration

Copper (Cu) desorption and toxicity to the Florida apple snail were investigated from soils obtained from agricultural sites acquired under the Comprehensive Everglades Restoration Plan. Copper concentrations in 11 flooded soils ranged from 5 to 234 mg/kg on day 0 and from 6.2 to 204 mg/kg on day 28 (steady-state). The steady-state Cu concentration in overlying water ranged from 9.1 to 308.2 μg/L. In a 28-d growth study, high mortality in snails occurred within 9 to 16 d in two of three soil treatments tested. Growth of apple snails over 28 d was affected by Cu in these two treatments. Tissue Cu concentrations by day 14 were 12–23-fold higher in snails exposed to the three soil treatments compared to controls. The endangered Florida snail kite and its main food source, the Florida apple snail, may be at risk from Cu exposure in these managed agricultural soil–water ecosystems.

In situ removal of copper from sediments by a galvanic cell

This study dealt with in situ removal of copper from sediments through an electrokinetic (EK) process driven by a galvanic cell. Iron (Fe) and carbon (C) were placed separately and connected with a conductive wire. Polluted sediments were put between them and water was filled above the sediments. The galvanic cell was thus formed due to the different electrode potentials of Fe and C. The cell could remove the pollutants in the sediments by electromigration and/or electroosmosis. Results showed that a weak voltage less than 1 V was formed by the galvanic cell. The voltage decreased with the increase of time. A slight increase of sediment pH from the anode (Fe) to the cathode (C) was observed. The presence of supernatant water inhibited the variation of sediment pH because H + and OH − could diffuse into the water. The removal of copper was affected by the sediment pH and the distribution of electrolyte in sediment and supernatant water. Lower pH led to higher removal efficiency. More electrolyte in the sediment and/or less electrolyte in the supernatant water favored the removal of copper. The major removal mechanism was proposed on the basis of the desorption of copper from sediment to pore solution and the subsequent electromigration of copper from the anode to the cathode. The diffusion of copper from sediment to supernatant water was negligible.

Thermodynamics of copper desorption from soils as affected by citrate and succinate

Desorption of Cu and low molecular weight dissolved organics are the primary factors that impact fate and transport of Cu in soils. To improve predictions of the toxicity and threat from Cu contaminated soil, it is critical that time-dependent desorption behaviour be understood. In this paper, the effect of organic ligands citrate and succinate on the kinetics of Cu desorption from contaminated soils varying widely in soil characteristics was investigated at three different temperatures. The results showed that the first order equation adequately described the kinetics of Cu desorption from clay and sandy soils under isothermal conditions. The reaction rate constant (k<sub>d</sub>) values of the first order kinetic equation for Cu desorption increased consistently with temperature, indicating faster release of Cu at higher temperatures. The Cu desorption rate from the studied soils at all three temperatures was as follows: citric > succinic. The E<sub>a</sub>values indicates that Cu desorption from the studied soils in the presence of two organic ligands is a diffusion controlled reaction. The negative values of ΔH* suggest that the desorption reactions are not energy consuming process. The higher negative values of (ΔH*) for Cu desorption from the studied soils in the presence of succinic ligand indicate that the heat energy required to overcome the Cu desorption barrier was greater than that for Cu desorption in the presence of citric ligand. Computation of the free energy of activation (ΔG*) yielded values ranging for 87 to 87.9 kJ/mol. The largest value represents ΔG* for Cu desorption for clay soil in the presence of succinic acid while the lowest value represents ΔG* for Cu desorption for sandy soil in the presence of citric acid. The information in this study is quite necessary to construct full functioning models that will help scientists to better understand mobility and bioavailability of metals in soils.

