Desorption Of Cu Research Articles

Case study on the strategy and application of enhancement solutions to improve remediation of soils contaminated with Cu, Pb and Zn by means of electrodialysis

Numerous studies have been conducted with electrochemical removal of heavy metals from spiked kaolinite. Meanwhile, when moving from kaolinite to real soils, new factors must be taken into account—factors influencing, e.g., the buffering capacity of the soil against acidification and the adsorption/desorption processes of the heavy metals. The present study gives some examples where it is necessary to use an enhancement solution to aid desorption of Cu, Zn and Pb during electrodialytic treatment. Dependent on the composition of the pollution, different choices can be made. In the case of a Cu-polluted calcareous soil, ammonia may be used as enhancement solution, due to the formation of charged complexes between ammonia and Cu. Thus, Cu is mobile at high pH when ammonia is added and Cu can be removed without dissolving the calcareous parts. Zn is also mobilized by ammonia, but to a lesser extent than Cu. In the case of Cu, Zn and Pb at the same time, alkaline ammonium citrate may be a solution. It was shown that this enhancement solution could mobilize these three pollutants, but optimization of concentration and pH of the ammonium citrate is still needed. When choosing a remediation scheme for electrochemical treatment of an actual industrially polluted soil, this scheme must be chosen on basis of characterization of soil and pollution combination.

Electrochemical Investigation of Binding of Heavy Metal Ions to Turkish Lignites

AbstractAdsorption and desorption of Cu2+, Pb2+, Cd2+, Ni2+ and Zn2+ ions on samples of lignites (young brown coal) from three areas in the vicinity of Konya (Anatolia, Turkey) were followed using the polarographic method of analysis. This method enables the determination of free metal ions in suspensions containing both small and colloidal particles of lignite. Effects of pH, nature of the metal ion, and origin of the lignite on its adsorption capacity were followed. Binding is only between 5 and 30% reversible, indicating that ion exchange is not the predominant factor. The role of the size and shape of cavities inside pulverized lignite and of the functional groups inside these cavities was considered.

Effects of low-molecular-weight organic acids and residence time on desorption of Cu, Cd, and Pb from soils

Effects of low-molecular-weight organic acids (LMWOAs) and residence time on desorption of Cu, Cd, and Pb from two typical Chinese soils were studied. Citric, malic, and acetic acids were chosen as representatives of LMWOAs commonly present in soils. CaCl 2 and NaNO 3 were used in desorption as they were main soil background electrolytes for comparison. Desorption of Cu, Cd, and Pb from both soils followed the descending order: citric acid > malic acid > acetic acid > CaCl 2 > NaNO 3, which was consistent with the order of stability of Cu–, Cd–, and Pb–LMWOAs complexes from large to small and ion exchange ability of Ca 2+ and Na +. Desorption of metals by inorganic salts decreased with increasing desorption solution pH. Whereas desorption of metals by LMWOAs showed different trend in response to pH change due to their different complexing abilities. Malic and acetic acids released less metals at low pH 3.1 compared with citric acid at pH 7, indicating that pH was not the dominant factor governing the release of metals. In addition, all LMWOAs desorbed more metals than inorganic salts, CaCl 2 and NaNO 3. Therefore, organic ligands played a dominant role in desorption of heavy metals. More metals were released from Jiangxi soil than from Heilongjiang soil due to lower soil pH, CEC, organic matter content and manganese oxide of Jiangxi soil. Generally, desorption of metals decreased with increasing residence time of metals in soils.

