Desorption Of Cu Research Articles

The investigation of sorption-desorption performance and mechanism of copper by surfactant-modified zeolite in aqueous solutions.

As the most common filler in stormwater treatment, zeolite (NZ-Y) has good cation exchange capability and stabilization potential for the removal of heavy metal from aqueous solutions. In this study, sodium dodecyl sulfate (SDS) and NZ-Y were selected to preparing new adsorbent (SDS-NZ) by using a simple hydrothermal method. The sorption-desorption performance and mechanism of Cu(II) onto SDS-NZ were investigated. The results showed that the sorption of Cu(II) on SDS-NZ was in accordance with the pseudo-second-order kinetic model with an equilibrium time of 4h. The sorption behavior fitted Langmuir isotherm with a saturation sorption capability of 9.03mg/g, which was three times higher than that of NZ-Y. The modification of SDS increases the average pore size of NZ-Y by 3.96nm, which results in a richer internal pore structure and more useful sorption sites for Cu(II) sorption. There was a positive correlation between solution pH values and sorption capability of Cu(II) in the range of 3.0-6.0. With the ionic strength increased, the sorption capability of Cu(II) onto SDS-NZ first decreased and then increased, which may be attributed to competitive sorption and compression of the electronic layer. The desorption of Cu(II) on SDS-NZ was favored by the increase in SDS concentration and ionic strength and decrease in solution pH values. The application of SDS-NZ in runoff improved the leaching risk of Cu(II). After several cycles, the ability of reused SDS-NZ to efficiently adsorb most heavy metals was verified with removal rates above 99%.

Probe the Dynamic Adsorption and Phase Transition of Underpotential Deposition Processes at Electrode-Electrolyte Interfaces.

Electrochemical scanning tunneling microscopy (EC-STM) and electrochemical quartz crystal microbalance (E-QCM) techniques in combination with DFT calculations have been applied to reveal the static phase and the phase transition of copper underpotential deposition (UPD) on a gold electrode surface. EC-STM demonstrated, for the first time, the direct visualization of the disintegration of (√3 × √3)R30° copper UPD adlayer with coadsorbed SO42- while changing sample potential (ES) toward the redox Pa2/Pc2 peaks, which are associated with the phase transition between the Cu UPD (√3 × √3)R30° phase II and disordered randomly adsorbed phase III. DFT calculations show that SO42- binds via three oxygens to the bridge sites of the copper with sulfate being located directly above the copper vacancy in the (√3 × √3)R30° adlayer, whereas the remaining oxygen of the sulfate points away from the surface. E-QCM measurement of the change of the electric charge due to Cu UPD Faradaic processes, the change of the interfacial mass due to the adsorption and desorption of Cu(II) and SO42-, and the formation and stripping of UPD copper on the gold surface provide complementary information that validates the EC-STM and DFT results. This work demonstrated the advantage of using complementary in situ experimental techniques (E-QCM and EC-STM) combined with simulations to obtain an accurate and complete picture of the dynamic interfacial adsorption and UPD processes at the electrode/electrolyte interface.

Adsorption–desorption behavior of halloysite clay for Cu2+ ions and recovery of copper by electrodeposition method

Halloysite sample, obtained from Phu Tho province, Vietnam, was utilized to investigate the adsorption behavior of Cu2+ ions. Several factors influencing Cu2+ adsorption efficiency and capacity were explored, including pH value, contact time, adsorbent dose, and initial Cu2+ concentration. Under optimal conditions (0.8 g of halloysite per 50 mL of solution, an initial Cu2+ concentration of 40 mg/L, pH 6.2, a contact time of 80 min, and a temperature of 25 °C), the study yielded an adsorption efficiency of 85.19% and a capacity of 2.14 mg/g for Cu2+ ions. Adsorption isotherm analysis was conducted using the Langmuir and Freundlich models, while the kinetics of the adsorption process were investigated through the first-order pseudo and second-order pseudo models. Furthermore, the desorption of Cu2+ ions and the recovery of Cu metal were explored, with a recovery efficiency of Cu reaching 94.65% under suitable conditions (0.3 g mass of halloysite, a current of 7.5 mA, and an electrolytic time of 5 h at 60 °C). These findings suggest the potential application of halloysite clay for removing Cu2+ ions from polluted water, recovering Cu metal, and reusing the adsorbent.

