Crosslinking induced by irradiation raises selectivity of polymeric adsorbent

Amine‐type adsorbents were prepared by radiation‐induced graft polymerization. The sorption behaviors for an individual metal ion of Cu²⁺ and Pb²⁺ separately, as well as with mixed Cu²⁺/Pb^2+, were studied in both column and batch mode. Ethylenediamine‐type adsorbent exhibited a high capacity for Cu²⁺ and Pb²⁺ at a high flow rate of 1000 h^?1, but low selectivity in the mixed Cu²⁺/Pb²⁺ solutions. Radiation‐induced crosslinking of the amine‐type adsorbent was performed in water to improve selectivity. Crosslinking of the material was demonstrated by gel fraction, water content, and scanning electron microscopy image. Compared with the results from the noncrosslinked adsorbents, the breakthrough curve of Cu²⁺ right shifted, whereas the breakthrough curve of Pb²⁺ left shifted, indicating the higher adsorption capacity of Cu²⁺ and the lower adsorption capacity of Pb²⁺ from the crosslinked adsorbent. After 300 kGy irradiation, the crosslinked adsorbent was found to selectively adsorb Cu²⁺ from the mixed Cu²⁺/Pb²⁺ solution. The results revealed that crosslinking raised the selectivity of the adsorbents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of added metal ions on the interaction of chitin and partially deacetylated chitin with an azo dye carrying hydroxyl groups

The binding of chrome violet, which is a monoazo dye and involves two hydroxyl groups in the o and o′ positions to an azo group, to chintin and partially decetylated chitin, was examined in the presence of metal ions. Zn²⁺ and Cu²⁺ ions do not perceptively influence the binding affinity of chrome voilet to chitin. In contrast, Co²⁺ ion enhances the binding and Ni²⁺ ion suppresses it. In the lower free dye concentrations the dye uptake by partially deceteylated chitin was tremendously enhanced by adding. Co²⁺ ion in the buffer solution of pH 5. The dye uptake by the polymer was considerably increased by the addition of Cu²⁺ ion at pH 5 and became much larger at pH 6. The amount corresponded to that in the presence of Co²⁺ ion. To investigate further the action of added metal ions, a cobalt- or a chrome–complex dye was prepared, and the binding properties for the polymers were compared with those of chrome violet in the presence of Co²⁺ and Cu²⁺ ions. Some possible mechanisms for the enhancement of chrome violet binding by the addition of Co²⁺ and Cu²⁺ ions are described. © 1995 John Wiley & Sons, Inc.     

Synthesis of sulfhydryl chitin and its adsorption properties for heavy metal ions

This article discusses the preparation of the water‐insoluble adsorbent sulfhydryl chitin (s‐chitin), by treatment of the chitin with sulfhydryl acetic acid in the presence of sulfuric acid as a catalyst. Its structure was confirmed by elemental analysis, FTIR spectra analysis and near‐IR spectra analysis. We also investigated the adsorption properties of sulfhydryl chitin for Cu^II, Cd^II, Pb^II, Cr^III, and Ni^II. Based on the research results of adsorption capacity, the effect of pH value on adsorption, adsorption kinetics experiments, and selective adsorption experiments were observed. It has been shown that the s‐chitin has much better adsorption for Pb^II, Cu^II, and Cd^II than chitin itself. The adsorption capacities of s‐chitin for Pb^II, Cu^II, and Cd^II were 108.3, 94.7, and 57.1 mg/g, respectively. It also had good adsorption properties for heavy metal ions. The adsorption capacities were also affected by the acidity of medium. The adsorbed Cu^II, Cd^II, and Pb^II could be eluted by diluted chlorhydric acid. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 151–155, 2000     

Preparation and adsorption properties of metal ions of crosslinked chitosan azacrown ethers

The novel azacrown ether chitosan derivatives (CCAE‐I, CCAE‐II) were prepared by reaction between crosslinked chitosan with epoxy‐activated azacrown ethers. Their structures were confirmed by elemental FTIR spectra analysis and X‐ray diffraction analysis. The adsorption and selectivity properties of the crosslinked chitosan azacrown ethers for Pb²⁺, Cu²⁺, Cr³⁺, Cd²⁺, and Hg²⁺ were also investigated. The experimental results showed that they have high adsorption capacity for Cu²⁺, Cd²⁺, and Hg²⁺. The adsorption capacity of CCAE‐II is higher than CCAE‐I for Cd²⁺ and Hg²⁺. The selectivity properties of CCAE are better than chitosan and crosslinked chitosan. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3053–3058, 1999     