Mechanisms of lead, copper, and zinc retention by phosphate rock

The solid–liquid interface reaction between phosphate rock (PR) and metals (Pb, Cu, and Zn) was studied. Phosphate rock has the highest affinity for Pb, followed by Cu and Zn, with sorption capacities of 138, 114, and 83.2 mmol/kg PR, respectively. In the Pb–Cu–Zn ternary system, competitive metal sorption occurred with sorption capacity reduction of 15.2%, 48.3%, and 75.6% for Pb, Cu, and Zn, respectively compared to the mono-metal systems. A fractional factorial design showed the interfering effect in the order of Pb > Cu > Zn. Desorption of Cu and Zn was sensitive to pH change, increasing with pH decline, whereas Pb desorption was decreased with a strongly acidic TCLP extracting solution (pH=2.93). The greatest stability of Pb retention by PR can be attributed to the formation of insoluble fluoropyromorphite [Pb 10(PO 4) 6F 2], which was primarily responsible for Pb immobilization (up to 78.3%), with less contribution from the surface adsorption or complexation (21.7%), compared to 74.5% for Cu and 95.7% for Zn. Solution pH reduction during metal retention and flow calorimetry analysis both supported the hypothesis of retention of Pb, Cu, and Zn by surface adsorption or complexation. Flow calorimetry indicated that Pb and Cu adsorption onto PR was exothermic, while Zn sorption was endothermic. Our research demonstrated that PR can effectively remove Pb from solutions, even in the presence of other heavy metals (e.g. Cu, Zn).

Mechanisms of lead, copper, and zinc retention by phosphate rock

The solid–liquid interface reaction between phosphate rock (PR) and metals (Pb, Cu, and Zn) was studied. Phosphate rock has the highest affinity for Pb, followed by Cu and Zn, with sorption capacities of 138, 114, and 83.2 mmol/kg PR, respectively. In the Pb–Cu–Zn ternary system, competitive metal sorption occurred with sorption capacity reduction of 15.2%, 48.3%, and 75.6% for Pb, Cu, and Zn, respectively compared to the mono-metal systems. A fractional factorial design showed the interfering effect in the order of Pb > Cu > Zn. Desorption of Cu and Zn was sensitive to pH change, increasing with pH decline, whereas Pb desorption was decreased with a strongly acidic TCLP extracting solution (pH=2.93). The greatest stability of Pb retention by PR can be attributed to the formation of insoluble fluoropyromorphite [Pb10(PO4)6F2], which was primarily responsible for Pb immobilization (up to 78.3%), with less contribution from the surface adsorption or complexation (21.7%), compared to 74.5% for Cu and 95.7% for Zn. Solution pH reduction during metal retention and flow calorimetry analysis both supported the hypothesis of retention of Pb, Cu, and Zn by surface adsorption or complexation. Flow calorimetry indicated that Pb and Cu adsorption onto PR was exothermic, while Zn sorption was endothermic. Our research demonstrated that PR can effectively remove Pb from solutions, even in the presence of other heavy metals (e.g. Cu, Zn).

Soil pH and Anion Abundance Affects on Copper Adsorption

Copper (Cu) input to agricultural soils results from Cu containing pesticides and/or that in soil amendments, such as manure or sewage sludge. Soil and soil solution properties influence the adsorption and desorption of Cu by the soil, which in turn determines its plant availability and/or phytotoxicities. Effects of different anion enrichment in the equilibrium solution on Cu adsorption by different soils (pH range of 6.2–9.9) were investigated in this study over a range of Cu concentrations. With Cu concentrations in the range of 0–100 mg L−1 in the equilibration solution, 95–99% of applied Cu was adsorbed by all three soils. The adsorption of Cu was similar regardless of using either 0.01 M CaCl2 or Ca(NO3)2 as the equilibration solution. When the Cu concentration in the equilibration solution was further increased in the range of 500–2000 mg L−1, the adsorption of Cu decreased from 60 to 24% of applied Cu in two soils with pH 6.2–7.9. In a high pH soil (pH = 9.9), the Cu adsorption decreased from 77 to 34%. Addition of incinerated sewage sludge (ISS) to a Palouse silt loam soil (pH = 6.2) increased the Cu adsorption as compared to that by unamended soil. This was, in part, due to an increase in the soil suspension pH with ISS amendment.