Processes of Ion Exchange Sorption and Desorption of Cu2+ and Zn2+ Ions on a Composite Sorbent

Processes of Ion Exchange Sorption and Desorption of Cu2+ and Zn2+ Ions on a Composite Sorbent

Plasma preparation of highly reactive Ag-Cu NPs anchored in N-PC as catalysts for Aluminum-air battery

Efficient, stable and economical catalysts play a crucial role in enhancing the kinetics of slow oxygen reduction reactions (ORR) in Aluminum-air batteries. Among the potential next-generation candidates, Ag catalysts are promising due to their high activity and low cost, but weaker oxygen adsorption has hindered industrialization. To address this bottleneck, Ag-alloying has emerged as a principal strategy. In this work, we successfully prepared Ag-Cu nanoparticles (NPs) with a rich eutectic phase and uniform dispersion structure using plasma evaporation. The increased solid solution of Ag and Cu led to changes in the electronic structure, resulting in an upward shift of the d-band center, which significantly improved oxygen adsorption. The combination of Ag and Cu in the NPs synergistically enhanced the adsorption of Ag and the desorption of Cu. Density functional theory (DFT) calculations revealed that Ag-Cu25 NPs exhibited the smallest limiting reaction barrier, leading to increased ORR activity. To further optimize the catalyst's performance, we utilized N-doped porous nanocarbon (N-PC) with high electrical conductivity and abundant mesoporous channels as the support for the Ag-Cu NPs. The N-PC support provided optimal mass transfer carriers for the highly active Ag-Cu25 NPs. As a result, the Ag-Cu25/NPC catalyst displayed excellent ORR activity in alkaline media, with a half-wave potential (E1/2) of 0.82 V. Furthermore, the Al-air battery incorporating the Ag-Cu25/NPC catalyst exhibited outstanding electrochemical performance. It demonstrated high open-circuit voltages of 1.89 V and remarkable power densities of 193 mW cm−2. The battery also sustained a high current output and maintained a stable high voltage for 120 hours under mechanical charging, showcasing its significant potential for practical applications.

Adsorption of Pb(II), Hg(II) and Cu(II) ions on azacrown ether grafted chitosan films

The adsorption and desorption of Cu(II), Pb(II) and Hg(II) ions from aqueous solutions by porous azacrown ether grafted chitosan films (Ch-DAC) were studied in a batch adsorption system. The porous Ch-DAC films were prepared by hydroamination reaction of azacrown ether activated double bonds with chitosan by changing the proportion of Ch/DAC with 1:0, 1:0.125, 1:0.167, 1:0.25 and 1:0.5 ratios. Characteristics of the films such as pH of aqueous slurry, pH of zero-point charge (pHzpc), surface area and pore volume, energy dispersive X-ray spectroscopy (EDX), Field Emission - Scanning Electron Microscopy (FE-SEM), Fourier transform infrared (FTIR) were investigated. Factors influencing adsorption performance such as pH of the solution, metal ion concentration, adsorbent dosage and the DAC content were studied. Batch studies, investigating film adsorption capacity and adsorption isotherms for Pb(II), Hg(II) and Cu(II) ion adsorption equilibrium correlated well with Langmuir model. The maximum capacity for the adsorption of Pb(II), Hg(II) and Cu(II) ions calculated from the Langmuir isotherm was 256, 200 and 143 mg/g respectively. Compared with the pure non-grafted chitosan films, the azacrown ether films were proved to have better sorption performance for the Pb(II), Hg(II) and Cu(II) ions at pH 5 to 6.

Assessment of agricultural waste biochars for remediation of degraded water-soil environment: Dissolved organic carbon release and immobilization of impurities in one- or two-adsorbate systems

