Ion‐exchange adsorption of calcium ions from water and geothermal water with modified zeolite A

The modified zeolite A was prepared by a two‐step crystallization method to remove scale‐forming cations from water and geothermal water. The adsorption kinetics, mechanism and thermodynamics were studied. The calcium ion adsorption capacity of the modified zeolite A was 129.3 mg/g (1 mg/g = 10^?3 kg/kg) at 298 K. The adsorption rate was fitted well with pseudo‐second‐order rate model. The adsorption process was controlled by film diffusion at the calcium ion concentration less than 250 mg/L (1 mg/L = 10^?3 kg/m³), and it was controlled by intraparticle diffusion at the concentration larger than 250 mg/L. The calculated mass‐transfer coefficient ranged from 2.23 × 10^?5 to 2.80 × 10^?4cm/s (1 cm/s = 10^?2m/s). Dubinin–Astakhov isotherm model could appropriately describe the adsorption thermodynamic properties when combined with Langmuir model. The adsorption process included not only ion exchange but also complexation between calcium and hydroxyl ions. The adsorption was spontaneous and endothermal. The high adsorption capacity indicates that the modified zeolite A is a suitable adsorption material for scale removal from aqueous solution. © 2014 American Institute of Chemical Engineers AIChE J, 61: 640–654, 2015     

[Dye molecules/copper(II)/macroporous glutaraldehyde‐chitosan] microspheres complex: Surface characterization,kinetic, and thermodynamic investigations

Chitosan microspheres loaded Cu(II) were prepared using a precipitation method and heterogeneously crosslinked with glutaraldehyde. The abilities of the binary [Cu(II)/Glut‐chitosan] system for binding two acid dyes, that is, Acid blue 25 (AB25) and Calmagite (Calma) were investigated. Sorption experiments were performed using a batch process at 25°C and indicate pH dependence. Evidence for the modification of the raw chitosan polymer was provided by Fourier transform infra red spectral study, thermogravimetry, differential thermogravimetry, differential scanning calorimetry, and scanning electron microscopy analysis. Data gleaned from the thermal analyses, showed that the modification of the polymer decreases the thermal stability of the prepared materials with respect to that of the native one. The effecting factors during dye adsorption have been also studied. Thermodynamic and kinetic experiments were undertaken to assess the capacity and the rate of dyes removal on the surface of [Cu(II)/Glut‐chitosan]. Experimental data were mathematically described using various kinetic models. The pseudo second‐order equation was shown to fit the adsorption kinetics. The interpretation of the equilibrium sorption data complies well with the Freundlich adsorption model. Thermodynamic results indicate that the adsorption follows an exothermic process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A Pongamia pinnata pods based activated carbon as an efficient scavenger for adsorption of toxic Co(II): kinetic and thermodynamic study

ABSTRACT

A porous and high surface area-activated carbon based on Pongamia pinnata pods (PPP) was synthesized using a chemical method. The synthesized material was characterized using FTIR, XRD, BET, SEM, EDX, XPS and TGA. Plausible adsorption mechanism of Co(II) on PPPAC was evaluated systematically. The effect of various contributing parameters were investigated through batch adsorption experiments. Results reveal that the equilibrium was attained within 360 min having 0.35 g PPPAC amount at pH 6 and the maximum equilibrium capacity was observed 190.30 mg/g. Kinetically adsorption of Co(II) was best described by pseudo-second-order-model. The equilibrium data well suited with the Langmuir isotherm model and thermodynamic parameters indicate that the process was spontaneous and endothermic in nature.     