Effects of organic acids on copper and cadmium desorption from contaminated soils

A study was conducted to investigate the effect of organic acids on Cd and Cu desorption from natural contaminated soils (NCS) with permanent contamination by metal smelters and from artificial contaminated soils (ACS) derived from an artificial amendment of Cd to three representative zonal soils in Central China. Results showed that the desorption of Cd in either NCS or ACS, with the increment of tartrate or citrate concentration in desorption solution, can be characterized as a valley-like curve. The presence of tartrate or citrate at a low concentration (≤0.5 mmol/l) inhibited Cd desorption from these two types of soils, whereas the presence of organic acids at high concentrations (≥2 mmol/l for citrate and about ≥15 mmol/l for tartrate) apparently promoted Cd desorption. The desorption curve of Cu by tartrate solution with different tartrate concentrations can also be characterized as a valley-like curve, while the desorption of Cu in the presence of citrate was directly enhanced with the increment of citrate concentration. With the enhancement of initial pH value from 2 to 8 in the presence of citrate, Cu desorption ratio decreased at the first stage, then increased, and then decreased again. A valley and a peak sequentially appeared in the Cd or Cu desorption curve with initial pH value increment. Compared with citrate, the desorption ratio of Cd or Cu from NCS or ACS was directly decreased in the presence of tartrate, with the enhancement of the pH value from 2 to 8. Cd or Cu desorption was clearly enhanced when the electrolyte concentration of KNO 3 or KCl increased in the presence of 2 mmol/l tartrate. Moreover, a higher desorption ratio of Cd or Cu was shown with KCl electrolyte than with KNO 3 electrolyte with the same concentration. Based on these observations, we suggest that bioavailabilities of heavy metal can be promoted with selected suitable types and concentrations of organic acid amendment and reasonable field condition.

Toxicity and bioaccumulation of copper in three green microalgal species.

The effective concentrations of copper on the inhibition of the growth of Scenedesmus obliquus, Chlorella pyrenoidosa and Closterium lunula at 96 h (96 h EC50) were determined to be 50, 68 and 200 microg/l, respectively. The low initial bioaccumulation of Cu by C. lunula was found to be responsible for its tolerance to Cu. The amount of Cu accumulated by all three microalgae reached the maximum value and decreased quickly after the peak followed by a slow decrease over the next 6 d. Bioaccumulation of Cu by C. lunula was directly proportional to the initial Cu concentration. After reaching the first peak after 1 d, the bioconcentration factor of Cu by microalgae declined to its minimum value during the exponential growth phase but increased in the stationary growth phase again. This indicates that desorption of Cu from microalgae was higher during the exponential growth phase but lower in the stationary growth phase. Smaller microalgae with low 96 h EC50 values are more efficient in removing Cu from wastewater.

The importance of organic matter distribution and extract soil:solution ratio on the desorption of heavy metals from soils.

The lability (mobility and bioavailability) of metals varies significantly with soil properties for similar total soil metal concentrations. We studied desorption of Cu, Ni and Zn, from 15 diverse, unamended soils. These studies included evaluation of the effects of soil:solution extraction ratio and the roles of soil properties on metal desorption. Dcsorption was examined for each metal by computing distribution coefficients (Kd) for each metal in each soil where Kd = [M]soil/[M]solution, Results from soil:solution ratio studies demonstrated that Kd values for the metals tended to increase with increasing soil:solution ratio. This result also held true for distribution of soil organic matter (SOM). Because the soil:solution ratio has a significant effect on measured metal distributions, we selected a high soil:solution ratio to more closely approach natural soil conditions. Copper showed strong affinity to operationally defined dissolved organic matter (DOM). In this study, DOM was operationally defined based on the total organic carbon (TOC) content in 0.45-microm or 0.22-microm filtrates of the extracts. The Kd of Cu correlated linearly (r2 = 0.91) with the Kd of organic matter (Kd-om) where the Kd-om is equal to SOM as measured by Walkley-Black wet combustion and converted to total carbon (TC) by a factor of 0.59. These values representing solid phase TC were then divided by soluble organic carbon as measured by TOC analysis (DOM). The conversion factor of 0.59 was employed in order to construct Kd-om values based on solid phase carbon and solution phase carbon. SOM plays a significant role in the fate of Cu in soil systems. Soil-solution distribution of Ni and Zn, as well as the activity of free Cu2+, were closely related to SOM, but not to DOM. Kd values for Ni, Zn and free Cu2+ in a particular soil were divided by the SOM content in the same soil. This normalization of the Kd values for Ni, Zn, and free Cu2+ to the SOM content resulted in significant improvements in the linear relationships between non-normalized Kd values and soil pH. The semi-empirical normalized regression equations can be used to predict the solubility of Ni and Zn and the activity of free Cu2+ as a function of pH.