This paper presents a method of agricultural waste management — the production of two biochars (BC) from potato and raspberry stems. It defines the potential of these materials for remediation of degraded water and soil environments. The performed study included analyses of BC physicochemistry, dissolved organic carbon (DOC) release and ability to immobilize copper (Cu), tetracycline (TC) and carboxin (CB) in one- and two-adsorbate systems. The BCs were obtained with pyrolysis at 600 °C for 30 min in a nitrogen atmosphere. Their DOC was predominantly constituted of substances with large molecular weights and high aromaticity, meaning that both BCs can be safely applied as soil additives. Potato-biochar (P-BC) had a more developed surface than raspberry-biochar (R-BC). The specific surface area (SBET) of P-BC was 122 m2/g, whilst of R-BC was 87 m2/g. As a result, the efficiency of impurity adsorption in the one-adsorbate systems was higher for P-BC (61.75% for Cu, 73.84% for TC, and 54.43% for CB). In the two-adsorbate systems, organic impurities improved the immobilization of heavy metal ions on BCs. The efficiency of Cu adsorption on P-BC when TC was present was 88.29%. Desorption of Cu from BC was highest using HCl, whilst that of TC and CB was highest using NaOH. Maximum desorption was observed in a two-adsorbate system with TC + CB (up to 63.6% for TC). These results confirmed that potato and raspberry stems can be used to produce highly effective BCs with large application potential, especially for remediation of degraded soils and polluted waters.

Cu and As(V) Adsorption and Desorption on/from Different Soils and Bio-Adsorbents.

This research is concerned with the adsorption and desorption of Cu and As(V) on/from different soils and by-products. Both contaminants may reach soils by the spreading of manure/slurries, wastewater, sewage sludge, or pesticides, and also due to pollution caused by mining and industrial activities. Different crop soils were sampled in A Limia (AL) and Sarria (S) (Galicia, NW Spain). Three low-cost by-products were selected to evaluate their bio-adsorbent potential: pine bark, oak ash, and mussel shell. The adsorption/desorption studies were carried out by means of batch-type experiments, adding increasing and individual concentrations of Cu and As(V). The fit of the adsorption data to the Langmuir, Freundlich, and Temkin models was assessed, with good results in some cases, but with high estimation errors in others. Cu retention was higher in soils with high organic matter and/or pH, reaching almost 100%, while the desorption was less than 15%. The As(V) adsorption percentage clearly decreased for higher As doses, especially in S soils, from 60–100% to 10–40%. The As(V) desorption was closely related to soil acidity, being higher for soils with higher pH values (S soils), in which up to 66% of the As(V) previously adsorbed can be desorbed. The three by-products showed high Cu adsorption, especially oak ash, which adsorbed all the Cu added in a rather irreversible manner. Oak ash also adsorbed a high amount of As(V) (>80%) in a rather non-reversible way, while mussel shell adsorbed between 7 and 33% of the added As(V), and pine bark adsorbed less than 12%, with both by-products reaching 35% desorption. Based on the adsorption and desorption data, oak ash performed as an excellent adsorbent for both Cu and As(V), a fact favored by its high pH and the presence of non-crystalline minerals and different oxides and carbonates. Overall, the results of this research can be relevant when designing strategies to prevent Cu and As(V) pollution affecting soils, waterbodies, and plants, and therefore have repercussions on public health and the environment.

Adsorption and desorption of Cu, Zn, Pb, and Cd on surface sediments from a shallow lake, North China

The processes of adsorption and desorption of heavy metal ions on sediments is of great significance for water quality conservation. To investigate the adsorption and release characteristics of heavy metals on sediments from shallow lakes, an isothermal adsorption and desorption experiment of Cu2+, Zn2+, Pb2+, and Cd2+ on sediments from Baiyun Lake was carried out. Our results showed that sediments demonstrated a strong capacity of absorbing these heavy metal ions in a sorption system. The maximum sorption capacity for heavy metals on sediments followed the order Pb2+> Cd2+> Cu2+> Zn2+. The followed order of the maximum buffer capacities for heavy metals was Pb2+ > Cu2+ > Zn2+ > Cd2+. The Langmuir isotherms model can better fit the adsorption of Cu2+, whereas the Freundlich isotherm model for the adsorption of Zn2+, Pb2+, and Cd2+. In the maximum initial concentration treatment, Pb exhibited the highest desorption amount, followed by Cu and Zn, whereas the lowest amount of Cd was observed. The exponential and quadratic functions could describe the relationships of adsorption and desorption. In the maximum initial concentration treatment, the adsorption rates of these four heavy metals followed the order Pb2+ > Cd2+> Cu2+> Zn2+, whereas the desorption rates followed an opposite order. The hysteresis index (HI) values for Zn was smaller than 1, whereas the HI values for Cu and Cd were slightly larger than 1, suggesting slightly negative hysteresis processes. However, the HI value of Pb was larger than 1, indicating that Pb2+ was easily desorbed from sediments.

