The adsorption of Cu(II) ion from aqueous solution upon acrylic acid grafted poly(ethylene terephthalate) fibers

This study is concerned with the investigation of the adsorption properties of acrylic acid grafted poly(ethylene terephthalate) fibers by the use of Cu(II) ions in aqueous solutions. Influence of pH, graft yield, contact time, concentration of the ion, and reaction temperature on the amount of ion adsorbed upon reactive fiber were investigated. The time in which the adsorption reached to the equilibrium value was determined as 1 h. The adsorption isotherm of Cu(II) ion was found to be a Langmuir type and the heat of adsorption was calculated as ?10.1 kJ mol^?1. It was observed that the adsorbed Cu(II) ion upon acrylic acid grafted poly(ethylene terephthalate) fibers could be recovered in acidic media. The fiber could also readsorb Cu(II) ions without losing its activity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1216–1220, 2003     

Treatment of industrial glycerol from biodiesel production by adsorption operation: kinetics and thermodynamics analyses

Abstract

Equilibrium, thermodynamic, and kinetic analyses of the pigments adsorption of the industrial glycerol onto activated charcoal were performed. As the pigments concentration was not known, then, a relative adsorption capacity was defined using absorbance values measured in a spectrophotometer at a wavelength of 265?nm. Kinetic study showed that about 60?s were needed to reach equilibrium conditions. Relative adsorption capacity reached 8?g^?1 for 1% of adsorbent amount (w/w). Adsorption enthalpy was of –17.63?kJ mol^?1, while for isosteric heat values were obtained between –7.39 and –18.46?kJ mol^?1. The mathematical methodology used for the parameters determinations proved to be robust and able to express the relationships of kinetics, equilibrium and thermodynamics. Enthalpy values obtained by Van't Hoff method was confirmed by isosteric heat calculation, evidencing that this methodology can be used for systems whose compositions are unknown, but detectable by indirect form.     

Adsorption of BTX compounds from aqueous solutions by water-insoluble starch

The removal of benzene, toluene and p-xylene (BTX) compounds from aqueous solutions with highly crosslinked cationic starch containing tertiary amine groups was investigated. The adsorption process has found to be initial pH- and initial concentration-dependent, endothermic, and follows the Langmuir isothermal adsorption. The heats of adsorption (ΔH) at initial pH = 4 of benzene, toluene and p-xylene compounds are 29.45 kJ mol^?1, 34.41 kJ mol^?1, and 35.58 kJ mol^?1, respectively, those at initial pH = 10 are 30.17 kJ mol^?1, 35.56 kJ mol^?1, and 39.39 kJ mol^?1, respectively. The order of the amount of adsorbed BTX compounds on the adsorbent is benzene > toluene > p-xylene.     

Adsorptive removal of anionic and non‐ionic surfactants from aqueous phase using Posidonia oceanica (L.) marine biomass

BACKGROUND: In this study, the capability of low‐cost, renewable and abundant marine biomass Posidonia oceanica (L.) for adsorptive removal of anionic and non‐ionic surfactants from aqueous solutions have been carried out in batch mode. Several experimental key parameters were investigated including exposure time, pH, temperature and initial surfactant concentration. RESULTS: It was found that the highest surfactant adsorption capacities reached at 30 °C were determined as 2.77 mg g^?1 for anionic NaDBS and as 1.81 mg g^?1 for non‐ionic TX‐100, both at pH 2. The biosorption process was revealed as a thermo‐dependent phenomenon. Equilibrium data were well described by the Langmuir isotherm model, suggesting therefore a homogeneous sorption surface with active sites of similar affinities. The thermodynamic constants of the adsorption process (i.e. ΔG°, ΔH° and ΔS°) were respectively evaluated as ? 8.28 kJ mol^?1, 48.07 kJ mol^?1 and ? 42.38 J mol^?1 K^?1 for NaDBS and ? 9.67 kJ mol^?1, 95.13 kJ mol^?1 and ? 174.09 J mol^?1 K^?1 for TX‐100. CONCLUSION: Based on this research, valorization of highly available Posidonia oceanica biomass, as biological adsorbent to remove anionic and non‐ionic surfactants, seems to be a promising technique, since the sorption systems studied were found to be favourable, endothermic and spontaneous. Copyright © 2007 Society of Chemical Industry     

