Synthesis and characterization of poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-glutamic acid) copolymer beads for removal of lead ions

N-methacryloyl-(l)-glutamic acid (MAGA) was synthesized using methacryloyl chloride and l-glutamic acid methyl ester as a metal-complexing ligand and/or comonomer. MAGA was characterized by FTIR and NMR. Spherical beads with an average diameter of 150–200 μm were obtained by suspension polymerization of MAGA and 2-hydroxyethyl methacrylate (HEMA) performed in an aqueous dispersion medium. Poly(HEMA-MAGA) beads were characterized by swelling studies, surface area measurements and elemental analysis. Poly(HEMA-MAGA) beads have a specific surface area of 56.7 m²/g. Poly(HEMA-MAGA) beads were used in the removal studies of Pb²⁺ ions. Adsorption equilibrium was achieved in about 60 min. The adsorption of Pb²⁺ ions onto PHEMA beads was negligible (0.38 mg/g). The MAGA incorporation into the polymer structure significantly increased the lead adsorption capacity (348 mg/g). The adsorption of Pb²⁺ ions increased with increasing pH and reached a plateau value at around pH 5.0. Competitive adsorption of heavy metal ions from synthetic wastewater was also studied. The adsorption capacities are 42.5 mg/g for Pb²⁺, 26.8 mg/g for Hg²⁺ and 17.6 mg/g for Cd²⁺ at 0.5 mmol/l metal concentration. Consecutive adsorption and elution operations showed the feasibility of repeated use for poly(HEMA-MAGA) chelating beads.     

Glutamic acid containing supermacroporous poly(hydroxyethyl methacrylate) cryogel disks for UO22+ removal

Supermacroporous cryogel with an average pore size of 10–200 μm in diameter was prepared by cryopolymerization of N-methacryloyl-(l)-glutamic acid (MAGA) and 2-hydroxyethyl methacrylate (HEMA). The poly(HEMA–MAGA) cryogel was characterized by surface area measurements, FTIR, swelling studies, elemental analysis and SEM. The poly(HEMA–MAGA) cryogel had a specific surface area of 23.2 m²/g. The equilibrium swelling ratio of the cryogel is 9.68 g H₂O/g for poly(HEMA–MAGA) and 8.56 g H₂O/g cryogel for PHEMA. The poly(HEMA–MAGA) cryogel disks with a pore volume of 71.6% containing 878 μmol MAGA/g were used in the removal of UO₂²⁺ from aqueous solutions. Adsorption equilibrium of UO₂²⁺ was obtained in about 30 min. The adsorption of UO₂²⁺ ions onto the PHEMA cryogel disks was negligible (0.78 mg/g). The MAGA incorporation significantly increased the UO₂²⁺ adsorption capacity (92.5 mg/g). The adsorption process is found to be a function of pH of the UO₂²⁺ solution, with the optimum value being pH 6.0. Adsorption capacity of MAGA contained PHEMA based cryogel disks increased significantly with pH and then reached the maximum at pH 6.0. Consecutive adsorption and elution cycles showed the feasibility of repeated use for poly(HEMA–MAGA) cryogel disks.     

Cadmium removal out of human plasma using ion-imprinted beads in a magnetic column

The aim of this study is to utilize ion-imprinted magnetic beads in the selective removal of Cd²⁺ ions out of human plasma overdosed with Cd²⁺ ions. The Cd²⁺ imprinted magnetic poly(HEMA-MAC) (mPHEMAC-Cd²⁺) beads were produced by suspension polymerization in the presence of magnetite Fe₃O₄ in a nano-powder form. The template Cd²⁺ ions could be reversibly detached from the matrix to form mPHEMAC-Cd²⁺ beads using 0.1 M thiourea solution. The specific surface area of the mPHEMAC-Cd²⁺ beads was found to be 24.7 m²/g. The MAC and Fe₃O₄ contents of the mPHEMAC-Cd²⁺ beads were found to be 41.8 µmol/g polymer and 8.2% on the average. The Cd²⁺ adsorption capacity of mPHEMAC-Cd²⁺ columns decreased drastically from 48.8 µmol/g to 20.0 µmol/g as the flow rate is increased from 0.50 ml/min to 3.0 ml/min. The maximum adsorption capacity of the mPHEMAC-Cd²⁺ beads was determined to be 48.8 µmol Cd²⁺/g on the average. The relative selectivity coefficients of the mPHEMAC beads for Cd²⁺/Pb²⁺ and Cd²⁺/Zn²⁺ were 22.6 and 160.7 times greater than those of the non-imprinted magnetic PHEMAC (mPHEMAC) beads, respectively. The mPHEMAC-Cd²⁺ beads are reusable for many times with no significant decrease in their adsorption capacities.     