Kinetics of copper desorption from soils as affected by different organic ligands

Desorption of Cu and low molecular weight dissolved organics are the primary factors that impact fate and transport of Cu in soils. To improve predictions of the toxicity and threat from Cu contaminated soil, it is critical that time-dependent desorption behavior be understood. In this paper, the effect of organic ligands citrate, malate, and succinate on the kinetics of Cu desorption from contaminated soils varying widely in soil characteristics was investigated at 25 0 C and the soils used were referred to as clay, calcareous and sandy soils. The amount of Cu released by the used organic ligands varied greatly with physicochemical properties of the soils. The rate of Cu release by different extractants was in the order citric > malic > succinic, which was consistent with the stability constants of Cu complexes with these ligands. The modified Freundlich and the Elovich and Parabolic diffusion models were used to describe dsorption of Cu 2+ from the three studied soils as affected by the organic ligands. All of the models fit the data well with correlation coefficients ranging from 0.83 to 1.00 (P < 0.01). Each Model has a set of assumptions for the different physical and chemical properties of the systems to which they are being applied. The uses of these equations yield different magnitudes for the calculated variable, but the relationships between the soil + organic ligands and their effect (i.e., increase or decrease) on these variables are the same. Such information is critical, since Cu is used in a variety of industrial and manufacturing processes and is one of the most common contaminants found at hazardous waste sites.

Desorption of copper and cadmium from soils enhanced by organic acids

The adsorption/desorption behavior of copper and cadmium on soils was investigated in this study. The adsorption isotherm of copper and cadmium conformed to Langmuir equation better than Freundlich equation. The effect of ionic strength, pH, and organic acid, including ethylenediamine tetraacetic disodium acid salt (EDTA), citric acid, oxalic acid and tartaric acid, on the desorption of copper and cadmium was studied. The desorption of copper and cadmium increased with the increase of ionic strength, while the desorption decreased with the rise of pH. The desorption of copper and cadmium enhanced by organic acids was influenced by pH. EDTA showed excellent enhancement on the desorption of both copper and cadmium; citric acid demonstrated great enhancement on the desorption of copper but negligible enhancement on the desorption of cadmium; oxalic acid enhanced the desorption of copper only at pH around 6.4 and enhanced the desorption of cadmium in the pH range from 6.4 to 10.7; tartaric acid slightly enhanced the desorption of copper but negligibly enhanced the desorption of cadmium. The desorption mechanism in the presence of organic acids were explained as the competition of complexation, adsorption and precipitation. The net effect determined the desorption efficiency. This study provided guidance for the selection of organic acids to enhance the electrokinetic (EK) remediation of copper and cadmium from contaminated soils.

Copper desorption from Gelidium algal biomass

Desorption of divalent copper from marine algae Gelidium sesquipedale, an algal waste (from agar extraction industry) and a composite material (the algal waste immobilized in polyacrylonitrile) was studied in a batch system. Copper ions were first adsorbed until saturation and then desorbed by HNO 3 and Na 2EDTA solutions. Elution efficiency using HNO 3 increases as pH decreases. At pH=1, for a solid to liquid ratio S/ L=4 g l −1, elution efficiency was 97%, 95% and 88%, the stoichiometric coefficient for the ionic exchange, 0.70±0.02, 0.73±0.05 and 0.76±0.06 and the selectivity coefficient, 0.93±0.07, 1.0±0.3 and 1.1±0.3, respectively, for algae Gelidium, algal waste and composite material. Complexation of copper ions by EDTA occurs in a molar proportion of 1:1 and the elution efficiency increases with EDTA concentration. For concentrations of 1.4, 0.88 and 0.57 mmol l −1, the elution efficiency for S/ L=4 g l −1, was 91%, 86% and 78%, respectively, for algae Gelidium, algal waste and composite material. The S/ L ratio, in the range 1–20 g l −1, has little influence on copper recovery by using 0.1 M HNO 3. Desorption kinetics was very fast for all biosorbents. Kinetic data using HNO 3 as eluant were well described by the mass transfer model, considering the average metal concentration in the solid phase and the equilibrium relationship given by the mass action law. The homogeneous diffusion coefficient varied between 1.0×10 −7 cm 2 s −1 for algae Gelidium and 3.0×10 −7 cm 2 s −1 for the composite material.