Surface modification of silicone rubber by ion beam assisted deposition (IBAD) for improved biocompatibility

We studied the preparation of antimicrobial silicone rubbers of improved interfacial strength, which could be formed with the ion beam assisted deposition (IBAD) technique for coating metallic or inorganic materials (silver (Ag), Copper (Cu), and Hydroxyapatite(HAp)/TiO₂) on the silicone surface. Those coating materials provide high product safety as well as outstanding antimicrobial activity. The deposition methodology is composed of pre‐etching with oxygen gas, vaporizing the coating materials, and post‐treatment with Ar ion. With the evaporation of the coating materials, the Ar beam was focused on the substrate to assist deposition. It was found out that the ion assisting depositions in the IBAD process give a prominent enhancement in adhesion between silicone rubbers and coatings of Ag and Cu. The HAp/TiO₂ coating layer was easily dissolved in aqueous saline solution. All deposited layers display high antimicrobial activities against Staphlococcus aureus (ATCC 6538) and Escherichia coil (ATCC 25,922), showing 99.9% reduction of bacteria, respectively. In a cytotoxicity test, the Ag and HAp/TiO₂ coated silicone shows a decrease of cytotoxicity, while the Cu coating leads to a slight increase of cytotoxicity. The result on the surface modifications of silicone rubber will be employed in further study for applications of medical or rehabilitation devices. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1095–1101, 2005     

Kinetic,isotherm, and thermodynamic studies of Cr(VI) removal from aqueous solution using mesoporous silica materials prepared by fly ash

A series of mesoporous silica materials (FMD, FMT, and FMC were synthesized with DTAB, TTAB, and CTAB as template, respectively) have been prepared using fly ash as a silica resource. The as-synthesized materials were characterized by BET, XRF, FTIR, and XPS. The results confirmed the mesoporous structure and nitrogen content to act as potential adsorbents. The adsorption properties of these materials were also investigated by batch adsorption experiments. The FMC exhibited the highest effective removal of Cr(VI) (99%). The Cr(VI) adsorption process over FMC follows the pseudo-second-order kinetic and Langmuir model. Thermodynamic studies revealed that the Cr(VI) adsorption by FMC was spontaneous and endothermic. The study of the adsorption mechanism showed that the removal of Cr (VI) by FMC is through electrostatic attraction and chemical reduction. The coexisting ions experiment showed that FMC had high selectivity for Cr(VI). After three regeneration cycles, the Cr(VI) removal rate of FMC adsorbent still remained about 80%. Thus, this inexpensive adsorbent (FMC) is suitable for removing Cr(VI) from discharged industrial water.     

Ion-imprinted polyvinylimidazole-silica hybrid copolymer for selective extraction of Pb(II): Characterization and metal adsorption kinetic and thermodynamic studies

The current paper presents a synthesis of a novel ion-imprinted hybrid copolymer (IIHC) [poly(1-vinylimidazole)-co-(3-(trimethoxysilyl)propyl methacrylate) and its application to selective adsorption of Pb²⁺ ions. The hybrid copolymer was prepared by coupling free radical addition and sol-gel processing, using tetraethoxysilane (TEOS) as cross-linker. Thermogravimetry (TG), FT-IR, X-ray diffraction, specific surface area (BET) and scanning electron microscopy (SEM) were used to characterize the copolymers. The equilibrium data obtained were fitted very well to the non-linear Langmuir-Freundlich isotherm model, as compared to other models, and the maximum adsorption uptake was found to be 7.6 mg g⁻¹. The thermodynamic parameters, including Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) of the adsorption process, were found to be −16.23 kJ mol⁻¹, −10.37 kmol⁻¹ and −19.42 J K⁻¹ mol⁻¹, respectively. These results demonstrate that the adsorption of Pb²⁺ onto the hybrid copolymer takes place by a spontaneous and exothermic process with further decrease in the degree of freedom without disordering at the solid-solution interface due to the negative ΔS° value. Furthermore, the pseudo-first-order and pseudo-second-order models were used to describe the kinetic data. The experimental data were fitted well to the pseudo-first-order kinetics. Under competitive adsorption conditions, the ion-imprinted hybrid copolymer was 8.8, 64.9 and 16 times more selective when compared to the blank copolymer (NIC - non-imprinted copolymer) for Pb²⁺/Cu²⁺, Pb²⁺/Cd²⁺, and Pb²⁺/Zn²⁺ systems.     

