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.     

Adsorption of cadmium ions from aqueous solutions using nano-montmorillonite: kinetics,isotherm and mechanism evaluations

With increasing industrial development, heavy metal pollution, e.g., cadmium (Cd) pollution, is increasingly serious in soil and water environments. This study investigated the sorption performance of nano-montmorillonite (NMMT) for Cd ions. Adsorption experiments were carried out to examine the effects of the initial metal ion concentration (22.4–224 mg/L), pH (2.5–7.5), contact time (2–180 min) and temperature (15–40 °C). A simulated acid rain solution was prepared to study the desorption of Cd adsorbed on NMMT. After the adsorption or desorption process, the supernatant was analyzed using a flame atomic absorption spectrometry method. The Cd removal rate increased as the pH and contact time increased but decreased as the initial metal ion concentration increased. The maximum adsorption capacity was estimated to be 17.61 mg/g at a Cd²⁺ concentration of 22.4 mg/L. The sorption process can be described by both the Langmuir and Freundlich models, and the kinetic studies revealed that the pseudo-second-order model fit the experimental data. The Cd desorption rate when exposed to simulated acid rain was less than 1%. NMMT possesses a good adsorption capacity for Cd ions. Additionally, ion exchange was the main adsorption mechanism, but some precipitation or surface adsorption also occurred.     

Adsorption kinetics and isotherm parameters of naphthalene onto natural- and chemically modified bentonite from aqueous solutions

Polycyclic aromatic hydrocarbons (PAHs) have widely been studied and a special concern because of their mutagenic and carcinogenic activities. In this study, natural- and chemically modified-bentonite were characterized by means of N₂ adsorption method, XRD, SEM, FT-IR, elemental and thermal analysis and zeta potential techniques and their adsorption behavior were then investigated toward naphthalene, which is the first member of the PAHs. The effects of various experimental parameters such as pH, contact time and temperature on adsorption were tested in the experiments. The optimum pH values for naphthalene adsorption onto natural bentonite (NB) and hexadecyltrimethylammonium bromide modified bentonite (HB) were found to be as 4.00 and 5.97, respectively. The equilibrium contact time was 60 min for both of the adsorbent. A comparison of the linear and nonlinear method of three widely used kinetic models, which are Lagergren-first order, the pseudo-second-order and Elovich kinetics, and the most popular isotherms, which are Langmuir and Freundlich, were examined to the experimental data of the adsorption of naphthalene onto NB and HB. The kinetic results indicated that the pseudo-second-order kinetic model with high correlation coefficients was more suitable than the other kinetic models e.g. Lagergren first-order and Elovich. All results showed that the modified bentonite can be used as an adsorbent to remove PAHs from aqueous solutions by using adsorption method due to its effectiveness, simplicity and low-cost than the other conventional methods.     

Adsorption of humic acid from aqueous solutions on crosslinked chitosan-epichlorohydrin beads: kinetics and isotherm studies

The adsorption of humic acid on crosslinked chitosan-epichlorohydrin (chitosan-ECH) beads was investigated. Chitosan-ECH beads were characterized by Fourier transform infrared spectroscopy (FTIR), surface area and pore size analyses, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out and optimum humic acid adsorption on chitosan-ECH beads occurred at pH 6.0, agitation rate of 300 rpm and contact time of 50 min. Adsorption equilibrium isotherms were analyzed by Langmuir and Freundlich models. Freundlich model was found to show the best fit for experimental data while the maximum adsorption capacity determined from Langmuir model was 44.84 mg g(-1). The adsorption of humic acid on chitosan-ECH beads was best described with pseudo-first-order kinetic model. For desorption study, more than 60% of humic acid could be desorbed from the adsorbent using 1.0M HCl for 180 min.     

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.     

Adsorption of metal ions onto Moroccan stevensite: kinetic and isotherm studies

The aim of this paper is to study the adsorption of the heavy metals (Cd(II), Cu(II), Mn(II), Pb(II), and Zn(II)) from aqueous solutions by a natural Moroccan stevensite called locally rhassoul. We carried out, first, a mineralogical and physicochemical characterization of stevensite. The surface area is 134 m2/g and the cation exchange capacity (CEC) is 76.5 meq/100 g. The chemical formula of stevensite is Si3.78Al0.22Mg2.92Fe0.09Na0.08K0.08O10(OH)2.4H2O. Adsorption tests of Cd(II), Cu(II), Mn(II), Pb(II), and Zn(II) in batch reactors were carried out at ambient temperature and at constant pH. Two simplified models including pseudo-first-order and pseudo-second- order were used to test the adsorption kinetics. The equilibrium time and adsorption rate of adsorption were determined. The increasing order of the adsorption rates follows the sequence Mn(II) > Pb(II) > Zn(II) > Cu(II) > Cd(II). The Dubinin-Radushkevich (D-R), Langmuir, and Redlich-Peterson (R-P) models were adopted to describe the adsorption isotherms. The maximal adsorption capacities at pH 4.0 determined from the D-R and Langmuir models vary in the following order: Cu(II) > Mn(II) > Cd(II) > Zn(II) > Pb(II). The equilibrium data fitted well with the three-parameter Redlich-Peterson model. The values of mean energy of adsorption show mainly an ion-exchange mechanism. Also, the influence of solution pH on the adsorption onto stevensite was studied in the pH range 1.5-7.0.     