N-methacryloyl-(l)-histidine methyl ester carrying porous magnetic beads for metal chelate adsorption of cytochrome c

A magnetic metal-chelate adsorbent utilizing N-methacryloyl-(l)-histidine methyl ester (MAH) as a metal-chelating ligand was prepared. MAH was synthesized using methacryloyl chloride and l-histidine methyl ester. Magnetic beads with an average diameter of 50–100 μm were produced by suspension polymerization of ethylene glycol dimethacrylate (EGDMA) and MAH carried out in a dispersion medium. Specific surface area of the magnetic beads was found to be 80 m²/g. Elemental analysis of the magnetic beads for nitrogen was estimated as 70 μmol MAH/g polymer. Magnetic beads were complexed with the Cu²⁺ ions directly via MAH for the adsorption of cytochrome c from aqueous solutions. The cytochrome c adsorption on the mag-poly(EGDMA–MAH) beads was 51 mg/g. Cu²⁺ complexing increased the cytochrome c adsorption significantly. The maximum cytochrome c adsorption capacity of the Cu²⁺-chelated beads (carrying 68 μmol Cu²⁺ per gram of polymer) was found to be 222 mg/g at pH 8.0 in phosphate buffer. Cytochrome c adsorption decreased with increasing temperature. Cytochrome c molecules could be reversibly adsorbed and desorbed ten times with the magnetic adsorbents without noticeable loss in their cytochrome c adsorption capacity. The resulting magnetic chelator beads posses excellent long term storage stability.     

Hydrophobic microbeads as an alternative pseudo-affinity adsorbent for recombinant human interferon-α via hydrophobic interactions

Hydrophobic interaction chromatography (HIC) is increasingly used for protein purification, separation and other biochemical applications. The aim of this study was to prepare hydrophobic microbeads and to investigate their recombinant human interferon-α (rHuIFN-α) adsorption capability. For this purpose, we had synthesized functional monomer, N-methacryloyl-l-phenylalanine (MAPA), to provide a hydrophobic functionality to the adsorbent. The poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-phenylalanine) [poly(HEMA–MAPA)] microbeads were prepared by suspension copolymerization. microbeads were characterized using FTIR, swelling behavior, and SEM micrographs. Equilibrium swelling ratio of poly(HEMA–MAPA) and poly(HEMA) microbeads were 53.3% and 69.3%, respectively. The specific surface area and average pore diameters determined by BET apparatus were 17.4 m²/g and 47.3 Å for poly(HEMA) microbeads and 18.7 m²/g and 49.8 Å for poly(HEMA–MAPA) microbeads. Adsorption experiments were performed under different conditions. Maximum rHuIFN-α adsorption capacity was found to be 137.6 ± 6.7 mg/g by using poly(HEMA–MAPA) microbeads with a size range of 150–250 μm and containing 327 μmol MAPA/g microbeads. Compared with poly(HEMA–MAPA) microbeads, nonspecific rHuIFN-α adsorption onto plain poly(HEMA) microbeads was very low, about 4.2 ± 2.3 mg/g. To determine the effects of adsorption conditions on possible conformational changes of rHuIFN-α structure, fluorescence spectrophotometry was employed. Repeated adsorption–elution processes showed that these microbeads are suitable for repeatable rHuIFN-α adsorption.     