Cu2+ removal from aqueous solution by modified chitosan hydrogels

BACKGROUND: The adsorption of Cu²⁺ from aqueous solution using crosslinked chitosan hydrogels impregnated with Congo Red (CR) by ion‐imprint technology was systematically investigated with particular reference to the effects of contact time, pH, and initial concentration on adsorption. RESULTS: The adsorption capacity of the crosslinked chitosan without impregnation was only 68.68 mg g^?1 for Cu²⁺. However, the adsorption capacity increased from 77.42 (without imprint ion) to 84.54 mg g^?1 (imprint ion content 0.5 mmol) after the chitosan was impregnated with a ratio of 1/12 of CR to chitosan. The as‐prepared adsorbents were found to be pH‐dependent and the process of adsorption agreed well with the Freundlich isotherm. The loaded adsorbents could be regenerated and reused without the appreciable loss of capacity. CONCLUSION: Chitosan hydrogels impregnated with CR showed higher Cu²⁺ adsorption capacities compared with those prepared conventionally without imprint ion, and thus developed a good approach to increase Cu²⁺ adsorption efficiency in the treatment of waste‐water. Copyright © 2012 Society of Chemical Industry     

Synthesis of a polyacrylamide chelating resin and applications in metal ion extractions

A series of differently crosslinked polyacrylamide chelating resins were prepared, using N,N′-methylene-bis-acrylamide as the crosslinking agent. The crosslinked resins were functionalized by the reaction with ethylene diamine to get amino group capacities varying from 4.2 to 1.1 mequiv/g. The maximum adsorption capacities of the lightly crosslinked resin for Fe³⁺, Fe²⁺, Ni²⁺, and Cu²⁺ are 3.62, 4.22, 1.48, and 1.67 mequiv/g, respectively. The adsorbed metal ions can be quantitatively desorbed. The adsorption rate and the influence of pH on the adsorption of metal ions were examined. The resins can be used for the separation between different metal ions as well as the ions in different valence states (e.g., Fe³⁺ and Fe²⁺). The resin is amenable for continuous process and can be regenerated several times.     

Effect of deacetylation on sorption of dyes and chromium on chitin

Deacetylated chitins (10.7–67.2%) were prepared by alkaline hydrolysis to determine an optimal degree of deacetylation (DD) which can effectively remove four dyes and chromium ions from textile effluent. Sorption isotherms were carried by varying the treatment time, pH, and initial concentration of dyes or chromium ions. Experimental results were analyzed in three ways: (1) equilibrium sorption capacity and sorption rate constant, (2) Langmuir isotherms, and (3) separation factor. Results indicated that except for the chitin with a 67.2% DD, rate and capacity of the dye sorption on the chitin increased with the increase of the DD in chitin for each pH but decreased with the increase of pH for each deacetylated chitin. This was mainly due to the increase of—NH⁺₃ groups in chitin with a high DD and the low pH of the system. On the contrary, dye desorption from the deacetylated chitin was highly effective at 80° and pH ≥ 10, which could facilitate the reduction of—NH⁺₃ ions and the increase of electrostatic repulsion. The number of chromium ions sorbed on the chitin also increased with the increase of the DD at a specific time. Therefore, by controlling the DD of the deacetylated chitin maximum efficiency can be achieved in the removal of dyes and metal ions from textile effluent.     

Ethylenediamine tetraacetic acid modification of crosslinked chitosan designed for a novel metal‐ion adsorbent

Novel chitosan‐based adsorbent materials were synthesized with a higher fatty diacid diglycidyl as a crosslinking agent, and the adsorption ability of the resulting polymers for several metal ions was evaluated. Selective adsorption for Cu²⁺ in comparison with other divalent metal ions, such as Ni²⁺, Pb²⁺, Cd²⁺, and Ca²⁺, was observed with the crosslinked chitosan sorbent at pH 6; however, the adsorption power decreased abruptly as the pH value of the solution decreased. The addition of ethylenediamine tetraacetic acid (EDTA) residues to crosslinked chitosan significantly enhanced the adsorption power for metal ions, especially for Ca²⁺. The adsorptivity of Ca²⁺ was dramatically improved with the introduction of EDTA residues, and the value was greater than that obtained with a commercial chelate resin (CR11). Although the adsorption power of the EDTA‐derivatized sorbent for other metal ions was just comparable to that of the CR11 material, the newly synthesized adsorbent could be used for the recovery of metal ions from industrial waste solutions with a relatively wide range of pHs, from 4.0 to 6.0. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2758–2764, 2004     