Adsorption dynamics and equilibrium studies of Zn (II) onto chitosan

Batch equilibration studies are conducted to determine the nature of adsorption of zinc (II) over chitosan. The factors affecting the adsorption process like particle size, contact time, dosage, pH, effects of chloride and nitrate are identified. The influence of temperature and co-ions on the adsorption process is verified. The fraction of adsorption,Y _t and the intraparticle diffusion rate constant,k _p are calculated at different environments and the results are discussed. The nature of adsorption of the zinc (II)-chitosan system is explained using Freundlich, Langmuir isotherms and thermodynamic parameters     

Equilibrium and kinetics studies on adsorption of Cu(II) from aqueous solutions onto a graft copolymer of cross-linked starch/acrylonitrile (CLSAGCP)

A synthetic graft copolymer of cross-linked starch/acrylonitrile was used as an adsorbent for the removal of Cu(II) ions from an aqueous solution of copper nitrate hexahydrate Cu(NO₃)₂ · 6H₂O at different temperatures and fixed pH. The amount adsorbed increased with increasing concentration of Cu(II) ions and decreasing temperature. The length of time taken to reach equilibrium of the adsorption of Cu(II) ions was the same at all temperatures tested. Kinetics studies showed that the adsorption process obeyed first-order reversible kinetics and the adsorption isotherms followed the Freundlich model. Furthermore, the thermodynamic parameters, i.e. standard free energy (ΔG^∘), standard enthalpy (ΔH^∘), and standard entropy (ΔS^∘), of the adsorption process were calculated and the results are discussed in detail.     

Adsorption of copper(II) ions from aqueous solutions on alumina industrial wastes

Equilibrium adsorption of copper(II) ions on red mud (alumina industrial wastes) modified by various methods was studied. The effect exerted by the nature the modifier (NaHSO₄, NaCl + HCl, and H₂SO₄) on the sorption activity of red mud was determined.     

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.     

Adsorption of Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II) from aqueous solutions on a 2-mercaptobenzimidazole-modified silica gel

The chemically modified silica, obtained by reacting 2-mercaptobenz-imidazole with 3-chloropropyl silica gel, was used to adsorb Cu(II), Zn(II), Cd(II) and Pb(II) from aqueous solutions at various pH. Between pH 3–5, the order of selectivity was Hg(II) > Cd(II) Cu(II) Zn(II) Pb(II). Under batch conditions retentions of 100% were achieved for all metals except for Pb(II) where 93% was attained. Under column conditions recoveries of 100% were obtained for all metals.     

Adsorption of strontium (II) ions from aqueous solution onto bottom ash of expired drug incineration

Journal of Radioanalytical and Nuclear Chemistry - Bottom Ash of Expired Drug Incineration (BAEDI) is used in this study for the removal of Sr(II). In the kinetic study, 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.     

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.     

Adsorption studies of cesium on potassium copper nickel hexacyanoferrate(II) from aqueous solutions

Adsorption of cesium from aqueous solutions on potassium copper nickel hexacyanoferrate(II) (KCNF) has been investigated in batch experiments and optimized as a function of concentration of acids, salts and adsorbate using a radiotracer technique. The results are presented in terms of distribution coefficient, K_d (ml·g^–1). The uptake of cesium obeys a Freundlich adsorption isotherm over the concentration range of 3.7 to 37 mmol·l^–1 with b values of 0.77, 0.68 and 0.56 at temperatures of 293, 313, 333 K, respectively. The Langmuir adsorption isotherm is followed in the concentration range of 15 to 75 mmol·l^–1 in the same temperature range. The values of limiting adsorption concentration (C_m) have been found to be 2.58, 2.44 and 2.32 mmol·g^–1. The heat of adsorption was calculated as 26.43 kJ·mol^–1. The influence of a number of anions and cations on cesium retention has also been studied. Column experiments have been performed and breakthrough have been obtained under different operating conditions. The low cesium capacity of 1.1 mmol·g^–1 has been obtained under dynamic conditions as compared to batch experiments. Desorption of cesium from the column has been achieved (45.4%) by nitric acid solution of 8M concentration at a flow rate of 0.5 ml·min^–1.     