POLYDENTATE ADSORBENT BASED ON LINEN CELLULOSE MODIFIED BY HYPERBRANCHED POLYESTER POLYBENZOYLTHIOCARBAMATE

A highly efficient hybrid adsorbent based on an industrially available, biodegradable, non-toxic linencellulose modified with hyperbranched polyesterpolybenzoylthiocarbamate has been synthesized.The synthesis was carried out using as a linkertoluene diisocyanate.The second-generation hyperbranched polyesterpolybenzoylthiocarbamate according to 1H, 13C NMR and IR spectroscopy contains 8 terminal benzoylthiocarbamate and 8 hydroxyl groups.In the first stage, the reaction of toluene diisociant with linen cellulose was carried out. By potentiometric titration, the content of toluene diisociant was found to be 27%. Then, hyperbranched polyesterpolybenzoylthiocarbamate was added to the modified linen cellulose. The content of hyperbranched polymer in cellulose, determined by the weight method, is 5%. Unreacted isocyanate groups are neutralized with isobutyl alcohol. The structure of the hybrid material is proven by IR spectroscopy. The adsorption properties of the polydentate adsorbent were studied with respect to Cu(II) ions. It was found that the adsorption capacity of the adsorbent is 6.93 mg/g. Using DSC and TGA analysis, the temperature characteristics, thermal effects, and mass loss of the obtained polydentate compound and its complexes were determined.It was shown that in an acidic medium at pH 3-4, desorption of Cu (II) and Co (II) ions occurs with the regeneration of a hybrid adsorbent.

Preparation of a thermosensitive surface imprinted polymer based on palygorskite for removal of copper (II) from environment aqueous solution

ABSTRACT In this study, a new thermosensitive surface imprinted polymer based on palygorskite was successfully synthesised by a surface imprinting technique and used as an intelligent selective recognition adsorbent for the adsorption of Cu(II) ions from aqueous solution. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) measurements results demonstrated that Cu(II)-imprinted polymer was successfully synthesised. The separation and preconcentration characteristics of Cu(II)-imprinted polymer for Cu(II) were researched by batch and column procedures. optimal intelligent recognition temperature for adsorption is 35°C and intelligent identification and elution of Cu(II) can be achieved by adjusting the temperature. The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbents for Cu(II) was 35.55 and 9.78 mg g−1, respectively. The relative selectivity factor values (ar) of Cu(II)/Zn(II), Cu(II)/Ni(II), Cu(II)/Co(II) and Cu(II)/Pb(II) were 111.48, 85.37, 98.31 and 73.85 respectively, which were all greater than 1. The Cu(II)-imprinted polymer offered fast kinetics for the adsorption and desorption of Cu(II). Under the optimised conditions (pH-5, temperature-35°C, shaking time-15 min), a detection limit of 0.21 μg L−1 with a relative standard deviation (RSD) of 2.5% for Cu(II) was obtained. Based on Cu(II)-imprinted polymer packed columns, a highly selective pre-concentration method for Cu(II) was established. The accuracy of the method has been certified using national reference materials (GBW 08301). This method has also been successfully used for the determination of Cu (II) in locally collected water samples.

Temperature regulated adsorption and desorption of heavy metals to A-MIL-121: Mechanisms and the role of exchangeable protons

Adsorption is a viable technology to remove trace heavy metals from wastewater, but regeneration of adsorbents in an economic and environmentally friendly manner often represents a limiting factor of its application. Compared with traditional strong acid desorption, developing a chemical-free method is of great significance to both economic and the environmental welfare. Herein, we synthesized a novel thermoresponsive absorbent, A-MIL-121, which could effectively remove trace Cu(II) (> 95 %) from a high-salinity ([Na+]/[Cu2+] = 20000) water at normal temperature. At elevated temperature, A-MIL-121 could quickly and efficiently desorb Cu(II), with over 90% desorption rate at 80°C within 3 h. Fourier transform infrared spectroscopy (FTIR) analysis revealed that two types of –COOH groups existed in the material. One was in free form and acted as the sites for Cu(II) adsorption; the other was in dimer connected by two H-bonds, which cleaved at elevated temperature. As a result, massive exchangeable protons were released to the solution, which caused the desorption of Cu(II). Similar temperature dependent adsorption-desorption behavior was also found to other heavy metals, such as Cd2+, Pb2+, Ni2+. No significant capacity loss was observed after 10 successive adsorption-desorption cycles. Finally, Column experiments using a real copper electroplating wastewater showed that a total of ~ 1650 mL of clean water was generated before breakthrough (Cu2+ < 0.5 mg/L), while less than 45 mL of 80°C water was used for regeneration. This study indicates the potential of A-MIL-121 as a novel green adsorbent to address trace heavy metals in wastewater.