Effect of temperature on the removal of lead(II) by adsorption on China clay and wollastonite

The removal of Pb(II) from aqueous solution by adsorption on china clay and wollastonite is an attractive process. The amount of Pb(II) removed by adsorption is highly dependent on the temperature of the adsorbate solution and favours low temperature. The equilibrium times were noted, i.e. 90 min for china clay and 120 min for wollastonite. The various rate parameters of the adsorption process have been determined at different temperatures. The activation energies were determined and found to be ?5.345 kJ mol^?1 and ?8.730 kJ mol^?1 for Pb(II)-china clay and Pb(II)-wollastonite systems, respectively. The adsorption isotherm was measured experimentally at various temperatures. The negative values of enthalpy change (ΔH = ?77.95 kJ mol^?1 and ?16.40 kJ mol^?1 for china clay and wollastonite, respectively) indicate the exothermic nature of the adsorption processes for both systems. The isosteric heats of the adsorption process have been determined at various surface coverages of the adsorbents used. The various thermodynamic parameters have been calculated to elucidate the mechanism involved in the adsorption process.     

Polyelectrolyte CASA hydrogels for uptake of uranyl ions from aqueous solutions

In this study, uranyl ion adsorption from aqueous solutions has been investigated by chemically crosslinked acrylamide/sodium acrylate (CASA) hydrogels. Adsorption studies were investigated by the spectroscopic method. CASA hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), sodium acrylate (SA), and water by free radical polymerization in aqueous solution, using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA). Uranyl ion adsorption from aqueous solutions was studied by the batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of adsorbent on the uranyl ion adsorption were examined. In experiments of sorption, L‐type sorption in the Giles classification system was found. Some binding parameters, such as initial binding constant (K_i), equilibrium constant (K), monolayer coverage (n), site‐size (u), and maximum fractional occupancy (Ô) for the CASA hydrogel–uranyl ion binding system, were calculated using the Langmuir linearization method. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 4.44 × 10^?4–14.86 × 10^?4 mol uranyl ion per gram for CASA hydrogels. Adsorption of uranyl ion (percentage) was changed within a range of 12.86–46.71%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 200–204, 2007     

Polymer‐immobilized N,N′‐bis(acetylacetone)ethylenediamine cobalt(II) Schiff base complex and its catalytic activity in comparison with that of its homogenized analogue

For the preparation of a heterogenized N,N′‐bis(acetylacetone)ethylenediamine cobalt(II) Schiff base complex, first crosslinked polymer beads were prepared by the suspension copolymerization of styrene (48.97 mmol, 5.1 g), allyl chloride (48.97 mmol, 3.746 g), and divinyl benzene (DVB; 1.75 mmol, 0.228 g) in the presence of azobisisobutyronitrile (0.9 × 10^?3 mmol, 0.15 g) as an initiator at 23 ± 0.1°C under an inert atmosphere. The copolymerization of styrene, allyl chloride in the presence of gelatin (0.75 g), bentonite (2.0 g), and boric acid (2.5 g) produced beads of different crosslinked densities corresponding to the concentration of DVB in the reaction mixture. The amount of allyl chloride in the prepared beads varied from 5.40 to 7.40 mmol g^?1 of beads with the amount of DVB varying from 2.0 to 0.8 mmol in the reaction mixture. A quadridentate Schiff base (acen) was prepared with ethylenediamine (5.0 mmol, 0.3 g) and acetylacetone (10.0 mmol, 1.0 g), and it was used to obtain a homogenized and heterogenized Co(II)(acen)₂ complex. The extent and arrangement of the Schiff base (acen) in the crosslinked beads depended on the availability of DVB in the reaction mixture. The amount of DVB in the reaction mixture influenced the extent of cobalt(II) ion loading, the degree of swelling, the porosity, and the pore size in the prepared beads. The beads (type IV) prepared with 1.75 mmol (0.228 g) of DVB in the reaction mixture showed a degree of swelling of 9.65% and efficiencies of loading and complexation for cobalt(II) ions of 49.4 and 85%, respectively, in comparison with beads obtained at other concentrations of DVB in the reaction mixture. The structure of free and polymer‐supported Co(II)(acen)₂ complexes was verified with IR, UV, and magnetic measurements, which suggested a square planar geometry for the complexes under both conditions. The catalytic activities of the homogenized and heterogenized Co(II)(acen)₂ complexes were compared by the evaluation of the rate constant (k) for the decomposition of hydrogen peroxide. The heterogenized Co(II)(acen)₂ complex showed a high catalytic activity for the decomposition of hydrogen peroxide (k = 2.02 × 10^?4 s^?1) in comparison with the homogenized Co(II)(acen)₂ complex (k = 4.32 × 10^?6 s^?1). The energy of activation for the decomposition of hydrogen peroxide with the heterogenized Co(II)(acen)₂ complex was low (38.52 kJ mol^?1) in comparison with that for the homogenized complex (73.44 kJ mol^?1). In both cases, the rate of decomposition of hydrogen peroxide was directly proportional to the concentration of hydrogen peroxide and cobalt(II) ions. On the basis of experimental observations, a rate expression for the decomposition of hydrogen peroxide was derived. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1398–1411, 2003     