Equilibrium,kinetic, and thermodynamic studies of the Ca2+ and Mg2+ ions removal from water by Duolite C206A

The uptake of Ca²⁺ and Mg²⁺ ions from synthetic aqueous solutions by Duolite C206A was studied in static-batch mode. Results revealed that there is no need of pH adjustment. The equilibrium is reached after 30 min with 0.5 g of resin at 25°C. Equilibrium data were well fitted by Langmuir isotherm model. Maximum uptake capacities Q_max were about 23.04 mg Mg²⁺/g and 64.10 mg Ca²⁺/g. The pseudo-second-order model was found as the best to explain the ions exchange kinetics effectively. The uptake of Ca²⁺ and Mg²⁺ ions by Duolite C206A is exothermic and the process is spontaneous.     

Biosorption of Pb(II) using Gundelia tournefortii: Kinetics,equilibrium, and thermodynamics

In this paper, the feasibility of Gundelia tournefortii was studied as a novel, high-capacity biosorbent for removing lead ions from synthetic wastewater in a batch system. The effects of various parameters such as temperature, initial concentration, initial pH, biosorbent dosage, and contact time were investigated. Based on batch results, the optimum operating conditions were found to be pH 5, biosorbent dosage of 25 mg, and temperature of 20°C in the range of lead initial concentrations from 5 to 100 mg/L. The equilibrium contact time was 60 min. The biosorption mechanism can be well described by the Langmuir isotherm with a monolayer maximum adsorption capacity of 144.928 (mg/g) at 20°C and a pseudo-second-order kinetic model. Thermodynamic studies proved that the sorption process was physical, spontaneous, feasible, random, and exothermic. In the second step, the ability of artificial neural network (ANN) to predict the adsorption capacity of Gundelia tournefortii for the removal of Pb(II) from aqueous solution was examined. The model was developed using a three-layer feed-forward back-propagation (BP) network with 5, 12, and 1 neurons in the first, second, and third layers, respectively. The Levenberg–Marquardt BP training algorithm (LMA) was found to be the best BP algorithm with a minimum mean squared error of 0.000867 and a minimum relative squared error of 0.032771. The comparison between the results of ANN and experimental data showed that ANN has a superior performance (R²= of 0.998) in the prediction of the Pb(II) removal process.     

Polymer‐grafted banana (Musa paradisiaca) stalk as an adsorbent for the removal of lead(II) and cadmium(II) ions from aqueous solutions: kinetic and equilibrium studies

This study examined the effectiveness of a new adsorbent prepared from banana (Musa paradisiaca) stalk, one of the abundantly available lignocellulosic agrowastes, in removing Pb(II) and Cd(II) ions from aqueous solutions. The adsorbent (PGBS‐COOH) having a carboxylate functional group at its chain end was synthesized by graft copolymerization of acrylamide on to banana stalk, followed by functionalization. Batch adsorption experiments were carried out as a function of solution pH, ionic strength, contact time, metal concentration, adsorbent dose and temperature. A pH range of 5.5–8.0 was found to be effective for the maximum removal for both Pb(II) and Cd(II). Metal uptake was found to decrease with increase in ionic strength due to the expansion of the diffuse double layer and, more importantly, the formation of some chloro complexes (since NaCl was used in the adjustment of ionic strength), which do not appear to be adsorbed to the same extent as cations [M²⁺ and M(OH)⁺]. The kinetic studies showed that an equilibrium time of 3 h was needed for the adsorption of Pb(II) and Cd(II) on PGBS‐COOH and adsorption processes followed a pseudo‐second‐order equation. The Langmuir isotherm model fitted the experimental equilibrium data well. The maximum sorption capacity for Pb(II) and Cd(II) ions was 185.34 and 65.88 mg g^?1, respectively, at 30 °C. The thermodynamic parameters such as changes in free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were derived to predict the nature of adsorption. The isosteric heat of adsorption was found to be independent of surface coverage. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC‐50, for comparison. Synthetic wastewater samples were treated with the adsorbent to demonstrate its efficiency in removing Pb(II) and Cd(II) ions from industrial wastewaters. Acid regeneration was tried for several cycles with a view to recovering the sorbed metal ions and also restoring the sorbent to its original state. Copyright © 2005 Society of Chemical Industry     