Adsorption behavior of Pd(II) ions from aqueous solution onto pyromellitic acid modified-UiO-66-NH2

A new adsorbent was successfully fabricated by chemically linking pyromellitic acid onto a zirconium-based metal-organic framework composite for selective adsorption of Pd(II) from an aqueous solution. The adsorbent was characterized by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller equation and scanning electron microscope. The adsorption capacity, selectivity and repeatability of the adsorbent were tested by batch experiments. The optimum pH was 2.0, and the maximum adsorption capacity at room temperature was 226.1 mg/g. In the kinetic experiments, the adsorption process achieved equilibrium within 5 h and generally conformed to the quasi-second kinetics and Freundlich isotherm model. The N-H and OH groups on the adsorbent interacted with Pd(II) by electrostatic and coordination action. The adsorbent maintained excellent adsorption capacity after at least 5 cycles. At the same time, the selectivity of the adsorbent in aqueous solution is excellent from interfering ions. Therefore, the new adsorbent will have an obvious application prospect on the recovery of palladium.     

Adsorption of Ni(II), Cu(II) and Cd(II) from aqueous solutions by amino modified nanostructured microfibrillated cellulose

The aim of the present study was to investigate the adsorption properties of aminopropyltriethoxysilane (APS) modified microfibrillated cellulose (MFC) in aqueous solutions containing Ni(II), Cu(II) and Cd(II) ions. The modified adsorbents were characterized using elemental analysis, Fourier transform infrared spectroscopy, SEM and zeta potential analysis. The adsorption and regeneration studies were conducted in batch mode using various different pH values and contact times. The maximum removal capacities of the APS/MFC adsorbent for Ni(II), Cu(II), and Cd(II) ions were 2.734, 3.150 and 4.195 mmol/g, respectively. The Langmuir, Sips and Dubinin-Radushkevich models were representative to simulate adsorption isotherms. The adsorption kinetics of Ni(II) Cu(II), and Cd(II) adsorption by APS/MFC data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that the pseudo-second-order kinetic equation and intra-particle diffusion model were adequate to describe the adsorption kinetics.     

Biosorption of Cr(VI) ions from aqueous solutions: kinetics, equilibrium, thermodynamics and desorption studies

Cr(VI) is a major water pollutant from industrial effluent whose concentration is to be reduced within the permissible limit. Present study reports a systematic evaluation of six different natural adsorbents for the removal of Cr(VI) from aqueous solutions in batch process. The adsorption kinetic data were best described by pseudo-second order model. The values of mass transfer coefficient for Cr(VI) adsorption indicated that the velocity of the adsorbate transport from the bulk to the solid phase was quite fast. The effective diffusivity of Cr(VI) removal for all the adsorbents were of the order of 10(-10) m(2)/s which suggested chemisorption of the process. The adsorption process was jointly controlled by film diffusion and intraparticle diffusion. Maximum monolayer adsorption capacities onto the natural adsorbents used were comparable to the other natural adsorbents used by other researchers. The thermodynamic studies and sorption energy calculation using Dubinin-Radushkevich isotherm model indicated that the adsorption processes were endothermic and chemical in nature. FT-IR studies were carried out to understand the type of functional groups responsible for Cr(VI) binding process. Desorption study was carried out with different concentration of NaOH solutions. Application study was carried out using electroplating industrial wastewater.     

Effect of pH on Competitive Adsorption of Cu(II), Ni(II), and Zn(II) from Water onto Chitosan Beads

The amounts of adsorption of Cu²⁺, Ni²⁺, and Zn²⁺ from single, binary, and tertiary nitrate solutions onto glutaraldehyde cross-linked chitosan beads were measured. The beads had an average particle size and pore volume of 2 mm and 0.06 cm³/g, respectively, and had a BET surface area of 60 m²/g. All experiments were performed at 298 K as a function of initial pH (2.0–5.0), total metal concentration (0.77–17.0 mol/m³), and molar concentration ratio (0.25–4) in the aqueous phase. It was shown that the amount of metal adsorption generally increased with increasing solution pH. Competitive adsorption was significant in binary and tertiary systems when Cu²⁺ was present. The selectivity factor reached maximum in an equilibrium pH range of 5.1–5.3 and 4.5–4.9 for the Cu-Ni and Cu-Zn binary systems, respectively. This adsorbent provided a possibility for selective separation of Cu²⁺ from such multi-component solutions.     

Adsorption of heavy-metal ions from aqueous solution onto chitosan-modified polyethylene terephthalate (PET)

Research on Chemical Intermediates - A novel chitosan-modified polyethylene terephthalate (PET) composite (CCP) adsorbent was specifically fabricated using a dip-padding method for removal of toxic...