Functionalized nanostructured silica by tetradentate-amine chelating ligand as efficient heavy metals adsorbent : Applications to industrial effluent treatment

Organofunctionalized nanostructured silica SBA-15 with tri(2-aminoethyl)amine tetradentate-amine ligand was synthesized and applied as adsorbent for the removal of Cu²⁺, Pb²⁺, and Cd²⁺ from both synthetic wastewater and real paper mill and electroplating industrial effluents. The prepared materials were characterized by XRD, N₂ adsorption-desorption, TGA, and FT-IR analysis. The Tren-SBA-15 was found to be a fast adsorbent for heavy metal ions from single solution with affinity for Cu²⁺, Pb²⁺, than for Cd²⁺ due to the complicated impacts of metal ion electronegativity. The kinetic rate constant decreased with increasing metal ion concentration due to increasing of ion repulsion force. The equilibrium batch experimental data is well described by the Langmuir isotherm. The maximum adsorption capacity was 1.85 mmol g^?1 for Cu²⁺, 1.34 mmol g^?1 for Pb²⁺, and 1.08 mmol g^?1 for Cd²⁺ at the optimized adsorption conditions (pH=4, T=323 K, t=2 h, C₀=3 mmol L^?1, and adsorbent dose=1 g L^?1). All Gibbs energy was negative as expected for spontaneous interactions, and the positive entropic values from 103.7 to 138.7 J mol^?1 K^?1 also reinforced this favorable adsorption process in heterogeneous system. Experiment with real wastewaters showed that approximately a half fraction of the total amount of studied metal ions was removed within the first cycle of adsorption. Hence, desorption experiments were performed by 0.3M HCl eluent, and Tren-SBA-15 successfully reused for four adsorption/desorption cycles to complete removal of metal ions from real effluents. The regenerated Tren-SBA-15 displayed almost similar adsorption capacity of Cu²⁺, Pb²⁺, and Cd²⁺ even after four recycles. The results suggest that Tren-SBA-15 is a good candidate as an adsorbent in the removal of Cu²⁺, Pb²⁺, and Cd²⁺ from aqueous solutions.     

Extraction and Adsorption Behavior of Co(II) on HTTA-Impregnated Polyurethane Foam

Abstract

The batch extraction of Co(II) from aqueous solutions with open cell polyethertype HTTA-loaded polyurethane (PU) foam has been studied using a radiotracer technique. The effect of pH, shaking time, and loading capacity has been investigated. The membrane properties of loaded PU foam sorbent offer unique advantage of adsorption. The fundamental studies of adsorption show that the classical Freundlich and Langmuir isotherms are followed in the entire concentration range of a 10^?5 to 10^?2 M solution of cobalt. The sorption mean free energy from the Dubinin-Radushkevich isotherm is found to be 13.8 kJ·mol^?1 and the loading capacity 4.44 mg·g^?1, suggesting that the ion-exchange or chemisorption mechanism operates. The kinetic parameters of adsorption also support a chemisorption mechanism and the first-order rate law. The rate constants and activation energies of sorption and desorption have been evaluated. The thermodynamic function of adsorption of ΔH, ΔS, ΔG, and equilibrium constant K _c have been calculated. The process of adsorption is established to be endothermic and chemisorption, stabilized through thermodynamic functions.     

