Equilibrium and kinetics studies of Cu(II) ions adsorption on polyamidoamine dendrimer starch

A polyamidoamine dendrimer starch (PSt) was prepared with epichlorohydrin as cross-linking agent and characterized by FTIR and scanning electron microscopy. The adsorption behavior of PSt for Cu(II) ions was then studied. Effects of adsorption time, initial concentration of Cu(II) ions, and temperature on the adsorption of Cu(II) ions by PSt were researched, and the equilibrium, kinetics and thermodynamics of the adsorption process were further investigated. The results showed that PSt can effectively adsorb Cu(II) ions from the solution. The adsorption process can be well described by Langmuir isotherm and Freundlich isotherm, and the maximum adsorption capacities of G1PSt, G2PSt, and G4PSt were 3.0571, 3.4228, and 3.9527 mmol/g, respectively. The adsorption of Cu(II) ions on PSt was endothermic in nature. In addition, the pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. The pseudo-second-order kinetic model provided a better correlation of the experimental data in comparison with the pseudo-first-order model.     

Thermodynamics and kinetics of adsorption of Cu(II) from aqueous solutions onto multi-walled carbon nanotubes

Release of heavy metals into water as a result of industrial activities may pose a serious threat to the environment. The objective of this study is to assess the uptake of Cu²⁺ from aqueous solutions onto multi-walled carbon nanotubes (MWCNT). The potential of the t-MWCNT to remove Cu²⁺ cations from aqueous solutions was investigated in batch reactor under different experimental conditions. The processing parameters such as initial concentration of Cu²⁺ ions, temperature, and adsorbent mass were also investigated. Copper uptake was quantitatively evaluated using the Langmuir, Freundlich and Dubinin–Kaganer–Radushkevich (DKR) models. In addition, the adsorption equilibrium was described well by the Langmuir isotherm model with maximum adsorption capacity of 12.34 mg/g of Cu²⁺ cations on t-MWCNT. Various thermodynamic parameters, such as ΔG⁰, ΔH⁰ and ΔS⁰ were calculated. The thermodynamics of Cu²⁺ cations adsorption onto t-MWCNT system pointed at spontaneous and endothermic nature of the process. Using the second-order kinetic constants, the activation energy of adsorption (E_a) was determined as 27.187 kJ/mol according to the Arrhenius equation.     

Thermodynamics and kinetics of adsorption of Cu(II) from aqueous solutions onto a new cation exchanger derived from tamarind fruit shell

A novel cation exchanger (TFS-CE) having carboxylate functionality was prepared through graft copolymerization of hydroxyethylmethacrylate onto tamarind fruit shell (TFS) in the presence of N,N′-methylenebisacrylamide as a cross-linking agent using K₂S₂O₈/Na₂S₂O₃ initiator system, followed by functionalisation. The TFS-CE was used for the removal of Cu(II) from aqueous solutions. At fixed solid/solution ratio the various factors affecting adsorption such as pH, initial concentration, contact time, and temperature were investigated. Kinetic experiments showed that the amount of Cu(II) adsorbed increased with increase in Cu(II) concentration and equilibrium was attained at 1 h. The kinetics of adsorption follows pseudo-second-order model and the rate constant increases with increase in temperature indicating endothermic nature of adsorption. The Arrhenius and Eyring equations were used to obtain the kinetic parameters such as activation energy (E_a) and enthalpy (ΔH^#), entropy (ΔS^#) and free energy (ΔG^#) of activation for the adsorption process. The value of E_a for adsorption was found to be 10.84 kJ · mol^?1 and the adsorption involves diffusion controlled process. The equilibrium data were well fitted to the Langmuir isotherm. The maximum adsorption capacity for Cu(II) was 64 · 10 mg · g^?1 at T = 303 K. The thermodynamic parameters such as changes in free energy (ΔG^°), enthalpy (ΔH^°), and entropy (ΔS^°) were derived to predict the nature of adsorption process. The isosteric heat of adsorption increases with increase in surface loading indicating some lateral interactions between the adsorbed metal ions.     

Removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions by adsorption onto natural bentonite

In this study, the removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions using the adsorption process onto natural bentonite has been investigated as a function of initial metal concentration, pH and temperature. In order to find out the effect of temperature on adsorption, the experiments were conducted at 20, 50, 75 and 90 °C. For all the metal cations studied, the maximum adsorption was observed at 20 °C. The batch method has been employed using initial metal concentrations in solution ranging from 15 to 70 mg L⁻¹ at pH 3.0, 5.0, 7.0 and 9.0. A flame atomic absorption spectrometer was used for measuring the heavy metal concentrations before and after adsorption. The percentage adsorption and distribution coefficients (K _d) were determined for the adsorption system as a function of adsorbate concentration. In the ion exchange evaluation part of the study, it is determined that in every concentration range, adsorption ratios of bentonitic clay-heavy metal cations match to Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (DKR) adsorption isotherm data, adding to that every cation exchange capacity of metals has been calculated. It is shown that the bentonite is sensitive to pH changes, so that the amounts of heavy metal cations adsorbed increase as pH increase in adsorbent-adsorbate system. It is evident that the adsorption phenomena depend on the surface charge density of adsorbent and hydrated ion diameter depending upon the solution pH. According to the adsorption equilibrium studies, the selectivity order can be given as Zn²⁺>Cu²⁺>Co²⁺. These results show that bentonitic clay hold great potential to remove the relevant heavy metal cations from industrial wastewater. Also, from the results of the thermodynamic analysis, standard free energy ΔG ⁰, standard enthalpy ΔH ⁰ and standard entropy ΔS ⁰ of the adsorption process were calculated.     

Thermodynamic studies of Ni(II) adsorption onto bentonite from aqueous solution

The adsorption behavior of Ni(II) onto bentonite was studied as a function of temperature under optimized conditions of shaking time, amount of adsorbent, pH, and concentration of the adsorbate. Thermodynamic parameters such as ΔH^°, ΔS^°, and ΔG^° were calculated from the slope and intercept of the linear plot of lgK_D against 1/T. Analysis of adsorption results obtained at T=(298, 303, 313, and 323) K showed that the adsorption pattern on bentonite followed the Langmuir, Freundlich, and D-R isotherms. A flame atomic absorption spectrophotometer was used for measuring the concentration of Ni(II).     

Adsorption of Cu(II) and Zn(II) ions from aqueous solutions onto fine powder of Typha latifolia L. root: kinetics and isotherm studies

Fine powder of Typha latifolia L. root was used for adsorption of copper and zinc ions from buffered and nonbuffered aqueous solutions. The adsorption reached equilibrium in 60 min. During this time, more than 90 % of the adsorption process was completed. The effect of initial pH, initial concentration of metal ion, and contact time was investigated in a batch system at room temperature. The optimum adsorption performance was observed at pH 5.00 and 4.25 for nonbuffered solutions of Cu(II) and Zn(II), respectively, while for buffered solutions it occurred at pH 6.00. The total metal uptake decreased on application of ammonium acetate buffer, from 37.35 to 17.00 mg g^?1 and 28.80 to 9.90 mg g^?1 for Cu(II) and Zn(II) solutions, respectively, with 100 mg L^?1 initial concentration. The pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models were used to describe the adsorption kinetics. The experimental data followed the pseudo-second-order kinetic model. The biosorption equilibrium was well described by Langmuir and Freundlich isotherm models.     

Modeling adsorption of copper (II) onto fly ash and bentonite complex from aqueous solutions

Transportation of copper (II) ions from aqueous solutions to a fly ash and bentonite complex amorphous heterogeneous oxides (AHO: CaO-SiO(2)-Al(2)O(3)-MgO-FeO) system was studied. The particles of the fly ash and bentonite complex AHO system were highly porous and composed of platelike grains. They provide the physical basis for establishing a liquid-solid reaction model applicable to mesoporous solids. The main innovation of this model was in simplifying the powder granules to aggregates of close particles, while the particles act in accordance with the model better. The calculated curves from the models were well in line with the experimental results.     