Adsorption and chemical reaction of Cu(hfac)(vtms) on Cu(1 1 1)

We have investigated the adsorption and reaction of Cu(hfac) (vtms) (hexafluoroacetylacetonate, hfac; vinyl trimethyl silane, vtms) on a Cu(111) surface. The recombinative desorption of Cu(hfac)(vtms) and disproportionation reaction between adsorbed Cu(hfac) molecules were observed to occur between 240 and 400 K. The adsorption geometries of Cu(hfac) on Cu(111) have been also calculated by means of the extended Hückel method. It is found that the standing Cu(hfac) is more stable and favored for a cleavage of Cu–O bonds than the lying-down Cu(hfac) on the Cu(111) surface.

Partitioning of heavy metals between estuarine sediments and dissolved phase as a function of salinity, pH and time (Scheldt estuary)

The distribution coefficient (Kd) and kinetics of the heavy metals Cd, Cu, Zn and Pd as a function of salinity and pH are investigated experimentally considering desorption processes and adsorption of 109Cd radiotracer for natural particulate matter from the Scheldt estuary (Belgium/The Nitherlands). The desorption of Cu from polluted estuarine sediments is very low. Only at high salinities minor desorption was detected. At persistently low pH (<4), desorption was completed to 100 %. Also the Pb desorption is very limited and only strong acidification of the solution will efficiently desorb a considerable fraction of the element. The desorption of Cd is significant as a function of all the considered parameters. The desorption process is fast and up to 60 % of the adsorbed Cd can be released into natural water. Both the salinity and the pH can change the distribution between the solid and the dissolved phase significantly. The extent of Zn desorption is intermediate between Cd and Pb. Both salinity and pH are important parameters to be considered for the sorption processes in the natural environment. The adsorption of 109Cd on natural particulate matter from the Scheldt estuary changes as a function of temperature, salinity and composition of the particulate matter. The temperature has only a minor influence on the Kd-salinity relation, while the composition of the suspended matter showed to be very important. Even though the number of samples used was small, preliminary results show that organic content of sediments may be the most important parameter for adsorption of Cd. A similar relation between the Kd of the adsorption process using 109Cd and the desorption process as a function of salinity, indicates that the metal binding character of the adsorbed 109Cd may be identical to that of the naturally bound Cd released during the desorption process. The magnitude of the Kd, however, needs to be determined according to the different environmental parameters.

Sorption and Desorption of Cu and Cd by Microalgae.

Sorption and Desorption of Cu and Cd by Microalgae.

In Situ Observation of the Potential-Dependent Chemical State and Structure of a Cu Monolayer Deposited on the Surface of Carbon-Supported Platinum Clusters

A complete electrochemical oxidation−reduction cycle for a Cu monolayer on carbon-supported Pt clusters in alkaline solution has been monitored in situ by X-ray absorption spectroscopy. No desorption of Cu was observed upon oxidation. Near-range order and oxidation state of the Cu layer as a function of potential was obtained by in situ X-ray absorption spectroscopy. In contrast to bulk copper, the adsorbed copper monolayer transforms directly from the reduced state to Cu2+ and from the oxidized form to Cu0. Adsorption of OH- ions on the Cu layer was observed for potentials below those for the Cu0 → Cu2+ and Cu2+ → Cu0 transitions.

