Enhanced and selective adsorption of mercury ions on chitosan beads grafted with polyacrylamide via surface-initiated atom transfer radical polymerization

Enhanced and selective removal of mercury ions was achieved with chitosan beads grafted with polyacrylamide (chitosan-g-polyacrylamide) via surface-initiated atom transfer radical polymerization (ATRP). The chitosan-g-polyacrylamide beads were found to have significantly greater adsorption capacities and faster adsorption kinetics for mercury ions than the chitosan beads. At pH 4 and with initial mercury concentrations of 10-200 mg/L, the chitosan-g-polyacrylamide beads can achieve a maximum adsorption capacity of up to 322.6 mg/g (in comparison with 181.8 mg/g for the chitosan beads) and displayed a short adsorption equilibrium time of less than 60 min (compared to more than 15 h for the chitosan beads). Coadsorption experiments with both mercury and lead ions showed that the chitosan-g-polyacrylamide beads had excellent selectivity in the adsorption of mercury ions over lead ions at pH < 6, in contrast to the chitosan beads, which did not show clear selectivity for either of the two metal species. Mechanism study suggested that the enhanced mercury adsorption was due to the many amide groups grafted onto the surfaces of the beads, and the selectivity in mercury adsorption can be attributed to the ability of mercury ions to form covalent bonds with the amide. It was found that adsorbed mercury ions on the chitosan-g-polyacrylamide beads can be effectively desorbed in a perchloric acid solution, and the regenerated beads can be reused almost without any loss of adsorption capacity.     

Adsorption of Hg(II) Ions onto Binary Biopolymeric Beads of Carboxymethyl Cellulose and Alginate

The removal of Hg(II) ions from aqueous solution by adsorption onto cross-linked polymeric beads of carboxymethyl cellulose (CMC) and sodium alginate was studied at fixed pH (6) and room temperature 28 ± 0.2°C. The cross-linked polymeric beads were characterized by FTIR spectra. Sorption capacity of the polymer for the mercury ions was investigated in aqueous media consisting different amounts of mercury ions (2.5 to 100 mg dm^?3) and at different pH values (2 to 8). Adsorption behavior of Hg(II) ions could be modeled using both the Langmuir and Freundlich isotherms. The dynamic nature of adsorption was quantified in terms of several kinetic constants such as rate constants for adsorption (k₁) and Lagergreen rate constant (K_ad). The influence of various experimental parameters such as effect of pH, contact time, solid-to-liquid ratio, salt effect, and temperature effect etc. were investigated on the adsorption of Hg(II) ions.     

Effect of the Solvent on the Water Properties of Water/Oil Microemulsions

Porous poly(styrene-divinylbenzene) (PS-DVB) particles were modified by adsorption of hydrophobically-modified dextrans, to provide chromatographic matrices for biomolecule chromatography. The dextran distribution and the pore characteristics of various coated PS-DVB beads were examined using nitrogen adsorption–desorption, mercury intrusion, and size exclusion chromatography. It was found that the adsorption of dextran does not result in homogeneous layers but rather in inhomogeneous ones. At high dextran loading and high content of hydrophobic groups in the adsorbed polymer, most of the pores of the macroporous rigid material are filled with a soft and porous dextran network being stabilized by hydrophobic interactions. According to chromatographic experiments, most of the surface was nevertheless expected to be covered at least by a thin and dense protecting layer since proteins—even those that are small enough to penetrate the dextran network—cannot interact nonspecifically with the internal pore surface. At low content of hydrophobic groups, dextran deposits preferentially as a thicker and more diffuse layer. However, the thickness of the coating is expected to be irregular and probably contributes to an increase in the roughness of the polystyrene surface.     