A Kinetic Model of Copper Cycling in San Francisco Bay

A two-dimensional, depth-averaged kinetic model of copper cycling was developed for the San Francisco Bay estuary. Adsorption and desorption reaction rate constants were determined from experimental sorption experiments. To calibrate the model, processes related to aqueous speciation were included. The model was used to predict spatial and seasonal trends in the adsorption and desorption of copper. Model predictions show that copper is continually being re-partitioned between sediment and water. Re-partitioning is prevalent near tributary and anthropogenic sources. It also occurs between segments of the bay, in response to differences in salinity and the availability of organic ligands dissolved in the water. In areas of restricted circulation such as the South Bay, copper adsorbed onto settling particles during wet season storm events acts as a source to the water column during the dry season. The relative contribution of resuspended benthic sediment to dissolved copper concentrations is highly variable in the bay. In the North Bay, dissolved copper is principally introduced from the San Joaquin-Sacramento Delta. In the South and lower South bays, desorption from sediment during the dry season may contribute as much as 20% of the total mass input of dissolved copper. Improvement of water quality can be achieved by reducing loads; however, changes are predicted to take years.

Kinetics of Copper Desorption from Highly Calcareous Soils

Desorption of copper (Cu) is an important factor in determining Cu availability in calcareous soils. Kinetics of native and added Cu desorption by DTPA (diethylene‐triaminepentaacetic‐acid) from 15 highly calcareous soils of southern Iran were studied in a laboratory experiment. Our results showed that two constant‐rate, Elovich, simple Elovich, and parabolic‐diffusion equations were the best‐fitted equations among eight kinetic models used. The copper desorption pattern based on the parabolic‐diffusion equation revealed that the rate of native Cu desorption was higher in the first 2 h followed by a slower release rate, which suggests that two different mechanisms are involved. The trend may describe why the DTPA soil test has been considerably successful in predicting Cu availability in calcareous soils. Stepwise multiple regression equations indicated that CCE (calcium carbonate equivalent), CEC (cation exchange capacity), and clay content are the most important soil characteristics that predict the rate constants of the kinetic models. Mean extractant recovery percentage (ERP) of the soils was only 20%, which indicated that after 20 days, DTPA extracted only one‐fifth of added Cu. Regression equations indicated that as soil OM (organic matter) content increased, the value of ERP decreased. From results reported herein it seems that CCE, CEC, and clay are the most important factors controlling Cu release from highly calcareous soils of southern Iran. However, the initial soil Cu desorption rate is probably controlled by CEC.

Adsorption and Desorption of Copper in Pasture Soils

Copper (Cu) is bound strongly to organic matter, oxides of iron (Fe) and manganese (Mn), and clay minerals in soils. To investigate the relative contribution of different soil components in the sorption of Cu, sorption was measured after the removal of various other soil components; organic matter and aluminum (Al) and Fe oxides are important in Cu adsorption. Both adsorption and desorption of Cu at various pH values were also measured by using diverse pasture soils. The differences in the sorption of Cu between the soils are attributed to the differences in the chemical characteristics of the soils. Copper sorption, as measured by the Freundlich equation sorption constants [potassium (K) and nitrogen (N)], was strongly correlated with soil properties, such as silt content, organic carbon, and soil pH. The relative importance of organic matter and oxides on Cu adsorption decreased and increased, respectively, with increasing solution Cu concentrations. In all soils, Cu sorption increased with increasing pH, but the solution Cu concentration decreased with increasing soil pH. The cumulative amounts of native and added soil Cu desorbed from two contrasting soils (Manawatu and Ngamoka) during desorption periods showed that the differences in the desorbability of Cu were a result of differences in the physico‐chemical properties of the soil matrix. This finding suggests that soil organic matter complexes of Cu added through fertilizer, resulted in decreased desorption. The proportions of added Cu desorbed during 10 desorption periods were low, ranging from 2.5% in the 24‐h to 6% in the 2‐h desorption periods. The desorption of Cu decreased with increasing soil pH. The irreversible retention of Cu might be the result of complex formation with Cu at high pH.