Stability constants of amidoximated chitosan‐g‐poly(acrylonitrile) copolymer for heavy metal ions

Amidoximated chitosan‐g‐poly(acrylonitrile) (PAN) copolymer was prepared by a reaction between hydroxylamine and cyano group in chitosan‐g‐PAN copolymer prepared by grafting PAN onto crosslinked chitosan with epychlorohydrine. The adsorption and desorption capacities for heavy metal ions were measured under various conditions. The adsorption capacity of amidoximated chitosan‐g‐PAN copolymer increased with increasing pH values, and was increased for Cu²⁺ and Pb²⁺ but a little decreased for Zn²⁺ and Cd²⁺ with increasing PAN grafting percentage in amidoximated chitosan‐g‐PAN copolymer. In addition, desorption capacity for all metal ions was increased with increasing pH values in contrast to the adsorption results. Stability constants of amidoximated chitosan‐g‐PAN copolymer were higher for Cu²⁺ and Pb²⁺ but lower for Zn²⁺ and Cd²⁺ than those of crosslinked chitosan. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 469–476, 1999     

Polyethylenimine–polyepichlorohydrin interpolymer for chelating ion-exchange membrane

Polyethylenimine membranes consisting of linear polyethylenimine (PEI) and polyepichlorohydrin (PECH) were prepared by casting and heating an N,N-dimethylformamide solution of the two polymers under nitrogen at 100°C for 60 min. The membrane was also prepared by a heat-press method in a conventional manner. The cast membrane obtained was transparent. The membrane has a crosslinked structure due to the reaction between the secondary amino groups in PEI and the chloromethyl groups in PECH. Although a larger feed ratio of PEI/PECH gave membranes with a larger adsorption capacity for Cu²⁺ ions, the optimum ratio was 40/100 with respect to mechanical properties. A belt conveyor system using the PEI membrane was able to transport Cu²⁺ ions from one bath to another. In a diffusion dialysis against 1N HCl, the PEI membrane crosslinked rather tightly showed a specific ion-selective transfer character. For example, in Cu²⁺–Ca²⁺ system the permeability ratio P_cu/P_ca was about 3.8. The selectivity arises from the difference between affinities (extractabilities) of PEI toward metal ions. The selectivity was changed depending on the pH value.     

Synthesis of Copper and Lead Ion Imprinted Polymer Submicron Spheres to Remove Cu2+ and Pb2+

In this paper, Methacrylic acid (MAA) and 4-vinyl pyridine (4-VP) as functional monomers, Ethylene glycol two methyl acrylate (EGDMA) as crosslinking agent, isopropyl alcohol as the solvent, prepared the Cu(II)- and Pb(II)- imprinted polymers (IIPs) submicron spheres by precipitation polymerization. The presence/absence of the template ion in the preparation of the imprinted polymer was confirmed by EDX spectroscopy, and the structure of the particles was investigated using IR, SEM and BET analysis. From different components of crosslinker/monomer (C/M) ratio analysis, C/M at 1:3 was the optimal ratio for preparing IIPs. Atomic absorption spectroscopy (AAS) was characterized the imprinted polymers absorption behavior. The results show that the maximum adsorption capacity of Cu²⁺ and Pb²⁺ -imprinted polymer were 26.9 mg g^?1 and 25.3 mg g^?1, respectively. They also have good adsorption capacity and superior selectivity property for Cu²⁺ and Pb²⁺ in water, respectively. The selectivity factors (α) for Ni²⁺, Zn²⁺, Co²⁺ and Fe²⁺ were 16.5 (Cu²⁺) and 12.1 (Pb²⁺), 13.8 (Cu²⁺) and 16.2 (Pb²⁺), 10.8 (Cu²⁺) and 10.1 (Pb²⁺), 20.4 (Cu²⁺) and 20.7 (Pb²⁺), respectively. The regeneration experiment result demonstrates an excellent re-utilization property of these two type IIPs, after ten uses, the adsorption capacity can maintain above 60%.