Optimization of flow rate, initial metal ion concentration and biomass density for maximum removal of Cu2+ by immobilized Microcystis

The potential of alginate-immobilized Microcystis packed in a column for maximum removal of Cu2+ at different flow rates, biomass, and initial metal ion concentration was assessed in a continuous flow system. Although Cu2+ removal did occur at all the flow rates tested, it was maximum (54%) at 0.75-ml min−1 flow rate, 30 μg ml−1 initial metal ion concentration and 0.016 g biomass. Cu2+ removal was influenced by inlet metal ion concentration and biomass density. An increase in the biomass concentration from 0.016 to 0.128 g resulted in an apparent increase in percentage removal but the Cu2+ adsorbed per unit dry wt. declined. When the flow rate (0.75 ml min−1) and biomass density (0.064 g) were kept constant and the inlet metal ion concentration was varied from 10 to 150 μg ml−1, a 68% removal of Cu2+ was obtained at 50 μg ml−1 initial concentration in a time duration of 15 min. The metal-laden columns were efficiently desorbed and regenerated following elution with double distilled water (DDW) (pH 2) (89%). This was followed by 1 mm EDTA > 1 mm NTA > 0.1 mm EDTA > 1 mm HCl > 1 mm HNO3 > 5 mm CaCl2 > DDW (pH 7.0) > 1 mm NaHCO3 > 1 mm CaCl2. Of the total (2.83 mg) adsorbed Cu2+, 1.89 mg (67%) was desorbed by DDW (pH 2) within the first 20 min of elution time. Thereafter the desorption rate slowed down and only 22% (0.632 mg) desorption was obtained in the last 20 min. In contrast to water pH 2, the desorption of Cu2+ by 1 mm EDTA was very slow, the maximum being 8% after 40 min of elution.

Effect of complexing agents on liquid-phase adsorption and desorption of copper(II) using chitosan

The effect of complexing agents on adsorption and desorption of Cu(II) from aqueous solutions using chitosan was investigated. Three complexing agents were used including EDTA (ethylenediaminetetraacetic acid), citric acid, and tartaric acid. It was shown that the isotherm data could be fitted by the Langmuir equation under a limited concentration range. Furthermore, the adsorption processes were analyzed by an intraparticle diffusion model and the rate parameters of intraparticle diffusion for Cu(II) adsorption could be correlated with the initial Cu(II) concentrations. Finally, the desorption of Cu(II) and its complexes from the loaded chitosan was tested using complexing agent solutions. Under comparable conditions, tartaric acid solution gave the best desorption efficiency. © 1999 Society of Chemical Industry

Effect of complexing agents on liquid‐phase adsorption and desorption of copper(II) using chitosan

The effect of complexing agents on adsorption and desorption of Cu(II) from aqueous solutions using chitosan was investigated. Three complexing agents were used including EDTA (ethylenediaminetetraacetic acid), citric acid, and tartaric acid. It was shown that the isotherm data could be fitted by the Langmuir equation under a limited concentration range. Furthermore, the adsorption processes were analyzed by an intraparticle diffusion model and the rate parameters of intraparticle diffusion for Cu(II) adsorption could be correlated with the initial Cu(II) concentrations. Finally, the desorption of Cu(II) and its complexes from the loaded chitosan was tested using complexing agent solutions. Under comparable conditions, tartaric acid solution gave the best desorption efficiency. © 1999 Society of Chemical Industry