The electrocapillarity of polyacrylates

Summary The electrocapillary properties of polyacrylic acid have been studied by two methods. Exploratory measurements have been made of the effect of the polymer on the differential capacity of a mercury drop in 0.1 m sodium perchlorate. They showed that the polymer was strongly adsorbed over a wide range of potentials but that it did not appear to form a monolayer. The surface excess of polymer obtained from drop weight data showed a maximum at very low concentrations and then a decline at higher concentrations. The bulk of the work was carried out by making surface tension measurements, using a sessile mercury drop, in solutions of a fraction of polyacrylic acid (mol. wt. 7.02×10⁴) in potassium chloride at 0.01, 0.1, 0.2, and 0.5 m at 25°C.The data have been used to evaluate the surface excesses of the polymer and of the inorganic ions. The distribution of K⁺ and Cl^– in the electrical double layer and the contact adsorption of Cl^– on the mercury were very little affected by the presence of the polymer. The surface excess of polymer was always found to be greatest at low concentrations, to decrease steeply at first as the concentration was increased and then to decrease more slowly at higher concentrations.Possible explanations of this behaviour are discussed and it is concluded that the rapid decrease is a consequence of molecular weight dispersion and the stronger adsorption of high molecular weight polymer. The slow decrease in surface excess at higher concentrations may be a result of configurational changes of the polymer molecules.Surface pressure data show that, despite this decrease in the surface excess, the surface coverage reaches a high level at very low polymer concentrations and then continues to increase slowly as the concentration of polymer is increased. This apparent contradiction is due to changes in configuration of the adsorbed polymer molecules. At higher bulk concentrations the chain configurations are more compact and each adsorbed molecule makes more contacts with and so occupies a greater area of the mercury surface than at low concentrations.The conclusion is reached that the surface excess of polymer is mostly contained in a layer probably more than 1000 Å thick. It consists of a concentrated and entangled mass of polymer chains. Relatively few of these chains are in contact with the mercury at any istant. The concentration in this surface layer decreases steadily with increasing distance from the mercury surface and it merges without discontinuity into the bulk solution.With 10 figures in 22 details     

Biosorption of mercury by carboxymethylcellulose and immobilized Phanerochaete chrysosporium

Phanerochaete chrysosporium basidiospores immobilized onto carboxymethylcellulose were used for the removal of mercury ions from aqueous solutions. The biosorption of Hg(II) ions onto carboxymethylcellulose and both immobilized live and heat-inactivated fungal mycelia of Phanerochaete chrysosporium was studied using aqueous solutions in the concentration range 30-700 mg l⁻¹. The biosorption of Hg(II) ions by the carboxymethylcellulose and both live and heat-inactivated immobilized preparations increased as the initial concentration of mercury ions increased in the medium. Maximum biosorption capacity for immobilized live and heat-inactivated fungal mycelia of Phanerochaete chrysosporium was found to be 83.10 and 102.15 mg Hg(II) g⁻¹, respectively, whereas the amount of Hg(II) ions adsorbed onto the plain carboxymethylcellulose beads was 39.42 mg g⁻¹. Biosorption equilibria were established in approximately 1 h and the correlation regression coefficients show that the adsorption process can be well defined by a Langmuir equation. Temperature changes between 15 and 45 °C did not affect the biosorption capacity. The effect of pH was also investigated and the maximum adsorption of Hg(II) ions onto the carboxymethylcellulose and both live and heat-inactivated immobilized fungal mycelia was observed at pH 6.0. The carboxymethylcellulose-fungus beads could be regenerated using 10 mM HCl, with up to 95% recovery. The biosorbents were used in three biosorption-desorption cycles and no significant loss in the biosorption capacity was observed.     