Equilibrium studies of the sorption of Cu(II) ions onto chitosan

Chitosan is a polymer that can be obtained from the shells of seafood such as prawns, crabs, and lobsters. Chitosan has free amino groups, which can attract metal ions, and has been used as an adsorbent for the removal of metal ions from effluents. In this research, the sorption of copper ions from solution onto chitosan at two pHs has been investigated. DSC, TGA, surface area, SEM, and NMR studies have been used to report the pure physical states of chitosan and the chitosan-copper complex. The experimental isotherm data were analyzed using the Langmuir, Freundlich, and Redlich-Peterson equations. Correlation coefficients were determined for each isotherm analysis. Error functions have been used to determine the alternative single component parameters by nonlinear regression due to the inherent bias in using the correlation coefficient resulting from linearization. The error function method provided the best parameters for the isotherm equations in this system and is demonstrated for error comparison purposes.     

Cu(II) adsorption from aqueous solutions using the inner and outer portions of sugarcane bagasse

In the present work, the adsorption capacity of internal and external portions of treated sugarcane bagasse (SCB) to remove Cu(II) from aqueous solution was evaluated. In order to reuse this solid waste as an effective adsorption material, both portions were treated with three different solutions (hot water, ethanol and NaOH) to remove sugar, external gummy tissue and impurities. Adsorption experiments were carried out in a batch system at room temperature. The kinetic data were fitted to pseudo-second order and Elovich models for the internal portion, and to the Elovich model for the external portion reaching equilibrium times from 8 to 24 h. Freundlich and Langmuir–Freundlich models described well the adsorption behavior of all systems. The compositional differences of the two portions of SCB and the surface chemistry were analyzed. Material characterization by scanning electron microscopy, Fourier transformed infrared spectroscopy, and X-ray photoelectron spectroscopy demonstrated morphologic and chemical modifications of the material after each treatment. Results showed that external SCB treated with a sodium hydroxide solution and internal SCB treated with ethanol solution were the best adsorbent materials, and provided a surface with more affinity to remove Cu(II).     

Equilibrium and kinetics study of Gd(III) and U(VI) adsorption from aqueous solutions by modified Sorrel’s cement

Modified Sorrel’s cement was prepared by the addition of ferric chloride. The modified cement (MF5) was analyzed and characterized by different methods. Adsorption of Gd(III) and U(VI) ions in carbonate solution has been studied separately as a function of pH, contact time, adsorbent weight, carbonate concentration, concentration of Gd(III) and U(VI) and temperature. From equilibrium data obtained, the values of Δ H, Δ S and Δ G were found to equal −30.9 kJ ⋅ mol⁻¹, −85.4 J ⋅ mol⁻¹ ⋅,K⁻¹, and −5.4 KJ ⋅ mol⁻¹, respectively, for Gd(III) and 18.9 kJ ⋅ mol⁻¹, 67.8 J ⋅ mol⁻¹ K⁻¹ and −1.3 KJ ⋅ mol⁻¹, respectively, for U(VI). The equilibrium data obtained have been found to fit both Langmuir and Freundlich adsorption isotherms. The batch kinetic of Gd(III) and U(VI) on modified Sorrel’s cement (MF5) with the thermodynamic parameters from carbonate solution were studied to explain the mechanistic aspects of the adsorption process. Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Various parameters such as effective diffusion coefficient and activation energy of activation were evaluated. The adsorption of Gd(III) and U(VI) on the MF5 adsorbent follows first-order reversible kinetics. The forward and backward constants for adsorption, k ₁and k ₂ have been calculated at different temperatures between 10 and 60^∘C. Form kinetic study, the values of Δ H ^* and Δ S ^* were calculated for Gd(III) and U(VI) at 25^∘C. It is found that Δ H ^* equals −14.8 kJmol⁻¹ and 7.2 kJmol⁻¹ for Gd(III) and U(VI), respectively, while Δ S ^* were found equal −95.7 Jmol⁻¹K⁻¹ and −70.5 Jmol⁻¹K⁻¹ for Gd(III) and U(VI), respectively. The study showed that the pore diffusion is the rate limiting for Gd(III) and (VI).     