     

Adsorption of copper on specifically modified polyamide sorbent

A novel, specific sorbent based on polyamide covalently immobilized with dead yeast cells by glutaraldehyde was prepared and characterized. This sorbent exhibits a high capacity for metal complexation based on multifunctional groups of dead cells, as well as a good stability for reuse based on the crosslinking agent, glutaraldehyde. The Cu²⁺ sorption characteristics of the polyamide modified with immobilized dead cells were studied and compared to those of the polyamide chemically modified without cells. The adsorption capacity of specifically modified polyamide was about 19‐fold higher than the chemically modified polymer. The adsorption isotherms of Langmuir and Freundlich for the new specific sorbent were determined. The effect of pH, temperature and co‐ions (Zn²⁺, Pb²⁺, Co²⁺, Ca²⁺ and Mg²⁺) on the Cu²⁺ sorption capacity were studied. The effectiveness of heavy metal desorption and the coefficient of recovery of sorption ability were determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 80–85, 2003     

Adsorption capacity,kinetics, and mechanism of copper(II) uptake on gelatin‐based hydrogels

Gelatin‐based hydrogels were synthesized and characterized for use as Cu²⁺‐ion sorbents. Gelatin was crosslinked in the presence of two different monomers, that is, acrylamide (AAm) and/or 2‐hydroxypropyl methacrylate, with N,N‐methylenebisacrylamide, ammonium persulfate, and sodium bicarbonate. The as‐prepared hydrogels were further characterized by scanning electron microscopy, Fourier transform spectroscopy, and the study of their swelling behavior as a function of temperature, time, and pH to evaluate their structure–property relationships. The hydrogels were observed to be good sorbents of Cu²⁺, and a maximum uptake of 84.8% was observed within 2 h at 37°C and with 10 ppm of the Cu²⁺‐ion solution for the gelatin and polyacrylamide hydrogel, which also exhibited the maximum retention capacity at 14.9 mg/g after four feeds. All of the experimental data exhibited good matches with the Langmuir isotherm and followed pseudo‐second‐order kinetics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal and radiation chemical stabilities of some polymers after Cu(II) build-up

The interaction of polyacrylic acid (PAA), polysodium acrylate (PAANa), polyacrylamide (PAM) and acrylic acid–acrylamide copolymer P(AM-AA) with copper sulphate was studied to evaluate the thermal and radiation chemical stabilities of the resultant polymers which contained increasing quantities of Cu^{2 +} . It was found that the efficiency of the polymers toward Cu^{2 +} interaction, as determined by XRF, follows the order P(AM-AA) > PAM > PAANa. PAA was inactive, and no Cu^{2 +} ions were detected. Generally, the results obtained from TGA and DSC reveal that there is an improvement in the thermal stability when Cu^{2 +} is incorporated into the polymer matrix, but the amount of Cu^{2 +} bound to the polymeric chains does not correlate with their relative thermal stability. The degree of crystallinity estimated by X-ray diffraction also increases as Cu^{2 +} is incorporated into the polymer. In addition to the thermal stability, the radiation chemical stability of polymer with accumulated Cu^{2 +} was found to be very high, so that the percentage of Cu^{2 +} released from the crosslinked polymers was zero at radiation doses of up to 500 kGy. © 1999 Society of Chemical Industry     

Structure and properties of films fabricated from chitin solution by coagulating with heating

In the present work, chitin films were fabricated from chitin solution dissolved in 8 wt % NaOH/4 wt % urea aqueous systems at low temperature by coagulating with heating without using any coagulant. The formation of the chitin films was confirmed to be an entirely physical process, namely chitin inclusion complex associated with NaOH, urea and water in the solvent was broken by heating, leading to the aggregation of the chitin chains through the hydrogen bonding. A schematic model was proposed to describe the regeneration mechanism of the chitin, indicating the physical crosslinking and entanglement of the chitin chains to form the films. Glycerol was used as plasticizer, and with an increase of the glycerol content, the elongation at break (?_b) of chitin films increased rapidly from 7.8 to 83.1%, whereas the tensile strength (σ_b) decreased from 89.3 to 51.7 MPa. This work provided a “green” pathway for the researches and developments of chitin materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39538.     