Synthesis and Adsorption Performance of Surface‐Grafted Co(II)‐Imprinted Polymer for Selective Removal of Cobalt

The surface‐grafting ion‐imprinting technology was applied to synthesis of a new Co(II)‐imprinted polymer [Co(II)‐IP], which could be used for selective removal of Co(II) from aqueous solutions. The prepared polymer was characterized by using the infrared spectra (IR), X‐ray diffractometer (XRD), X‐ray energy dispersion spectroscopy (EDS) and scanning electron microscopy (SEM). The maximum adsorption capacity values for the Co(II)‐imprinted polymer and non‐imprinted polymer (NIP) were 22 and 8 mg/g, respectively. The Freundlich equation fitted the adsorption isotherm data well. The applicability of two kinetic models including pseudo‐first‐order and pseudo‐second‐order models was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity, and correlation coefficients. Results suggested that chemical process could be the rate‐limiting step in the adsorption process. And the adsorption of Co(II) on the Co(II)‐imprinted polymer was endothermic. The relative selectivity coefficients of the Co(II)‐imprinted polymer for Co(II)/Pb(II), Co(II)/Cu(II), Co(II)/Ni(II), Co(II)/Sr(II) and Co(II)/Cs(I) were respectively 11.5, 6.1, 13.8, 9.4, and 8.1 times greater than that of the non‐imprinted polymer. Eventually, the desorption conditions of the adsorbed Co(II) from the Co(II)‐imprinted polymer were also studied in batch experiments.     

Mimicking receptor for methylmercury preconcentration based on ion-imprinting

Solid-phase extraction (SPE) based on molecularly imprinted polymers (MIPs) were used to develop selective separation and preconcentration for methylmercury ion from complex matrixes. In this study, an ion-imprinting polymer was prepared to make artificial organomercury lyase preorganizing three methacryloyl-(l)-cysteine methylester (MAC) monomers and one methylmercury ion in a three-coordinate form by template polymerization, with the goal preparing a solid-phase which has the high selectivity for methylmercury ions.Methylmercury-imprinted beads were produced by a dispersion polymerization technique with use methylmercury-methacryloyl-(l)-cysteine (MM-MAC) complex monomer and ethylene glycoldimethacrylate (EDMA). After removal of methylmercury ions, methylmercury-imprinted beads were used for solid-phase extraction and determination of mercury compounds. Methylmercury adsorption and selectivity studies of methylmercury versus other metal ions which Hg(II), Zn(II), Pb(II) and Cd(II) were reported and distribution and selectivity coefficients of these ions with respect to methylmercury were calculated here.ICP-OES and HPLC-DAD determinations of methylmercury and mercury ions in the certified reference, LUTS-1 from the National Research Council of Canada and synthetic sea water showed that the interfering matrix had been almost removed during preconcentration. The methylmercury-imprinted solid-phase as mimic receptor was good enough for methylmercury determination in complex matrixes.     

Adsorptive removal of Cr(III) from aqueous solution using tripolyphosphate cross-linked chitosan beads

Chitosan tripolyphosphate (CTPP) beads were prepared at two different cross-linking densities and adsorption of Cr(III) onto it were studied as a function of different operational parameters such as solution pH, equilibration time and initial Cr(III) ion concentration. Higher cross-linked beads were found to have more adsorption capacity at all the experimental pH employed (pH = 3–5), whereas adsorption capacity is found to increase with increase in pH. Adsorption data were analyzed using Langmuir and Freundlich isotherm models. Langmuir model is found be more suitable to explain the experimental results with a monolayer adsorption capacity of 469.5 mg/g. Among the kinetic models used, pseudo-second order kinetic model could best describe the adsorption process. Competition experiments done in presence of Na(I), Mg(II), Ca(II), Al(III) and Fe(III) revealed that, except in the case of Al(III), adsorption of Cr(III) is not significantly affected by the presence of foreign cations. NaCl is found to be a suitable leaching agent for the desorption of adsorbed Cr(III) from CTPP beads. FTIR spectroscopic investigations confirmed that phosphate groups are the principal binding site responsible for the sorption of Cr(III) onto CTPP beads.     