Equilibrium modeling,kinetic and thermodynamic studies on the adsorption of Cr(VI) using activated carbon derived from matured tea leaves

A new porous carbon with high surface area of 1,313.41 m² g^?1 with pore volume 1.359 cm³ g^?1 has been synthesized from matured tea leaves by chemical activation method using phosphoric acid. The carbon was found to be highly efficient for removal of Cr(VI) from aqueous solution. The effects of various parameters such as contact time, initial metal ion concentration, pH, temperature and amount of adsorbent on the extent of adsorption were studied. Langmuir, Freundlich and Temkin adsorption models were used to interpret the experimental data. The adsorption data were best fitted with Langmuir isotherm model. The adsorption capacity of Cr(VI) onto the activated carbon calculated from Langmuir isotherm was found to be 30.8 mg g^?1 at pH 4.8 and temperature 303 K. The adsorption capacity increases from 25.36 to 32.04 mg g^?1 with an increase in temperature from 303 to 323 K at initial Cr(VI) concentration of 60 mg L^?1. The adsorption process followed a pseudo second order kinetic model. Thermodynamic parameters ΔH⁰ (28.6 KJ mol^?1), ΔG⁰ at three different temperatures [(?0.145, ?1.09, ?2.04) KJ mol^?1] and ΔS⁰ (94.87 J mol^?1 K^?1) were calculated. These values confirm the adsorption process to be endothermic and spontaneous in nature.     

Characterisation and adsorption properties of oxalate-loaded hematite composite for Cd(II) and Pb(II) adsorption: Equilibrium models,thermodynamic and kinetic studies

In this study, different reagents have been examined to improve the adsorption ability of hematite for the removal of Cd(II) and Pb(II) ions from aqueous solution. The best adsorption result has been obtained using oxalate-loaded hematite. The equilibrium isotherm studies show the best result was attained in the Langmuir model for Pb(II) and Cd(II) ions. Therefore, homogeneous adsorption is dominated, which was emphasised by three-parameter-isotherm models. The experimental data fit well with the pseudo-second-order kinetics. The Pb(II) adsorption was endothermic and spontaneous, but the Cd(II) adsorption was exothermic and unspontaneous.     

Conversion of soybean oil into ion exchange resins: Removal of copper (II), nickel (II), and cobalt (II) ions from dilute aqueous solution using carboxylate‐containing resin

An ion‐exchange resin containing carboxylic acid groups was prepared by reaction of epoxidized soybean oil with triethylene tetramine, followed by hydrolysis of glycerides by using sodium hydroxide solution. The cation exchange capacity of the resins was determined to be 3.50 mequiv/g. The adsorption capacity for Cu²⁺, Ni²⁺, and Co²⁺ on the obtained resin at pH 5.0 was found to be 192, 96, and 78 mg/g, respectively. Effect of pH on the adsorption capacity for copper (II), nickel (II), and cobalt (II) ions were also studied. Cu²⁺, Ni²⁺, and Co²⁺ were adsorbed at a pH above 3. These metal ions adsorbed on the resin are easily eluted by using 1N HCl solution. The selectivity of the resin for Cu²⁺ from mixtures containing Cu²⁺/Co²⁺/Ni²⁺ ions in the presence of sodium chloride was also investigated © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2386–2396, 2002     

Adsorption isotherm and kinetic modeling of a novel procedure for physical modification of silica gel using aqueous solutions of 4,4′-(1,2-ethanediyldinitrilo)bis-(2-pentanone) for preconcentration of Ni(II) ion