Characterization of new sorbent constructed from Fe3O4/chitin magnetic beads for the dynamic adsorption of Cd2+ ions

Novel magnetic chitin (CM) beads were successfully prepared by in situ synthesis of Fe₃O₄ nanoparticles in regenerated chitin beads (Ch beads) for the packing fixed-bed columns. The interpenetrated porous structure in the regenerated Ch beads at the swollen state served as templates for the inorganic nanoparticle preparation. The morphology and structure of the hybrid nanomaterials were characterized with scanning transmission electron microscopy, transmission electron microscopy, thermal gravimetry analysis, X-ray diffraction, and Fourier transform infrared spectroscopy, and the Cd²⁺ ion adsorption capacity of the CM beads was determined by UV–Vis spectrophotometry. The results revealed that the CM beads exhibited efficient adsorption of Cd²⁺ ions in the aqueous solution, as a result of the microporous structure, large surface area, and affinity for metal ions. The equilibrium process of this fixed-bed column was well described by Thomas and Bohart–Adams model, indicating that the external mass transfer was the rate-limiting process at the beginning of adsorption. The adsorption equilibrium was better described by the bed depth–service time model, indicating that the Cd²⁺ uptake could be controlled by external mass transfer at the beginning and intraparticle diffusion at a later stage of the adsorption. The CM beads loaded with the Cd²⁺ could be regenerated and reused easily. The CM beads should have potential applications in the chromatography packing and adsorbent both at the laboratory and industrial scales.     

Amino-functionalized Fe3O4/SiO2 magnetic submicron composites and In3+ ion adsorption properties

Five kinds of amino-functionalized (polyaniline, poly(1,2-diaminobenzene), poly(1,3-diaminobenzene), poly(diphenylamine), and poly(o-toluidine)) Fe₃O₄/SiO₂ submicron composites (SCs) were prepared. The SEM and TEM results showed that these SCs possessed a sphere-like core/shell structure with an average diameter of ~500 nm. The XRD results indicated good crystallinity of Fe₃O₄ core, the amorphous SiO₂, and amino-functionalized shells. The XPS results confirmed that amino groups were plentiful rich outside the surface of these SCs which acted as the effective groups for adsorbing the metal ions. These SCs showed a good thermal stability at 20–250 °C. The high saturation magnetization of 60–70 emu/g is better than other similar reports. In³⁺ adsorption coefficients from aqueous solution by these SCs were higher than 10⁶ mL/g, indicating the higher selectivity and affinity to In³⁺ compared with Cd²⁺ and Hg²⁺ ions. In addition, these SCs could be magnetically reclaimed within 30 s and regenerated with acid after adsorption. The adsorption capabilities only decreased by 6 % after five cycles. The present work indicates that the amino-functionalized Fe₃O₄/SiO₂ SCs are promising for removal of In³⁺ ions in field application.     

Synthesis of Cr(VI)-imprinted poly(4-vinyl pyridine-co-hydroxyethyl methacrylate) particles: its adsorption propensity to Cr(VI)

The aim of this study is to prepare ion-imprinted polymers, which can be used for the selective removal of Cr(VI) anions from aqueous media. 4-Vinyl pyridine (4-VP) was used as functional monomer. The Cr(VI)-imprinted poly(4-vinyl pyridine-co-2-hydroxyethyl methacrylate), poly(VP-HEMA), particles were prepared by bulk polymerization. The Cr(VI)-imprinted polymer particles were grained from the bulk polymer, and the template ions (i.e., Cr(VI)) were removed using thiourea (0.5%, v/v) in 0.5M HCl. The Cr(VI)-imprinted polymer contained 21.4 μmol 4-VP/g polymers. The specific surface area of the IIP2 particles was found to be 34.5m(2)/g (size range of 75-150 μm), and the swelling ratio was about to 108%. The effect of initial concentration of Cr(VI) anions, the adsorption rate and the pH of the medium on adsorption capacity of Cr(VI)-imprinting polymer were studied. The maximum experimental adsorption capacity was 3.31 mmol Cr(VI)/g polymer. Under competitive condition, the adsorption capacity of Cr(VI)-imprinted particles for Cr(VI) is 13.8 and 11.7 folds greater than that of the Cr(III) and Ni(II) ions, respectively. The first- and second order kinetics models were estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. The Langmuir adsorption isotherm model was well described the Cr(VI)-imprinted system and the maximum adsorption capacity (Q(max)) was found to be 3.42 mmol/g. Moreover, the reusability of the poly(VP-HEMA) particles was tested for several times and no significant loss in adsorption capacity was observed.     