Relationship between electron sensitivity and chemical structures of polymers as electron beam resists. VI: Electron sensitivity of various acetalized poly(vinyl alcohol)s

Acetalized poly(vinyl alcohol)s which were synthesized from poly(vinyl alcohol) (PVA) and aldehyde or ketone were evaluated as electron beam (EB) resists, in order to investigate the relationship between EB sensitivity and chemical structures of the polymers. It was found that the acetalized PVAs were easily crosslinked by EB exposure. The main mechanism of crosslinking may be radical reaction at acetal group. The sensitivity of the acetalized PVA depended on the structure of the acetal group. Acetalized PVAs synthesized from benzaldehyde, in which the electron attracting group was substituted on the benzene ring and from linear aliphatic aldehyde having a long alkyl chain, had high sensitivity. A high sensitivity of 7.2 × 10^?7 C/cm² was attained when the acetalized PVA synthesized from p-chloro-benzaldehyde was used. Acetalized PVAs synthesized from PVA and aldehyde having a cyclic structure had an excellent dry etching durability and were suitable as negative EB resists.     

Synthesis and adsorption properties for metal ions of crosslinked chitosan acetate crown ethers

Two novel chitosan derivatives—crosslinked chitosan dibenzo‐16‐c‐5 acetate crown ether (CCTS‐1) and crosslinked chitosan 3,5‐di‐tert‐butyl dibenzo‐14‐c‐4 diacetate crown ether (CCTS‐2)—were synthesized by the reaction of crosslinked chitosan with dibenzo‐16‐c‐5 chloracetate crown ether and 3,5‐di‐tert‐butyl dibenzo‐14‐c‐4 dichloracetate crown ether with the intent of forming polymers that could be used in hazardous waste remediation as toxic metal‐binding agents in aqueous environments. Their structures were confirmed with elemental analysis, infrared spectral analysis, and X‐ray diffraction analysis. In the infrared spectra of CCTS‐1 and CCTS‐2, the characteristic peaks of aromatic backbone vibration appeared at 1595 cm⁻¹ and 1500 cm⁻¹; the intensity of the N H and O H stretching vibration in the region of 3150–3200 cm⁻¹ decreased greatly. The X‐ray diffraction analysis showed that the peak at 2θ = 20° decreased greatly in CCTS‐1 and CCTS‐2. The adsorption and selectivity properties of CCTS‐1 and CCTS‐2 for Pb²⁺, Cu²⁺, Cr³⁺, and Ni²⁺ were studied. Experimental results showed that the two crosslinked chitosan derivatives had not only good adsorption capacities for Pb²⁺, Cu²⁺, but also high selectivity for Pb²⁺, Cu²⁺ in the coexistence of Ni²⁺. For aqueous systems containing Pb²⁺, Ni²⁺, or Cu²⁺, Ni²⁺, CCTS‐1 only adsorbed Pb²⁺ or Cu²⁺. For aqueous systems containing Pb²⁺, Cr²⁺ and Ni²⁺, CCTS‐2 had high adsorption and selectivity properties for Pb²⁺. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2069–2074, 1999     

Preparation of crosslinked poly(styrene–g–N-carboxyalkylated ethylenimine) as chelating resin

Carboxymethyl and ethyl groups were introduced into crosslinked poly(styrene–g–ethylenimine) (PSt–g–EI), consisting of a crosslinked polystyrene backbone with linear polyethylenimine branches, by the reaction of PSt–g–EI with monochloroacetic acid and β-chloropropionic acid. Carboxyethylation was also performed by reaction of the PSt–g–EI with acrylic acid. The extent of the reaction was determined by the change in the nitrogen content of the resin. The adsorption of metal ions such as Cu²⁺, Cd²⁺, Hg²⁺, Ni²⁺, and Ca²⁺ by carboxyalkylated PSt–g–EI was examined. With the introduction of carboxyalkyl groups, the adsorption capacity for metal ions (per gram of resin) decreased, whereas the affinity of the resin for these ions increased.     

Adsorption of dyestuffs onto chitin. External mass transfer processes

The effect of several variables on the adsorption rate of four dyestuffs onto chitin was studied. A model is proposed enabling the film mass transfer coefficients to be determined. The coefficients were independent of initial dye concentration, chitin mass, chitin particle size, and temperature; a slight dependence with agitation was obtained. The film mass transfer coefficients at 400 rpm were 2.8×10^?3, 2.9×10^?3, 3.9×10^?3, and 0.9×10^?3 cm/s for Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 85, respectively.     

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