Competitive adsorption and desorption of copper and zinc in acid soils

As an aid to evaluating the environmental threat posed by Cu and Zn when both are present in acid soils, competitive and noncompetitive adsorption of Cu and Zn onto samples of the surface horizon of eight such soils was measured in batch experiments carried out at pH 5 with 0.01 M NaNO 3 as background electrolyte. Noncompetitive adsorption of Cu exceeded that of Zn, especially in the soils with greatest organic matter contents. These data were better fitted by the Freundlich equation than by the Langmuir equation, possibly due to the heterogeneity of the adsorbent surfaces. The Langmuir–Freundlich equation was not appropriate for these data: it could not be fitted to the Zn data, and when fitted to the Cu data the uncertainty in the values of its parameters was too large for them to be useful. Total metal adsorption from solutions containing Cu and Zn in 1 : 1 mole ratio was intermediate between adsorption from Zn and Cu solutions of the same total concentration, indicating competition between the two metals. Adsorption of Zn was severely depressed (in some soils almost completely) by the presence of increasing concentrations of Cu in the adsorption solution, but adsorption of Cu was depressed by at most 31% by the presence of increasing concentrations of Zn. Adsorption of Zn from solutions containing both Zn and Cu was modelled well by Murali and Aylmore's generalization of the Freundlich equation, but this equation reduced to the Freundlich equation itself when it was fitted to data for the adsorption of Cu from mixed solutions. Desorption of Cu into NaNO 3 solution from previously Cu-loaded soils in no case exceeded 11% of the Cu previously adsorbed, whereas analogous desorption of Zn was in all cases greater and ranged from 9% to 32%. Desorption of both Cu and Zn was greater when Cu was desorbed into Zn(NO 3) 2 and Zn into Cu(NO 3) 2.

Adsorption and desorption of copper and zinc in the surface layer of acid soils

The environmental and health effects of the contamination of soils by heavy metals depend on the ability of the soils to immobilize these contaminants. In this work, the adsorption and desorption of Cu and Zn in the surface layers of 27 acid soils were studied. Adsorption of Cu II from 157–3148 μmol L −1 solutions was much greater than adsorption of Zn II from solutions at the same concentration. For both Cu and Zn, the adsorption data were fitted better by the Freundlich equation than by the Langmuir equation. Multiple regression analyses suggest that Cu and Zn adsorption depends to a significant extent on pH and CEC: for both metals these variables accounted for more than 80% of the variance in the Freundlich pre-exponential parameter K F , and pH also accounted for 57% of the variance in 1 / n for Zn and, together with carbon content, for 41% of the variance in 1 / n for Cu. The percentage of adsorbed metal susceptible to desorption into 0.01 M NaNO 3 was greater for Zn than for Cu, but in both cases depended significantly on pH, decreasing as pH increased. In turn, both pH H 2O and pH KCl are significantly correlated with cation exchange capacity. Desorption of metal adsorbed from solutions at relatively low concentration (787 μmol L −1) exhibited power-law dependence on K d , the quotient expressing distribution between soil and soil solution in the corresponding adsorption experiment, decreasing as increasing K d reflected increasing affinity of the soil for the metal. The absence of a similarly clear relationship when metal had been adsorbed from solutions at relatively high concentration (2361 μmol L −1) is attributed to the scant between-soil variability of K d at these higher concentrations. In general, adsorption was greater and subsequent desorption less in cultivated soils than in woodland soils.

Effects of clay amendment on adsorption and desorption of copper in water repellent soils

Copper is an important micronutrient and trace amounts are essential for crop growth. However, high concentrations of copper will produce toxic effects. Australia is increasingly developing production of crops in water repellent soils. Clay amendment, a common amelioration techniques used in Australia, has demonstrated agronomic benefits in increased crop or pasture production. The sorption and desorption of copper and the effect of clay treatment on copper behaviour in a water repellent soil collected from an experimental farm in South Australia is studied. We found that the water repellent soils amended with clay have an increased adsorption capacity of copper. Also the clay-amended soils had an increased ratio of specific sorption to total sorption of copper. The implications of this study to the sustainable agro-environmental management of water repellent soils is discussed.