Local Environment of Fe Ions in a 40ZnO · 60B<Subscript>2</Subscript>O<Subscript>3</Subscript> Glass Matrix

The valence state and coordination environment of the Fe ions in a number of Fe-containing zinc borate glasses with the general formula xFe₂O₃–(100–x)[40ZnO · 60B₂O₃] (x = 2.5–10 mol %) have been studied by Mössbauer spectroscopy. The results indicate that all of the glasses contain both Fe²⁺ and Fe³⁺ ions. The percentage of trivalent ions considerably exceeds that of Fe²⁺ ions and the relationship between the Fe²⁺ and Fe³⁺ concentrations is essentially independent of the Fe₂O₃ content in the zinc borate matrix. Most of the Fe³⁺ ions are in tetrahedral coordination, but raising the Fe₂O₃ content to above 5 mol % leads to a gradual increase in the percentage of Fe ions in octahedral coordination.     

Molecular imprinted particles for lysozyme purification

Molecular recognition-based separation techniques have received much attention in chemistry and biology because of their high selectivity for target molecules. The aim of this study is to prepare lysozyme-imprinted polymers which can be used for the purification of lysozyme from aqueous solutions and egg white. N-methacryloyl-(l)-histidinemethylester (MAH) was chosen as the metal-complexing monomer. In the first step, Cu²⁺ was complexed with MAH and the lysozyme-imprinted poly(HEMA–MAH) [Lys-MIP] particles were synthesized by UV-initiated bulk polymerization. After that, the template (i.e., lysozyme) were removed using 0.1 M NaCl solution. The specific surface area of the Lys-MIP particles was found to be 22.9 m²/g with a size range of 20–63 μm in diameter and the swelling ratio was 57%. According to the elemental analysis results, the particles contained 421 μmol MAH/g polymer. The maximum lysozyme adsorption capacity was 12.1 mg/g polymer. The relative selectivity coefficients of imprinted particles for lysozyme/human serum albumin and lysozyme/cytochrome c were 3.6 and 4.1 times greater than NIP particles, respectively. Purification of lysozyme from egg-white was also monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. The purity of the desorbed lysozyme was about 89% with recovery about 84%. The Lys-MIP particles could be used many times without decreasing their adsorption capacities significantly.     

The study of adsorption characteristics Cu and Pb ions onto PHEMA and P(MMA-HEMA) surfaces from aqueous single solution

The adsorption characteristics of Cu²⁺ and Pb²⁺ ions onto poly2-hydroxyethyl methacrylate (PHEMA) and copolymer 2-hydroxyethyl methacrylate with monomer methyl methacrylate P(MMA-HEMA) adsorbent surfaces from aqueous single solution were investigated with respect to the changes in the pH of solution, adsorbent composition (changes in the weight percentage of MMA copolymerized with HEMA monomer), contact time and the temperature in the individual aqueous solutions. The linear correlation coefficients of Langmuir and Freundlich isotherms were obtained. The results revealed that the Langmuir isotherm fitted the experimental results better than the Freundlich isotherm. Using the Langmuir model equation, the monolayer adsorption capacity of PHEMA surface was found to be 0.840 and 3.037 mg/g for Cu²⁺ and Pb²⁺ ions and adsorption capacity of (PMMA-HEMA) was found to be 31.153 and 31.447 mg/g for Cu²⁺ and Pb²⁺ ions, respectively. Changes in the standard Gibbs free energy (ΔG⁰), standard enthalpy (ΔH⁰) and standard entropy (ΔS⁰) show that the adsorption of mentioned ions onto PHEMA and P(MMA-HEMA) are spontaneous and exothermic at 293–323 K.     

Heavy metal ions adsorption and photodegradation of remazol black XP by iron oxide/silica monoliths: Kinetic and equilibrium modelling

The adsorption of heavy metal ions (Cr³⁺, Pb²⁺ and Cd²⁺) by metal oxide monoliths (Fe₂O₃ and Fe₂O₃/SiO₂) synthesized via nanocasting method using SiO₂ monoliths as a template was studied. The adsorption experiments were performed in different batches by varying key parameters and the equilibrium between the adsorbents and metal ion solution was achieved in ～120?min at pH 6. The maximum monolayer adsorption efficiency for Pb (II), Cr (III) and Cd (II) ions was 850, 770 and 690?mg/g, respectively, for the magnetic Fe₂O₃/SiO₂ monoliths. The experimental data show best fit with the pseudo-second-order reaction type. The adsorption data found to be well fitted using Freundlich and Langmuir adsorption isotherms. The adsorption process was exothermic and spontaneous in nature, as confirmed by the thermodynamic parameters. Furthermore, the photocatalytic degradation of an industrial dye e.g., remazol black XP (RxP) by Fe₂O₃/SiO₂ monoliths was done from wastewater and the photocatalytic efficiency of the monoliths (using different amount) has been evaluated under visible light source which gives the best results (97.8%) for the monolith concentration 0.10?g/L.     