Effect of contamination sources on the rate of zinc, copper and nickel release from various soil ecosystems

Background and objectiveSoil is a substantive component in biosphere habitually endangered to superfluity contaminants particularly potential toxic elements (PTEs). The source of soil contaminants is very critical in controlling both their release and expected hazards in the different soil ecosystems. This study aims to investigate the effect of low-quality irrigation water (LQW) on the extent of soil pollution through desorption of zinc (Zn), nickel (Ni) and copper (Cu) from different polluted soils, collected from LQW irrigated farms for more than 40–80 years at Giza and Kafr-Elsheikh Governorates, Egypt.ResultsModels incorporated modified Freundlich (MFE), Elovich, first order and parabolic diffusion (PDE) showed significant results in describing the kinetic data under Egyptian conditions. Results entailed that according to the coefficient of determination (R2) and standard error, all used models well described the desorption of Cu, Ni and Zn, the most prevalent contaminants in the trailed soil ecosystems; for example, the R2 values were higher than 0.96** for zinc desorption using MFE model. As far as the PTEs levels are considered, the highest contaminant desorption rates were recorded at Kafr-Elsheikh site, followed by Kombora, and the lowest ones were in Abo Rawash soil ecosystem. The succession of more than one model to describe the kinetic perspective confirmed that the different mechanisms take place in PTEs sorption, distribution and subsequently release from different soil ecosystems.ConclusionsThe numerical values indicated that the soil ecosystems contaminated with industrial effluents were higher than those irrigated with sewage effluents regardless of the type of land use. More attention should be paid to low-quality water application in agriculture irrigation and its environmental risks.

Distribution of copper and zinc fractions in a Regosol profile under centenary vineyard

Phytosanitary treatments using Bordeaux mixture or zinc (Zn) fungicides are often used in vineyards, which increase soil copper (Cu) and Zn contents. In this study, the accumulation and distribution of Cu and Zn fractions (water soluble, exchangeable, oxidic, organic and residual fractions) was evaluated along a Regosol profile cultivated with vine since 1890 and treated with Bordeaux mixture. Copper and Zn contents of the superficial layer were around 2000 mg kg−1 and 170 mg kg−1, respectively, and decreased through depth profile. However, accumulation of these metals was also observed in deeper layers of the soil, until 50 cm depth. Most of the total Cu was bound to the mineral fraction, whereas Zn was predominantly in the residual one. In the superficial layer, the desorption potential was 25% for Cu and 46% for Zn of these metals total content. Although the dominance of chemical forms with low geochemical mobility, desorption of Cu and Zn occurs easily, representing a high risk of transference in the environment.

Kinetics of Aqueous Cu(II) Biosorption onto Thevetia peruviana Leaf Powder.