Adsorption Thermodynamic and Kinetic Studies of Fluoride Aqueous Solution Treated with Waste Iron Oxide

This study uses a waste iron oxide material (BT3), which is a by-product of the fluidized-bed Fenton reaction (FBR–Fenton), for the treatment of a fluoride (F^?) solution. The purpose of this study is to investigate a low-cost sorbent as a replacement for the current costly methods of removing fluoride from wastewater. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) are used to characterize the BT3. Contact time, F^? concentration (from 0.75 to 6 mmol L^?1), and temperature (from 303 to 323 K) are used as operation parameters to treat the fluoride. The highest F^? adsorption capacity of the BT3 adsorbent was determined to be 1.17 mmol g^?1 (22.2 mg g^?1) for a 6 mmol L^?1 initial F^? concentration at pH 3.9 ± 0.2 and 303 ± 1 K. Adsorption data were well described by the Langmuir model, and the thermodynamic constants of the adsorption process, ΔG°, ΔH°, and ΔS°, were evaluated as ?1.63 kJ mol^?1 (at 303 K), ?1.75 kJ mol^?1, and ?52.4 J mol^?1 K^?1, respectively. Additionally, a pseudo-second-order rate model was adopted to describe the kinetics of adsorption. BT3 could be regenerated with NaOH, and the regeneration efficiency reached 95.1% when the concentration of NaOH was 0.05 mol L^?1.     

Performance of Unmodified Paper Solid Waste for Cadmium Removal From Aqueous Phase: Equilibrium and Kinetic Studies

The reuse of paper solid waste (PSW) as a low-cost sorbent for Cd removal from aqueous phase was investigated. Batch experiments were conducted to study the effects of pH (3.5, 5.5, 7.5), contact time (10–360 min), PSW dose (2.5–20 g L^?1), and Cd concentration (5–50 mg L^?1) at an ionic strength of 0.01 M NaNO₃ on adsorption efficiency and capacity. Cd removal of ～96% occurred in 20 mg L^?1 Cd solution at pH 5.5 containing 20 g L^?1 PSW. Equilibrium was attained after 120 min and the equilibrium adsorption capacity of PSW increased with increasing Cd concentration from 5 to 50 mg L^?1. The kinetic process of Cd adsorption obeyed the pseudo-second-order kinetic model. Langmuir and Freundlich models described equally well the experimental data and the maximum adsorption capacity was 4.89 mg g^?1. PSW can be used for reducing Cd concentration in Cd-contaminated water systems.     

Behaviors of Chemically Crosslinked CAAMPS Hydrogels in Uptake of Uranyl Ions from Aqueous Solutions

Uranyl ion adsorption from aqueous solutions has been investigated by chemically crosslinked (C) polyelectrolyte acrylamide/2-acrylamido-2-methyl-1-propanesulfonic acid (CAAMPS) hydrogels. CAAMPS hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), and water by free radical polymerization in an aqueous solution using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4 butanediol dimethacrylate (BDMA). The swelling equilibrium of polyelectrolyte copolymer gels containing of CAAMPS hydrogels has been studied as a function of copolymer composition. Swelling experiments were performed in water at 25°C, gravimetrically. The influence of AMPS content in hydrogels was examined. The weight-swelling ratio of CAAMPS hydrogels was increased up to 127.03 (for 300 mg AMPS and crosslinked by EGDMA) and 93.32 (for 300 mg AMPS and crosslinked by BDMA), while acrylamide hydrogels swelled up to 10.27 (crosslinked by EGDMA) and 10.06 (crosslinked by BDMA). Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of AMPS on the uranyl ion adsorption were examined. In the experiments of the sorption, L type sorption in the Giles classification system was found. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 0.67 × 10^?3–2.11 × 10^?3 mol uranyl ion per gram for CAAMPS hydrogels. Removal effiency of uranyl ions (RE%) was changed range 9.05–29.92%. The values of partition ratio, (K _d ) of uranyl ions was calculated to be 0.10–0.43 for CAAMPS hydrogels.     