Preparation and characterization of zeolite from waste Linz-Donawitz (LD) process slag of steel industry for removal of Fe3+ from drinking water

Cubical-shaped zeolite A was synthesized from the Linz-Donawitz (LD) process slag of the Steel Industry, utilizing conventional fusion-assisted hydrothermal treatment. Morphological and Physico-chemical characterizations were performed by various characterization techniques. A weight ratio of 1:1.2 (LD-slag: NaOH) was maintained during fusion, which provides a better binding effect with better mechanical stability to the zeolite framework. Fe³⁺ adsorption studies were performed at 273, 298, 303, and 308 K, respectively, within the range of 10–40 mg L⁻¹ Fe³⁺ ion concentration for kinetic and isotherm studies. A maximum adsorption capacity of 27.55 mg g⁻¹ was obtained at a 1.4 g L⁻¹ adsorbent dosage, with 99.99% Fe³⁺ ion removal. Moreover, the Fe³⁺ adsorption study obeyed the pseudo-second-order kinetic model, whereas multistage diffusion controlled the adsorption process. Langmuir isotherm model best fitted the equilibrium data suggesting the highly negative charge over the adsorbent surface played a vital role in the electrostatic attraction of Fe³⁺ ions. Isomorphic replacement of silicon by aluminum ion imparted a highly negative charge over the zeolite surface in the primary structure unit. For real-life sample drinking water, the Fe³⁺ ion removal efficiency increases to 97.7%.     

Hydrophobic nano-carrier for lysozyme adsorption

In this work, poly(HEMA–APH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique. Magnetic behaviour was introduced by simple addition of Fe₃O₄ into the polymerization medium. Characterization of the nanoparticle was carried out by FTIR, ESR, SEM, AFM and EDX analyses. These synthesized magnetic nanoparticles were used for adsorption of lysozyme. For this purpose, adsorption conditions were optimized and maximum lysozyme binding capacity was found to be 278.8 mg g^?1 polymer in pH 7.0 phosphate buffer at 25^°C. Desorption and reusability properties of the nanoparticles were investigated and lysozyme adsorption efficiency did not change significantly at the end of the 10 successive reuses.     

Highly selective ion-imprinted particles for solid-phase extraction of Pb ions

The Pb²⁺-imprinted (PHEMAC-Pb²⁺) particles were prepared by bulk polymerization as a solid-phase extraction (SPE) adsorbent. N-methacryloyl-(l)-cysteine (MAC) was used as functional monomer to have a well-shaped molecular geometry between MAC monomer and Pb²⁺ ions that provide molecular recognition based on well fitted cavities for Pb²⁺ ions after removal of template ions. The PHEMAC-Pb²⁺ particles were characterized and the applicability of these particles was investigated for the solid-phase extraction of Pb²⁺ ions from aqueous solutions and environmental samples. The PHEMAC-Pb²⁺ particles with a size range of 50–200 µm have a rough surface and macropores in bulk structure. The adsorption capacity of the PHEMAC-Pb²⁺ particles is relatively low (2.01 mg/g). However, the high selectivity towards competitive ions (Cd²⁺, Ni²⁺ and Cu²⁺) promises the PHEMAC-Pb²⁺ particles an alternative SPE adsorbent in literature. The relative selectivity coefficients of PHEMAC-Pb²⁺ particles for Pb²⁺/Ni²⁺, Pb²⁺/Cd²⁺ and Pb²⁺/Cu²⁺ were almost 71, 117 and 192 times greater than that of non-imprinted (PHEMAC) particles, respectively. Moreover, the reusability of the PHEMAC-Pb²⁺ particles was tested for several times and no significant loss in adsorption capacity was observed. The accuracy of the proposed procedure was also verified by the determination of Pb²⁺ ions in the certified reference material, LGC 6137 Estuarine sediment.     