Copper is an essential micronutrient; however, as a result of its increasing demand, subsequent mining followed by its direct discharge into the environment has led to the contamination of our ecosystem. Thevetia peruviana (TP) is an ornamental herb of medicinal interest and is extensively used as an antipyretic and anticancer agent due to the presence of cardiac glycosides. In this work, we have explored the TP leaf powder as a biosorbent for Cu(II) removal from aqueous media and observed that it yields better results in comparison to other reported biosorbents for the removal of Cu(II). This work also emphasizes on the biosorption kinetics along with its plausible mechanism of interactions. The leaf powder characterized by FT-IR spectroscopy confirmed the diverse surface functionalities including hydroxyl, carbonyl, glycosides, etc. The morphology and elemental composition of the plant material have been investigated using SEM-EDAX analysis that confirms the heterogeneity and porosity of the biosorbent surface. The encouraging results revealed that the TP leaf powder could be used as a cost-effective biosorbent with an adsorption capacity of 187.51 mg g–1 for Cu(II) in aqueous media at pH ∼ 5 and a temperature of 303 K. The complex functionality of the TP surface most likely played a significant role in attaining fast equilibrium within 60 min by following pseudo-second-order kinetics, having a rate constant of 2 × 103 mg g–1 min–1 that has been confirmed with statistical tools such as regression coefficient, chi-squared, and sum of error square tests. The adsorption mechanism is controlled by diffusion of Cu(II) from the liquid phase to the solid phase of the TP biosorbent followed by the chemical interaction between the biosorbent and the adsorbate with slow intraparticle diffusion on the biosorbent surface. The adsorption of Cu(II) on TP has been observed to rise from 59.29 to 197.63 mg g–1 with the rise in the pH of the medium from 2 to 7. The adsorption of Cu(II) has been found to increase from 176.80 to 191.33 mg g–1 with increasing temperature from 293–308 K, confirming the endothermic nature of the adsorption process. The thermodynamic study revealed the adsorption process to be spontaneous with negative ΔG (−10.43 to −13.74 kJ mol–1) and that it has an endothermic nature with positive ΔH (54.24 kJ mol–1). The isotherm study for Cu(II) on TP followed the Langmuir adsorption isotherm model with the maximum monolayer adsorption capacity of 303.03 mg g–1 rather than Freundlich and Temkin isotherm models, which confirmed the chemical interaction between the sorbent and sorbate. FT-IR and SEM-EDAX analyses have also been used to confirm the adsorption of Cu(II) onto the TP surface. The present study revealed 99.7% Cu(II) desorption using 0.8 N HCl as the desorbent accompanied by a 69.71% regeneration efficiency of the TP biosorbent. After desorption of Cu(II), the regenerated TP could be disposed of in soil. The encouraging results revealed that TP could be used as an alternative and low-cost biosorbent for the removal of heavy metals from aqueous solutions.

Efficient use of algae biomass loaded with essential metal ions in the manufacture of feed additives

In this study, the biosorption and desorption of Cu(II), Co(II), and Zn(II) ions on biomass of the green alga Cladophora sericea was examined to highlight the potential use of this biomass in the manufacture of feed additives. The selection of Cu(II), Co(II), and Zn(II) ions for the experimental studies was done considering their importance for living organisms. Biosorption of metal ions on algal biomass was performed in batch systems, at different initial metal ion concentration and contact time, at pH 5.5, 8 g L−1 biomass dosage and room temperature (21 ± 1 °C). The isotherm and kinetic parameters obtained by modelling the experimental data were used to evaluate the efficiency of biosorption processes. The high values of maximum biosorption capacities (21.18 mg Cu(II) g−1; 14.18 mg Co(II) g−1; and 33.78 mg Zn(II) g−1) and low contact time (around 15 min) indicate the possible use of this biomass as metal ion carrier in the manufacture of feed additives. Desorption of retained metal ions from loaded algae biomass was also examined, as a function of contact time. For similarity with gastric juice, 10 mL of HCl (1 mM) was used as desorption agent. The experimental data indicate that the metal ion desorption takes place gradually in time, but the desorption efficiency did not exceed 51% for all studied metal ions, after 24 h of contact time. The low efficiency of desorption processes is undesirable in the manufacturing of feed additives, and to minimize this disadvantage, the addition of activated carbon (AC) is proposed in this study. Simple mixing of loaded algae biomass with AC in a mass ratio of 1:1 determines the increase of desorption efficiency for all studied metal ions and opens new possibilities for the use of enriched algae biomass in the manufacture of feed additives.

CNT-sorbents for heavy metals: Electrochemical regeneration and closed-loop recycling

Heavy metal contamination of aquatic environments is a major concern. Carbon nanotubes (CNTs) are among the most effective adsorbents for heavy metal removal due. However, their high cost and their uncertain environmental impact necessitates a closed-loop process through sorbent regeneration and recycling for practical application. Our work demonstrates heavy metal adsorption by carboxylic acid-functionalized single-walled/double-walled carbon nanotubes (f-SW/DWCNTs) and their regeneration using electric fields. We follow a multi-step process: 1) copper in an aqueous solution is adsorbed onto the surface of f-SW/DWCNTs, 2) the copper-saturated f-SW/DWCNTs are filtered onto a microfiltration (MF) membrane, 3) the f-SW/DWCNT coated membrane is used as an anode in an electrochemical cell, 4) an applied electric field desorbs the metals from the CNTs into a concentrated waste, and 5) the CNTs are separated from the membrane, re-dispersed and reused in copper-contaminated water for successive adsorption. With an applied positive electric potential, we achieved ∼90 % desorption of Cu from f-SW/DWCNTs. We hypothesize that the electric field generated at the anode causes electrostatic repulsion between the anode and the electrostatically adsorbed heavy metal ions. The effect of applied voltages, electrode spacing and electrolyte conductivity on the desorption of Cu from CNTs was also investigated.