Removal of lead(II) and zinc(II) ions from aqueous solutions by adsorption onto activated carbon synthesized from watermelon shell and walnut shell

Activated carbons from watermelon shell (GACW) and walnut shell (GACN) were synthesized through chemical activation with phosphoric acid 40 % w/w, as an alternative low-cost adsorbent for the removal of lead(II) and zinc(II) ions from aqueous solutions. The yield of production was 85 and 80 % for GACW and GACN respectively. To compare the differences and similarities between the two activated carbons the following tests were performed: surface and pore width with SEM, nitrogen adsorption isotherms at ?196 °C (77 K), IR spectroscopy, TGA, point of zero charge (PZC) and Boehm titration. The GACN has 10 % more surface area (789 m² g^?1 for GACN and 710 m² g^?1 for GACW) and 13 % more pore volume than GACW. Also, GACN has a better resistance to high temperatures than GACW (the loss of mass at 900 °C was 20 % for GACN, while for GACW was 31 %). The effect of the initial concentration of lead(II) and zinc(II) ions on the adsorption process was studied in a batch process mode. To quantify the adsorption of lead and zinc adsorption isotherms of both metals in aqueous solution were performed for each carbon using analytic technique of atomic absorption. The adsorption isotherm data were better fitted by Langmuir model. Experimental results suggests that one gram of GACW adsorbs more milligrams of lead(II) and zinc(II) than one gram of GACN; it is suggest that the pore distribution is a significant variable in the adsorption process because GACW present mesopores and micropores, while GACN has only micropores. Also, the surface chemistry is an important variable in the adsorption process because GACW presents a lower pH_PZC than GACN (3.05 for GACW and 4.5 for GACN) and the solution’s pH of each metal was adjusted in 4.5, for that it could be suggested that the electrostatic interactions were increased between the ion and the carbon surface.     

Biosorption of copper (II) and lead (II) from aqueous solutions by nonliving green algae Cladophora fascicularis: Equilibrium, kinetics and environmental effects

Biosorption of Cu²⁺ and Pb²⁺ by Cladop- hora fascicularis was investigated as a function of initial pH, initial heavy metal concentrations, temperature and other co-existing ions. Adsorption equilibriums were well described by Langmuir and Freundlich isotherm models. The maximum adsorption capacities were 1.61 mmol/g for Cu²⁺ and 0.96 mmol/g for Pb²⁺ at 298 K and pH 5.0. The adsorption processes were endothermic and biosorption heats calculated by the Langmuir constant b were 39.0 and 29.6 kJ/mol for Cu²⁺ and Pb²⁺, respectively. The biosorption kinetics followed the pseudo-second order model. No significant effect on the uptake of Cu²⁺ and Pb²⁺ by co-existing cations and anions was observed, except EDTA. Desorption experiments indicated that Na₂EDTA was an efficient desorbent for the recovery of Cu²⁺ and Pb²⁺ from biomass. The results showed that Cladophora fascicularis was an effective and economical biosorbent material for the removal and recovery of heavy metal ions from wastewater.     