Poly(glycidyl methacrylate) beads embedded cryogels for pseudo-specific affinity depletion of albumin and immunoglobulin G

Depletion of high abundant proteins like albumin and immunoglobulin G (IgG) can be beneficial in the analysis of serum proteins. For this purpose, Cibacron Blue F3GA and iminodiacetic acid (IDA)-Cu²⁺ containing poly(glycidyl methacrylate) (PGMA) beads (1.6 µm in diameter) were embedded into the poly(hydroxyethyl methacrylate) (PHEMA) cryogel. The PGMA beads were prepared by dispersion polymerization. The PGMA beads were modified with Cibacron Blue F3GA and iminodiacetic acid (IDA)-Cu²⁺ for simultaneous albumin and IgG depletion, respectively. The PHEMA cryogel was synthesized by free radical polymerization in the presence of the modified PGMA beads. The PHEMA and PHEMA/PGMA composite cryogels were characterized by swelling measurements and scanning electron microscopy (SEM). Protein depletion studies were carried out in a continuous experimental set-up in a stacked column. Albumin adsorption capacity of the PGMA-Cibacron Blue F3GA beads embedded PHEMA cryogel (PHEMA/PGMA-Cibacron Blue F3GA) was 342 mg/g and IgG adsorption capacity of the PGMA-IDA-Cu²⁺ beads embedded PHEMA cryogel (PHEMA/PGMA-IDA-Cu²⁺) was 257 mg/g. The composite cryogels depleted albumin and IgG from human serum with 89.4% and 93.6% efficiency, respectively. High desorption values (over 90% for both modified cryogels) were achieved with 0.05 M phosphate buffer containing1.0 M NaCl.     

Poly(hydroxyethyl methacrylate) nanobeads containing imidazole groups for removal of Cu(II) ions

Poly(hydroxyethyl methacrylate) (PHEMA) nanobeads with an average size of 300 nm in diameter and with a polydispersity index of 1.156 were produced by a surfactant free emulsion polymerization. Specific surface area of the PHEMA nanobeads was found to be 996 m²/g. Imidazole containing 3-(2-imidazoline-1-yl)propyl(triethoxysilane) (IMEO) was used as a metal-chelating ligand. IMEO was covalently attached to the nanobeads. PHEMA-IMEO nanobeads were used for the removal of copper(II) ions from aqueous solutions. To evaluate the degree of IMEO loading, the PHEMA nanobeads were subjected to Si analysis by using flame atomizer atomic absorption spectrometer and it was estimated as 973 µmol IMEO/g of polymer. The PHEMA nanobeads were characterized by transmission electron microscopy and fourier transform infrared spectroscopy. Adsorption equilibrium was achieved in about 8 min. The adsorption of Cu²⁺ ions onto the PHEMA nanobeads was negligible (0.2 mg/g). The IMEO attachment into the PHEMA nanobeads significantly increased the Cu²⁺ adsorption capacity (58 mg/g). Adsorption capacity of the PHEMA-IMEO nanobeads increased significantly with increasing concentration. The adsorption of Cu²⁺ ions increased with increasing pH and reached a plateau value at around pH 5.0. Competitive heavy metal adsorption from aqueous solutions containing Cu⁺, Cd²⁺, Pb²⁺ and Hg²⁺ was also investigated. The adsorption capacities are 61.4 mg/g (966.9 µmol/g) for Cu²⁺; 180.5 mg/g (899.8 µmol/g) for Hg²⁺; 34.9 mg/g (310.5 µmol/g) for Cd²⁺ and 14.3 mg/g (69 µmol/g) for Pb²⁺. The affinity order in molar basis is observed as Cu²⁺ > Hg²⁺ > Cd²⁺ > Pb²⁺. These results may be considered as an indication of higher specificity of the PHEMA-IMEO nanobeads for the Cu²⁺ comparing to other ions. Consecutive adsorption and elution operations showed the feasibility of repeated use for PHEMA-IMEO nanobeads.     