Anion induced adsorption of Cd(II) from acetonitrile solutions

Solutions of Cd(II) in acetonitrile show no adsorption on mercury electrodes with sodium perchlorate as supporting electrolyte but strong adsorption of Cd(II) is produced by the addition of thiocyanate anion. The stoichiometry of the adsorbed species was shown to be Cd(NCS)₂ by means of chronocoulometric measurement of the quantities of both Cd(II) and NCS^? on the surface. The surface appears to reach a saturation coverage corresponding to ca. two monolayers of a tightly packed film. Speculations on the forces driving the adsorption are offered and similarities with previous results obtained in aqueous solutions are pointed out.     

Adsorption isotherm and atomic force microscopy studies of the interactions between polymers and surfactants on steel surfaces in hydrocarbon media

The adsorption isotherms for certain polymer and surfactant molecules (and in some cases their mixtures) on stainless steel beads from isooctane have been obtained, together with corresponding adsorbed layer thicknesses, using an atomic force microscope. The polymer is a terminally functionalised (ethylene diamine), low molecular weight polyisobutylene (PIB) derivative and the surfactants are basically alkyl or alkyl phenol alkoxylate molecules, which in one case has been derivatised with an amino functionality. The results indicate the presence of multilayers at the stainless steel-isooctane interface. Theoretical analysis of the surfactant adsorption isotherms suggests molecular aggregation at the interface with an aggregation number between 2 and 6, at the highest coverages. The adsorption of the polymer is reduced in the presence of the surfactant molecules. The polymer leaches metal ions from the steel surface at higher concentrations.     

钴(II)与色氨酸极谱催化前波的研究

对钴(II)离子与色氨酸在H~3BO~3-NaOH(pH=9)缓冲底液中的极谱催化前波进行了形成条件、吸附性能和电极还原过程的研究。     

Concanavalin a immobilized affinity adsorbents for reversible use in yeast invertase adsorption

Concanavalin A (Con A) immobilized poly(2-hydroxyethyl methacrylate) (PHEMA) beads were investigated for specific adsorption of yeast invertase from aqueous solutions. PHEMA beads were prepared by a suspension polymerization technique with an average size of 150-200 microm, and activated by epichlorohydrin. Con A was then immobilized by covalent binding onto these beads. The maximum Con A immobilization was found to be 10 mg/g. The invertase-loading capability of the PHEMA/Con A beads was 107 mg/g. The maximum invertase adsorption capacity on the PHEMA/Con A adsorbents was observed at pH 5.0. The values of the Michaelis constant K(m) of invertase were significantly larger upon adsorption, indicating decreased affinity by the enzyme for its substrate, whereas V(max) was smaller for the adsorbed invertase. Adsorption improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with adsorption. The adsorbed enzyme activity was found to be quite stable in repeated experiments. Storage stability of adsorbed invertase.     

Surface modification of poly(oligoethylene oxide methacrylate) for resisting protein adsorption

We prepare poly(2-methoxyethyl-, 2-(2-methoxyethoxy)ethyl-, 2-[2-(2-methoxyethoxy)ethoxy]ethyl methacrylate) (p(nEOMA), n=1, 2, and 3) brushed surfaces with varying the polymer density by surface initiated polymerization. The amount of bovine serum albumin (BSA) adsorbed on the surfaces is investigated. The mobility of the polymer chain in the polymer/water interfaces and the structure of adsorbed water on the surfaces are characterized by Electron Spin Resonance (ESR) and transmission-Fourier transform infrared (FT-IR) spectroscopy, respectively. This work reports the relationship between these surface properties and albumin adsorption. As a result, the surface having both a high molecular mobility and bulk-like water found to be very effective in preventing albumin adsorption.     