Sorption and Desorption of Copper on Soil Clay Components

AbstractToxic effects have been reported due to the accumulation of Cu in soils receiving long‐term applications of swine (Sus scrofa) manure, sewage, municipal composts, and mining waste. The objective of this study was to quantify sorption and desorption of Cu on various clay and clay‐organic matter fractions separated from a Zook soil (fine, smectitic, mesic Cumulic Vertic Endoaquolls) located in central Iowa. The clay was separated into four particle‐size fractions and portions of each fraction were treated with H2O2 and/or dithionite‐citrate‐bicarbonate (DCB) for removal of organic matter and free‐iron compounds, respectively. A batch‐equilibration technique was employed to evaluate sorption of Cu at pH 6.0 in the presence of 0.01 M CaCl2. The sorption isotherms show that Cu was preferentially sorbed on organic matter associated with the coarse clay fraction of the soil. After removal of organic matter, the fine clay (<0.02 µm) exhibited higher Cu retention than did the coarse (0.2–2.0 µm) and medium clay (0.02–0.2 µm). The DCB treatment created or exposed high‐affinity sites for Cu on the fine clay, but had little effect on Cu sorption for the coarse day. Copper appears to be specifically sorbed on the surfaces of silicate clays in excess of that which can be accounted for by variable charge sites. The results also suggest that Fe oxides may coat lateral surfaces of layer silicates, blocking access of Cu to potential sorption sites. Substantial sorption‐desorption hysteresis was observed for all samples, suggesting that Cu forms high‐energy bonds with both organic matter and layer‐silicate surfaces.

Adsorption of Copper(II) by “Waste” Fe(III)/Cr(III) Hydroxide from Aqueous Solution and Radiator Manufacturing Industry Wastewater

“Waste” Fe(III)/Cr(III) hydroxide has been used as an adsorbent for the effective removal of copper from aqueous solution. The parameters studied include agitation time, Cu(II) concentration, adsorbent dose, temperature, and pH. The percent adsorption of Cu(II) increased with a decrease in the concentration of Cu(II) and an increase in temperature. Quantitative removal of Cu(II) by 50 mg/50 mL adsorbent was observed at pH 5.0 for a Cu(II) concentration of 40 mg/L. The equilibrium data fit well with the Langmuir isotherm. The adsorption capacity (Q 0) calculated from the Langmuir isotherm was 92.59 mg/g at an initial pH of 5.0 at 32°C. Desorption of Cu(II) from a Cu(II)-loaded adsorbent was 55.4% at pH 3.0. Application of the adsorbent for the removal of Cu(II) was successfully demonstrated using radiator manufacturing industry wastewater.

The Effect Of Surface Oxides On Cu/Ta Interfacial Interactions

AbstractWe report results of Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) studies under ultra high vacuum (UHV) conditions which demonstrate that even submonolayer coverages of oxygen on Ta significantly degrade the strength of Cu/Ta chemical interactions, and affect the kinetics of Cu diffusion into bulk Ta. On clean Ta, monolayer coverages of Cu will de-wet only above 600 K. A partial monolayer of adsorbed oxygen (3L O2 at 300 K) results in a reduction of the de-wetting temperature to 500 K, while saturation oxygen coverage (10 L O2, 300 K) results in de-wetting at 400 K. Diffusion of Cu into the Ta substrate at 1100 K occurs only after a 300-second induction period at this temperature. The induction period increases to 600 sec for partially oxidized Ta and to 1200 sec for saturation oxygen coverage. TPD studies indicate no desorption of Cu for temperatures below 1300 K. The higher desorption temperature of Cu (compared to the 1150 K sublimation temperature) indicates that all the Cu originally deposited is now chemically bound to Ta.

Decoration of steps at Pt single crystal electrodes and its electrocatalytic effect

Preferential blockage of step sites by Cu and Sn of a Pt(332) and Pt(755) electrode is achieved by partial desorption of full monolayers. In the case of Pt (332), desorption of Cu from terrace sites is of 0th order. Probably due to the regular arrangement of Sn atoms, the Pt (332) electrode partially covered by Sn shows a remarkable catalytic effect on CO oxidation.