Studies on two‐dimensional coordination polymer cadmium phosphate and its high efficient adsorption of Pb(II) ions from aqueous solutions

The two‐dimensional coordination polymer cadmium phosphate with the morphology of rectangle layers was prepared by solid‐state template reaction at room temperature, and was characterized by XRD, FTIR, and TEM techniques. The as‐synthesized sample is a layered cadmium phosphate material, in which the structure is poly (CdPO₄^?) anion framework with ammonium ions and water species residing in the space between the layers, and cadmium ions are coordinated by the phosphate oxygen atoms. This article also presents the adsorption of Pb(II) ions from aqueous solution on the as‐synthesized coordination polymer cadmium phosphate, and the results showed that this inorganic polymer adsorbent had good adsorption capacity. It could reach to the saturation adsorption capacity within an hour, and its excellent adsorption capacity for Pb(II) was 5.50 mmol/g when the initial solution concentration was 1.68 × 10³ μg/mL at T = 278K. Moreover, the adsorption kinetics and adsorption isotherms were studied, it revealed that the adsorption kinetics can be modeled by pseudo second‐order rate equation wonderfully. The apparent activation energy (E_a), ΔG, ΔH, and ΔS were 3.16 kJ mol^?1, ?13.97 kJ mol^?1, ?11.84 kJ mol^?1, and 7.66 J mol^?1 K^?1, respectively. And it was found that Langmuir equation could well interpret the adsorption of the as‐synthesized coordination polymer cadmium phosphate for Pb(II) ions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improved synthesis of a branched poly(ethylene imine)‐modified cellulose‐based adsorbent for removal and recovery of Cu(II) from aqueous solution

This study focuses on an improved synthesis of a branched poly (ethylene imine) (PEI)‐modified cellulose‐based adsorbent (Cell‐g‐PGMA‐PEI). We aim to improve the adsorbent capacity by reducing side reaction of epoxide ring opening during graft copolymerization of glycidyl methacrylate (GMA) onto cellulose which increases the content of epoxy groups, anchors to immobilize branched PEI moieties. FTIR spectra provided the evidence of successful graft copolymerization of GMA onto cellulose initiated by benzoyl peroxide (BPO) and modification with PEI. The amount of epoxy groups of Cell‐g‐PGMA was 4.35 mmol g^?1 by epoxy titration. Subsequently, the adsorption behavior of Cu(II) on cell‐g‐PGMA‐PEI in aqueous solution has been investigated. The data from the adsorption kinetic experiments agreed well with pseudo‐second‐order model. The adsorption isotherms can be interpreted by the Langmuir model with the maximum adsorption capacity of 102 mg g^?1 which was largely improved compared with the similar adsorbent reported. The dynamic adsorption capacity obtained from the column tests was 119 mg g^?1 and the adsorbent could be regenerated by HCl of 0.1 mol L^?1. Results indicate that the novel pathway for the synthesis of Cell‐g‐PGMA‐PEI exhibits significant potential to improve the performance of adsorbents in removal and recovery of Cu(II) from aqueous solution. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Paddle cactus (Tacinga palmadora) as potential low-cost adsorbent to treat textile effluents containing crystal violet

Abstract

The powdered biomass of paddle cactus (Tacinga palmadora), a rustic plant of great occurrence in the driest regions of Brazil, was evaluated as a low-cost adsorbent to treat textile effluents containing crystal violet (CV) dye. The powdered paddle cactus (PPC) was mainly composed by lignin and holocellulose, as well as, a variety of functional groups. Best results for CV adsorption were found using an adsorbent dosage of 0.5?g L^?1 at solution pH equivalent to 10.0. Fast adsorption kinetics was verified, being the equilibrium reached within 100?min, and the curves were well modeled by the pseudo-first-order model. The isotherms were well-represented by the Langmuir model. The maximum adsorption capacity was 228.74?mg g^?1 at 328?K. The estimated thermodynamics parameters were ΔG⁰_T?=?328K of –9.08?kJ mol^?1, ΔH⁰ of 12.44?kJ mol^?1, and ΔS⁰ of 0.065?kJ mol^?1 K^?1. In addition, PPC was able to treat a simulated textile effluent containing organic and inorganic compounds, reaching 93% of color removal efficiency. These findings show that powdered paddle cactus can be applied as potential low-cost adsorbent to treat textile effluents containing CV.     