Non-equilibrium adsorption at solid/liquid interfaces from polyelectrolyte solutions

The poly(2-vinylpyridine) layer was established at the Pyrex glass/water interface with periodic phases of adsorption/desorption runs observed over several days. This was evidenced by determining the concentration of radio-labelled molecules in the solution equilibrating the glass beads as a function of time (the effluent) while the same radio-labelled polymer was slowly supplied by injecting the polymer solution into the reactor containing the adsorbent at a controlled extremely slow rate. Although the adsorption (or the desorption) steps seemed to present some periodic character, they were better correlated with the successive bulk concentration thresholds that were established with time when the initial surface was free of polymer at time zero. Even when the adsorbent was coated at different degrees, desorption steps were correlated to the overstepping of decreasing concentration thresholds. Adsorption and desorption runs were attributed to the existence of different typical interfacial conformations of the adsorbed macromolecules that only can be stabilised in the adsorbed state when the layer was equilibrated with the polymer solution of a certain concentration. Macromolecule were definitely adsorbed when the reconformation process led to a flat conformation (trains). Macromolecules adsorbed with a conformation close to their solution conformation may be desorbed as a result of the reconformation process affecting previously adsorbed neighbour molecules (in the case of partially coated surfaces at time zero of injection). Macromolecules with loops and tails were retained on the surface when the polymer concentration in the bulk was progressively increased (for uncoated surfaces at time zero of injection). All these effect were attributed to the combined influence of topological effects on adsorption and reconformation of adsorbed macromolecules that characterise the non-equilibrium adsorption processes.     

Voltammetric Determination of Mercury(II) at Poly(3‐hexylthiophene) Film Electrode. Effect of Halide Ions

The well‐known method for the determination of mercury(II), which is based on the anodic stripping voltammetry of mercury(II), has been adapted for applications at the thin film poly(3‐hexylthiophene) polymer electrode. Halide ions have been found to increase the sensitivity of the mercury response and shift it more positive potentials. This behavior is explained by formation of mercuric halide which can be easily deposited and stripped from the polymer electrode surface. The procedure was optimized for mercury determination. For 120 s accumulation time, detection limit of 5 ng mL^?1 mercury(II) has been observed. The relative standard deviation is 1.3% at 40 ng mL^?1 mercury(II). The performance of the polymer film studied in this work was evaluated in the presence of surfactants and some potential interfering metal ions such as cadmium, lead, copper and nickel.     

A study on the adsorption voltammetry of cobalt(II)—dime thylglyoxime system

The behaviour of the cobalt complex with dimethylglyoxime (DMG), Co(II)A₂, at the mercury electrode has been investigated in details. The adsorption phenomena have been observed by both normal pulse polarography and voltammetry with linearly changing potential. Experimental results show that, under the condition of adsorption potentials ranging from ?0.60 to ?0.9 eV (vs. S.C.E.), Co(II)A₂ can be adsorbed on the surface of hanging mercury drop electrode (HMDE) very well. The superficial concentrations represents a Langmuir isotherm with both concentration of Co(II)A₂ and the preconcentration time. The superficial concentration equation for adsorption voltammetry, corresponding to the condition of the low coverage of the electrode surface, is deduced. The equation has been verified experimentally. The sensitivity of the proposed method, which has been analysed theoretically, is independent on the scan rate and the surface area of HMDE, but depends on the preconcentration time and the diffusion layer thickness. For the 120 sec accumulation, the lower limit of determination is 1.10^?9 M.     

Adsorption of block polyampholyte micelles in monolayers at the silicon water interface

 The adsorption of the diblock polyampholyte poly (methacrylic acid)-block-poly((dimethylamino)ethyl methacrylate) from aqueous solution on silicon substrates was investigated as a function of polymer concentration and pH. Dynamic light scattering and electrokinetic measurements were used to characterize the polyampholyte in solution. The amount of polymer adsorbed was determined by ellipsometry and lateral structures of the polymer layer were investigated by scanning force microscopy. The amount of polymer adsorbed was found to be strongly influenced by the pH of the polymer solution, while the size of the polyampholyte micelles adsorbed on the surface was hardly affected by pH during adsorption. From investigations by scanning force microscopy well-seperated micelles were seen in the dried monolayers adsorbed directly from solution. The structures at the surface are correlated to structures in solution, and the adsorbed amount depends on the relative charge of the micelles and the surface. Received: 13 September 1999 Accepted in revised form: 8 December 1999     