Purification of yeast alcohol dehydrogenase by using immobilized metal affinity cryogels

In this study, poly(2-hydroxyethyl methacrylate–glycidylmethacrylate) [poly(HEMA–GMA)] cryogels were prepared by radical cryocopolymerization of HEMA with GMA as a functional comonomer and N,N′-methylene-bisacrylamide (MBAAm) as a crosslinker. Iminodiacetic acid (IDA) functional groups were attached via ring opening of the epoxy group on the poly(HEMA–GMA) cryogels and then Zn(II) ions were chelated with these structures. Characterization of cryogels was performed by FTIR, SEM, EDX and swelling studies. These cryogels have interconnected pores of 30–50 μm size. The equilibrium swelling degree of Zn(II) chelated poly(HEMA–GMA)-IDA cryogels was approximately 600%. Zn(II) chelated poly(HEMA–GMA)-IDA cryogels were used in the adsorption of alcohol dehydrogenase from aqueous solutions and adsorption was performed in continuous system. The effects of pH, alcohol dehydrogenase concentration, temperature, and flow rate on adsorption were investigated. The maximum amount of alcohol dehydrogenase adsorption was determined to be 9.94 mg/g cryogel at 1.0 mg/mL alcohol dehydrogenase concentration and in acetate buffer at pH 5.0 with a flow rate of 0.5 mL/min. Desorption of adsorbed alcohol dehydrogenase was carried out by using 1.0 M NaCI at pH 8.0 phosphate buffer and desorption yield was found to be 93.5%. Additionally, these cryogels were used for purification of alcohol dehydrogenase from yeast with a single-step. The purity of desorbed alcohol dehydrogenase was shown by silver-stained SDS–PAGE. This purification process can successfully be used for the purification of alcohol dehydrogenase from unclarified yeast homogenates and this work is the first report about the usage of the cryogels for purification of alcohol dehydrogenase.     

Permeable,robust and magnetic hydrogel beads: water droplet templating synthesis and utilization for heavy metal ions removal

By comprehensively utilizing interfacial tension and ultrafast radical polymerization as driving forces, we reported here a water droplet templating polymerization strategy to synthesize dithiocarbamate-decorated poly(vinyl amine) hydrogel beads (DTC-Fe₃O₄@PVAM) adsorbent material for heavy metal ions removal. The polymerization-induced rapid gelation behavior, being monitored by optical tracer microrheology, was achieved by using reactive monomers and low activation energy initiator. With this method, the monodisperse and size-controlled millimeter-scale DTC-Fe₃O₄@PVAM beads could be produced in mass. Different from traditional interfacially cross-linked hydrogel beads, the homogeneous polymeric network skeleton containing stable C–N cross-linkages was generated, which could withstand harsh chemical conditions and showed good fatigue resistance. Furthermore, the formed highly permeable macroporous structure is beneficial for mass transfer process and contributes to rapid adsorption equilibriums. Owing to the introduction of chelating DTC groups and Fe₃O₄ nanofillers, the reported adsorbent material also exhibits considerable adsorption capacities, good foreign ions resistance, convenient magnetic separation and efficient reusability. This work might contribute to the improved design and novel preparation strategy of millimeter-scale hydrogel beads adsorbent materials for water environment remediation.     

Poly(hydroxyethyl methacrylate-co-methacryloylamidotryptophane) nanospheres and their utilization as affinity adsorbents for porcine pancreas lipase adsorption

Novel nanospheres with an average size of 350 nm utilizing N-methacryloyl-(l)-tryptophane methyl ester (MATrp) as a hydrophobic monomer were prepared by surfactant free emulsion polymerization of 2-hydroxyethyl methacrylate (HEMA), (MATrp) conducted in an aqueous dispersion medium. MATrp was synthesized using methacryloyl chloride and (l)-tryptophane methyl ester. Specific surface area of the non-porous nanospheres was found to be 1902.3 m²/g. poly(HEMA–MATrp) nanospheres were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM). Average particle size and size distribution measurements were also performed. Elemental analysis of MATrp for nitrogen was estimated at 1.36 mmol/g nanospheres. Then, poly(HEMA–MATrp) nanospheres were used in the adsorption of porcine pancreas lipase in a batch system. Using an optimized adsorption protocol, a very high loading of 558 mg enzyme/g nanospheres was obtained. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The K_m value for immobilized lipase (16.26 mM) was higher than that of free enzyme (10.34 mM). It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption amount or enzyme activity. These findings show considerable promise for this material as an adsorption matrix in industrial processes.