Continuous oxygen steelmaking with copper-, tin-, and zinc-contaminated scrap

In the context of a new zero-gas-emission process for continuous oxygen steelmaking, desorption of copper, tin, and zinc from liquid scrap are modeled. Additive diffusional-resistance concepts show that zinc elimination at atmospheric pressure is entirely straightforward. For copper and tin, a reduced pressure (2.5 mbar) and a relatively high temperature (1780 °C) are preferred. Sulfur must be added above the stoichiometric requirements to volatilize tin sulfide. Copper elimination by physical desorption is completely predictable, but with tin, interfacial chemical kinetics may possibly exert an influence. Based on exclusive transport control and the currently available pumping capacity for vacuum degassing steel, the engineering feasibility of refining continuously melted steel scrap is established. Dimensions are estimated for producing 2 Mtpa of steel with a scrap-to-virgin iron ratio of 3 to 1. Electrical conductive heating is required to raise the liquid-scrap temperature toward the limits imposed by current refractories. With the proposed new technology, copper, tin, and zinc are all recovered as by-product metals. Pretreatment of steel scrap is not advocated, other than simple physical segregation at the source.

Sorption–Desorption of Copper and Strontium Ions by the Soil. The Influence of Microorganisms on the State of Metals

Sorption of heavy metal (copper and strontium) ions by the meadow chernozem and grey forest soils differing in the content of organic substance was described using the Langmuir equation. The analysis of characteristic sorption coefficients demonstrated that copper possesses the enhanced affinity for the studied soil samples compared to strontium. Maximal values of the sorption of copper (0.085 mmol/g) and strontium (0.045 mmol/g) obtained for the colloidal fraction of meadow chernozem soil (particle diameter d < 1 μm) are approximately 1.5 times larger than for the same fraction of grey forest soil; this ratio remains almost the same even when using the coarser fraction (d < 50 μm). It was established that up to 90% of metal ions could be present in the soil in an immobile form. An increase in the concentration of heavy metal ions in the soil causes their redistribution between the components of absorbing soil complex and an increase in the fraction of metal in mobile forms (water-soluble, exchange, soluble in weakly acidic medium). Upon the microbiological treatment (bioleaching in the suspension variant) of the soils containing copper or strontium ions, the total content of metal, including its mobile forms, decreases by an order of magnitude.

Predicting the rate and extent of cadmium and copper desorption from soils in the presence of bacterial extracellular polymer

The movement of cationic transition metals through the subsurface is strongly retarded by sorption to the porous media. However, dissolved organic ligands can compete with soil surfaces by providing binding sites for metals in solution. An extracellular polymer produced by a bacterium isolated from soil was used in this study to observe and model the influence of a naturally occurring ligand on the release of adsorbed metals from two test soils. Experimental results show that the presence of dissolved extracellular polymer enhanced the rate and extent of desorptive release of soil-bound cadmium and copper. A kinetic model that uses a gamma distribution of rate constants to account for the physical and chemical heterogeneity of the soil matrix was employed to describe the release of cadmium and copper in batch experiments. Model parameters describing soil, metal and extracellular polymer interactions were obtained through separate experiments. With these parameters the model successfully predicted the influence of dissolved polymer on the rate and extent of release of cadmium and copper from soil in independent batch experiments. These results suggest that the presence of natural metal-binding ligands such as bacterial extracellular polymers can act to increase the driving force for desorption by lowering the aqueous concentration of free unbound metals in solution.