Effect of dissolved organic matters on adsorption and desorption behavior of heavy metals in a water-level-fluctuation zone of the Three Gorges Reservoir, China

Operation of recession and inundation in Three Gorges Reservoir (TGR) revealed a potential contribution to the migration of heavy metals in soil and fluvial systems, thus led to negative ecological impacts. The work herein investigated the concentration and speciation of three typical heavy metals (Cd, Cr and Cu) in a water-level-fluctuation zone of TGR, as well as simulated the adsorption and desorption behavior of heavy metals on soils, which aimed at elucidating the fate of heavy metals in this special area. Field investigation revealed that water level fluctuation greatly enabled the migration of heavy metals to inner or upper soil layers. Laboratory experiments showed that adsorption of Cd(II) was a chemical process and dissolved organic matters (DOM) in soils strengthened the combination of Cd(II) to soil surface which inhibited the desorption process. Cr(VI) was physically adsorbed and readily to be desorbed. DOM enabled deposition of Cr(VI) in soils. Cation exchange was dominate mechanism in Cu(II) adsorption process, whereas DOM presented positive effects on desorption of Cu(II). The results presented in this study would provide basic theory for scientific research in TGR.

Mineral and chemical changes of sediments after Cu sorption and then desorption induced by synthetic root exudate

Understanding the fate of anthropogenically introduced copper in sediments is important to comprehend the biogeochemical processes; consequently, beneficial utilization of Cu-rich materials can be proposed (e.g. soil amendment). Therefore, we address the behavior of copper and other metals at the liquid-solid interface of different grain sizes in lake sediments. Initially, the sediment fractions were characterized for mineralogy (XRD), chemical structure (FTIR), physicochemical parameters (mainly pH, cation exchange capacity, and electric conductivity), organic content, and chemical composition (AAS). Then, solutions of varying Cu concentrations were added to the fractions; the Cu concentrations of the sorption experiment were chosen according to the exchangeable cations of each fraction. A desorption experiment by synthetic root exudate was followed. The physicochemical parameters, functional groups, and mineralogy were noted before and after the two experiments. The sorption and desorption of Cu, Ca, Mg, K, and Na were also studied. The sediment fractions had similar mineralogy and chemical structure, yet the physicochemical composition and metal contents were different. The Cu sorption experiment showed that surface Ca and embedded Mg were the main cations that were exchanged with Cu, as shown by linear and logarithmic trends, respectively. The copper-sediment interaction mainly occurred at the organic interface. Finally, synthetic root exudate was able to restore part of the initial chemical structure of the sediments, indicating exchangeable Cu sorption on the organic part of the sediments. The various grain sizes had an insignificant influence on the behavior of metal sorption and desorption.

Preparation of hydrogel composites using Ca2+ and Cu2+ ions as crosslinking agents

The aim of this work was to investigate the influence of the crosslinking agent on the production of biopolymer composites with immobilized eggshells. Capsules with various chemical composition were produced: pure alginate (ALG) and alginate with carboxymethylcellulose and different content of biosorbent (5 wt% and 10 wt%). Two crosslinking agents have been used for the production of composites, i.e. Cu2+ ions and Ca2+ ions. Physicochemical properties (drying kinetics, swelling) and sorption properties of the structures were examined. Composite functional groups responsible for binding Cu2+ cations using Fourier transform infrared spectroscopy were located. Desorption of Cu2+ ions was performed to investigate the effect of crosslinkers on the release of cations (composites crosslinked with Ca2+ ions slower desorb the Cu2+ ions). The results showed that the type of the crosslinking agent has a significant influence on the physicochemical properties of biocomposites, as well as the binding and release of Cu2+ ions. Based on the result, biocomposites with immobilized biomass crosslinked with Ca2+ ions could be used in the future as controlled release fertilizers.