Reactive separation of p-nitro phenol (PNP) from aqueous solution using tri-n-butyl phosphate: equilibrium and COSMO-RS studies

ABSTRACT

The present study is aimed to optimized diluent type, tri-n-butyl phosphate (TBP) composition and temperature for the reactive extraction of p-nitro phenol (PNP) in two different PNP concentration ranges [(0.00036–0.00646) kmol·m^?3 and (0.00646–0.01437) kmol·m^?3] as found in industrial effluents. 1-Octanol is investigated as the best diluent with TBP based on COSMO-RS theory. Equilibrium study based on mass action law is performed to find the insights of extraction mechanisms, equilibrium constant (K = 295.12 k·mol^?1) and stoichiometry (m:n = 1:1) as also confirmed by FTIR. Thermodynamic parameters, enthalpy (ΔH°), and entropy (ΔS°) are determined 27.51 K J mol^?1 and ?50.21 J mol^?1 K^?1, respectively.     

Syntheses and adsorption properties for Hg2+ of chelating resin of crosslinked polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole

A novel chelating resin with functional group containing S and N atoms was prepared using chloromethylated polystyrene and 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT) as materials. Its structure was characterized by infrared spectra and elementary analysis. The results showed that the content of the functional group was 2.07 mmol BMT g^?1 resin, 47% of which were in the form of monosubstitution (PS‐BMT‐1) and 53% in the form of double substitution (PS‐BMT‐2). The adsorption for mercury ion was investigated. The adsorption dynamics showed that the adsorption was controlled by liquid film diffusion. Increasing the temperature was beneficial to adsorption. The Langmuir model was much better than the Freundlich model to describe the isothermal process. The adsorption activation energy (E_a), ΔG, ΔH, and ΔS values calculated were 18.56 kJ·mol^?1, ‐5.99 kJ·mol^?1, 16.38 kJ·mol^?1, and 37.36, J·mol^?1·K^?1, respectively. The chelating resin could be easily regenerated by 2% thiourea in 0.1 mol·L^?1 HCl with higher effectiveness. Five adsorption–desorption cycles demonstrated that this resin was suitable for repeated use without considerable change in adsorption capacity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1646–1652, 2004     

A kinetic model for the adsorption of gold from I2/I− solutions onto a porous polymer membrane

A model for the adsorption of gold from I₂/I^? aqueous solutions onto a cellulose acetate (CA)‐polyaniline (PANI) porous membrane is presented. The adsorption of gold is represented by an ion‐exchange overall reaction in which AuI₂^? ions replace the Cl^? ions at the active sites of the polyaniline matrix. The model incorporates the external mass transfer of AuI₂^? from the bulk solution to the membrane surface, followed by the pore diffusion of AuI₂^? to reach the active sites in the membrane. The overall ion‐exchange reaction was assumed to achieve local instantaneous equilibrium. Verification of the kinetic model with the experimental data showed that the effective diffusivity of AuI₂^? within the membrane is about 8.3 × 10^?6 cm²/s. The potential applications of the present formulation are discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of fluorescent PEG-polyurethane with free carboxyl groups

An innovative spherical poly(vinyl alcohol)(PVA)/peat/clay porous composite bead was prepared and shown to be suitable for use as an adsorbent. The mass transport process for the adsorption of metal ions onto this composite bead in an aqueous system was investigated. In the external mass transport process, the diffusion coefficient (D₁) of Cu⁺² and Zn⁺² ions increased with increasing initial metal ion concentration and the increasing effect was more pronounced in the initial metal ion concentrations range of 18?×?10^-3 to 22?×?10^-3?M. The diffusion rate of Zn⁺² ions was faster than that of Cu⁺² ions. In the intraparticle diffusion process, the diffusion coefficient (D₂) decreased with increasing initial metal ion concentration in the initial concentration range of 1?×?10^-3 to 4?×?10^-3?M, and the value of D₂ maintained an almost constant value in the initial concentration range of 8?×?10^-3 to 22?×?10^-3?M. The rate of ion diffusion within the adsorbent for Cu⁺² ions was faster than that for Zn⁺² ions. The adsorption mechanism was controlled by the intraparticle diffusion process. The adsorption followed the Langmuir adsorption isotherm model. The maximum amount of adsorbed metal ions for Cu⁺² and Zn⁺² ions were 22.57 and 13.62?mg/g composite bead, respectively.