ABSTRACT

Aqueous solutions of 4,4′-(1,2-ethanediyldinitrilo)bis-(2-pentanone) (EDDBP) have been used in a novel green procedure for the physical modification of silica gel (SG) for solid-phase extraction and preconcentration of Ni(II) ion. Optimization experiments were carried out at 301 ± 1 K by batch technique. The EDDBP-modified SG was characterized using X-ray Diffraction Spectroscopy (XRD) and Brunaeur-Emmett-Teller (BET) determinations. The adsorption isotherm and kinetic models indicated a physisorption process. The modified SG showed moderate to high adsorption capacity values for Ni(II) ion (~98% removal efficiency) at pH 8. A sorption mechanism for Ni(II) chelation with EDDBP-modified-SG was proposed. These results suggest the procedure has advantages.     

Application of kinetic,isotherm and thermodynamic models for the adsorption of Co(II) ions on polyaniline/polypyrrole copolymer nanofibers from aqueous solution

The aim of this research is to investigate sorption characteristics of polyaniline/polypyrrole copolymer nanofibers (PANI/PPy copolymer nanofibers) for the removal of Co(II) ions from aqueous solution. The adsorbent is characterized using FE-SEM, TEM, FTIR, TGA, DSC and BET surface area. The sorption of Co(II) ions by batch method is applied and the optimum conditions are investigated. In optimum condition, removal efficiency was 99.68% for 100 mg L⁻¹ Co(II) solution. It is found that temperature has a positive effect on the removal efficiency. It can be concluded that PANI/PPy copolymer nanofibers are potentially able to removal of Co(II) ions from aqueous solutions.     

Heterocyclic modification of chitosan for the adsorption of Cu (II) and Cr (VI) ions

A heterocyclic modification of chitosan has been attempted for development of an effective adsorbent material for removal of metal ions. The modified polymer was characterized using infrared (IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD) techniques. The adsorption capacity exhibited for Cu (II) and Cr (VI) were 83.75 and 85.0 mgg^?1, respectively, which is a significant improvement over chitosan. The adsorption on the modified polymer was a second-order kinetic process and followed Langmuir isotherm model. The thermodynamic analysis indicated exothermic and spontaneous nature of adsorption. About 80% of the adsorbed metal ions were desorbed in appropriate stripping solutions indicating reusability.     

Adsorption of rhodium(III) ions onto poly(1,8-diaminonaphthalene) chelating polymer: Equilibrium,kinetic and thermodynamic study

In the present work, poly(1,8-diaminonaphthalene) (poly(1,8-DAN)) was synthesized by the reaction of 1,8-diaminonaphthalene (1,8-DAN) with ammonium persulfate (APS) and then the equilibrium, kinetics and thermodynamics of rhodium(III) adsorption onto poly(1,8-DAN) were studied. Poly(1,8-DAN), Rh(III)-poly(1,8-DAN) and Rh(III)-1,8-DAN complex were characterized by UV–vis. and FTIR spectroscopy, thermal analysis, potentiometric titration and electrical conductivity. In the adsorption studies, the effects of acidity, the temperature and the concentration of rhodium(III) were examined. It was found that poly(1,8-DAN) has Rh(III) adsorption capacity (q_m) of 11.11 mg/g polymer. The adsorption data fitted better to the Freundlich isotherm then the Langmuir isotherm, and the kinetics of the adsorption fitted to pseudo second order kinetic model. The ΔG° values were calculated as ?7.33 at 20 and ?11.31 kJ/mol at 60 °C. The enthalpy (ΔH°), entropy (ΔS°) and the activation energy (E_a) of the adsorption were found as 21.335 kJ/mol, 97.057 J/mol K and 70.210 kJ/mol, respectively. It was predicted that the adsorption of Rh(III) onto poly(1,8-DAN) was an endothermic chemical adsorption process governed by both ionic interaction and chelating mechanisms. It was also observed that the adsorption of Rh(III) lowered the electrical conductivity of the pol(1,8-DAN).