Kinetics and Equilibrium Models for Sorption of Cu(II) onto a Novel Manganese Nano-adsorbent

The studies of kinetics and equilibrium sorption of Cu(II) were undertaken using nanoscale zerovalent manganese (nZVMn) synthesized by chemical reduction in a single pot system. nZVMn was characterized using scanning electron microscopy, energy dispersive x-ray, and surface area determined by Brunauer–Emmett–Teller. The effect of pH, contact time, adsorbent dose, agitation speed, initial Cu(II) concentrations, temperature, and ionic strength on the sorption of Cu(II) onto nZVMn were investigated in a batch system. The kinetic data followed pseudo-second-order. The mechanism was governed by pore diffusion. The equilibrium sorption data were tested by Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich, and Halsey isotherm models. The Langmuir monolayer adsorption capacity (Q_max = 181.818 mg/g) is much greater compared to other nano-adsorbents used in sorption of Cu(II). The thermodynamic parameters (ΔH⁰, ΔS⁰, ΔG⁰) revealed a feasible, spontaneous, and endothermic adsorption process. nZVMn has a great potential for effective removal of copper (II) in aqueous solution.     

Cu(II) removal enhancement from aqueous solutions using ion-imprinted membrane technique

In this study, Cu(II)-ion-imprinted membrane adsorbents were prepared via cross-linking of blended chitosan/poly(vinyl alcohol) using glutaraldehyde as cross-linker and copper ions as template. The ability of IIMs to adsorb copper ions from aqueous solutions was assessed using a batch of experiments under different conditions by changing cross-linking density (0.05 mass %, 0.1 mass %, and 0.2 mass %), template content (0.2 mass %, 0.5 mass %, and 0.9 mass %), initial analyte concentration (50 mg L^?1, 100 mg L^?1, and 150 mg L^?1), and adsorbent concentration (0.5 g L^?1, 1.0 g L^?1, and 2.0 g L^?1). The Taguchi method was used to plan a minimum number of experiments. The following optimal levels were thus determined for the four factors: cross-linking density: 0.1 mass %; template content: 0.5 mass %; initial analyte concentration: 150 mg L^?1; and adsorbent concentration: 0.3 g L^?1.     

Removal of Cd(II) and Cu(II) ions from aqueous solutions using tannin-phenolic polymer immobilized on cellulose

Tannin was crosslinked with paraformaldehyde to prepare tannin-phenolic polymer(TP), TP immobilized on cellulose (TPPC) was prepared by the cross-linking reaction of TP and cellulose with epichlorohydrin as crosslinking agent. Tannin was crosslinked prior to being immobilized on cellulose, which could increase the effective phenolic hydroxyl content in cellulose skeleton and improve the adsorption property of TPPC for metal ions. The maximum adsorption capacity of TPPC for Cd(II) and Cu(II) ions were 80.11?mg/g and 55.97?mg/g, respectively. The adsorption equilibrium data for the metal solutions fitted the Langmuir model well. The adsorption rate data fitted well to a Pseudo-second-order model. The TPPC has potential application value in the field of metal wastewater treatment.     

Characteristics of sorption of uncomplexed and complexed Pb(II) from aqueous solutions onto peat

Batch experiments aimed at the sorption of Pb(II) onto peat were performed from an aqueous solution in both the absence and presence of common complexing agents (acetate or citrate). The influence of the initial pH of the solution, metal ion concentration and contact time on the sorption efficiency of Pb(II) was examined at ambient temperature (18 ± 0.5) °C for each experiment. The results showed that the presence of acetate improved the efficiency of the sorption process, while the presence of citrate in the aqueous solution decreased the efficiency of the Pb(II) sorption onto peat. The equilibrium data fitted well with the Langmuir isotherm model and confirmed the monolayer sorption of uncomplexed and complexed Pb(II) species onto peat. The values of maximum sorption capacities (q _max) were 135.13 mg g⁻¹ for Pb(II) complexed with acetate, q > 79.36 mg g⁻¹ for uncomplexed Pb, q > 38.46 mg g⁻¹ for Pb(II) complexed with citrate. The kinetics of Pb(II) sorption onto peat, in both the absence and presence of complexing agents, indicated a pseudosecond order mechanism. Analysis of IR spectra showed that carboxylic and hydroxyl groups had an important role in the binding process of Pb(II) species onto peat.