Predicting the rate and extent of cadmium and copper desorption from soils in the presence of bacterial extracellular polymer

The movement of cationic transition metals through the subsurface is strongly retarded by sorption to the porous media. However, dissolved organic ligands can compete with soil surfaces by providing binding sites for metals in solution. An extracellular polymer produced by a bacterium isolated from soil was used in this study to observe and model the influence of a naturally occurring ligand on the release of adsorbed metals from two test soils. Experimental results show that the presence of dissolved extracellular polymer enhanced the rate and extent of desorptive release of soil-bound cadmium and copper. A kinetic model that uses a gamma distribution of rate constants to account for the physical and chemical heterogeneity of the soil matrix was employed to describe the release of cadmium and copper in batch experiments. Model parameters describing soil, metal and extracellular polymer interactions were obtained through separate experiments. With these parameters the model successfully predicted the influence of dissolved polymer on the rate and extent of release of cadmium and copper from soil in independent batch experiments. These results suggest that the presence of natural metal-binding ligands such as bacterial extracellular polymers can act to increase the driving force for desorption by lowering the aqueous concentration of free unbound metals in solution.

Copper desorption in a soil with variable charge

Adsorption processes of heavy metals in soils have been more extensively studied than desorption, in spite of this latter process being related to nutrient bioavailability in the soil solution. Copper desorption from surface (0-0.2 m) and subsurface (1.0 - 1.2 m) samples of an Anionic Acrudox was studied at two pH values (4.5 and 7.5). Soil samples were incubated with Cu rates varying from 0 to 400 mg kg-1, during 4 and 12 weeks, in the presence of CaCl2 as support electrolyte at concentrations of 0.01 and 0.001 mol L-1. Complete soil adsorption of added Cu was observed at pH 7.5 in all incubation periods, indicating that a 24h-shaking period was enough to reach equilibrium and maximum adsorption. Copper adsorption varied with the incubation period and was much lower at pH 4.5 than at pH 7.5, after the 24 hour-incubation period. After 4 and 12 weeks, Cu adsorption values were higher and similar for all soil samples, irrespective of pH or depth of sampling. The effect of the incubation period on soil Cu adsorption surpassed the pH effect for all Cu rates. The hysteresis was expressive, suggesting that Cu enhances high-energy bonds with the soil colloids. Calcium chloride was not efficient in promoting native soil Cu desorption in the studied concentrations.

Competitive Adsorption and Desorption of Cadmium, Chromium, Copper, Nickel, Lead, and Zinc by Humic Umbrisols

The objective of this study was the evaluation of the selectivity sequences of adsorption and retention of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in four Humic Umbrisols from the province of Pontevedra, Spain. The characteristics of the surface horizons of the soils showed significant differences in the components and properties that influence adsorption capacity and mobility of metals and, therefore, their retention by the soils. The most adsorbent and retentive soil after desorption has the highest content of manganese (Mn), iron (Fe), and aluminum (Al) oxides. The least adsorbent has the lowest content of oxides and organic matter. The metal adsorbed in greater amount by the soils was Pb, followed by Cu and Cr, which competed favorably for adsorption sites with Cd, Ni, and Zn. After desorption, Cr is the most retained metal. The greater retention of Cr seems to indicate that the relation charge-to-radius is the most influential factor in the retention of this element. In general, the properties and components of the soils have more influence on the adsorption and retention of the metals than the properties of the metallic ions.

Competitive Adsorption and Desorption of Cadmium, Chromium, Copper, Nickel, Lead, and Zinc by Humic Umbrisols

Abstract The objective of this study was the evaluation of the selectivity sequences of adsorption and retention of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in four Humic Umbrisols from the province of Pontevedra, Spain. The characteristics of the surface horizons of the soils showed significant differences in the components and properties that influence adsorption capacity and mobility of metals and, therefore, their retention by the soils. The most adsorbent and retentive soil after desorption has the highest content of manganese (Mn), iron (Fe), and aluminum (Al) oxides. The least adsorbent has the lowest content of oxides and organic matter. The metal adsorbed in greater amount by the soils was Pb, followed by Cu and Cr, which competed favorably for adsorption sites with Cd, Ni, and Zn. After desorption, Cr is the most retained metal. The greater retention of Cr seems to indicate that the relation charge-to-radius is the most influential factor in the retention of this element. In general, the properties and components of the soils have more influence on the adsorption and retention of the metals than the properties of the metallic ions.