Fe(II)-脱乙酰壳聚糖配位聚合物的合成及其性能表征

本文探讨了壳聚糖对Fe(Ⅱ）的吸附条件，并对壳聚糖与Fe(Ⅱ)的吸附行为进行了详细研究，认为Fe(Ⅱ)与壳聚糖既发生配位反应形成Fe(Ⅱ)-壳聚糖配位聚合物，也产生吸附作用，并通过红外光谱和紫外光谱证实了Fe(Ⅱ)与壳聚糖之间发生了配位作用。     

Layer-by-layer self-assembly polytungstogermanate multilayer films and their photocatalytic properties under sunlight irradiation

Seven different types of thio- and/or amine-modified cellulose resin materials were synthesized and their mercury (II) ion adsorption properties determined. All seven resins showed good mercury (II) adsorption capability in the more neutral pH regions. However, the o-benzenedithiol- and o-aminothiophenol-modified cellulosic resins were found to be very effective in removing mercury (II) ions from strongly acidic media. For example, 93.5-100% mercury (II) ion recoveries from very acid aqueous solutions (nitric acid concentration ranged from 0.1 to 2.0 mol/L) were obtained using the o-benzenedithiol-modified resin while recoveries ranged from ca. 50% to 60% for the o-aminothiophenol-modified resin. An adsorption capacity of 23 mg (as Hg atoms) per gram of resin was observed for the o-benzenedithiol-modified cellulose in the presence of 1.0 mol/L nitric acid. This same resin shows very good selectivity for mercury (II) as only ruthenium (II) also somewhat adsorbed onto it out of 14 other metal ions studied (Ag(+), Al(3+), As(3+), Co(2+), Cd(2+), Cr(3+), Cu(2+), Fe(3+), Mn(2+), Ni(2+), Pt(2+), Pb(2+), Ru(2+), and Zn(2+)).     

Poly(acrylamide) grafts on spherical bead polymers for extremely selective removal of mercuric ions from aqueous solutions

Poly(acrylamide) grafted from solid polymer particles provides a simple solution for extremely selective removal of mercuric ions from aqueous solutions. The grafting of polyacrylamide has been performed, in high yields (164%), by redox initiation from iminoacetic acid groups created on crosslinked spherical beads (210–420 μm) of glycidyl methacrylate/methyl methacrylate/ethylene glycol dimethacrylate terpolymer. In the grafting, homopolymer formation has been reduced greatly (22%) by the treatment of the bead polymer with ceric ammonium nitrate before the addition of acrylamide monomer. The mobility of the graft chains provides nearly homogeneous reaction conditions and rapid mercury binding ability, as for low molecular weight amides [mercury sorption by a 0.105‐g polymer sample from 105 mL of a 7.74 × 10^?4 mol L^?1 (～155 ppm) Hg(II) solution shows first‐order kinetics with respect to the Hg(II) concentration, k = 1.1 × 10^?3 s^?1]. The mercury sorption capacity under nonbuffered conditions is around 3.6 mmol g^?1 (i.e., 720 g of mercury/kg) and mostly occurs with the formation of diamido–mercury linkages, which result in the crosslinking of polyacrylamide brushes outside the spherical beads. The crosslinks can be destroyed by treatment with hot acetic acid, without hydrolysis of the amide groups. This process allows a complete elution of the mercury as mercury acetate, and the overall result is reversible crosslinking of the outer shell by mercuric ions. The material presented is efficient in the removal of mercury at concentrations measured in parts per million, and the mercury sorption is extremely selective over some foreign ions, such as Fe(III), Cd(II), Zn(II), and Pb(II). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3068–3078, 2002