Performance of dye-affinity beads for aluminium removal in magnetically stabilized fluidized bed

BACKGROUND: Aluminum has recently been recognized as a causative agent in dialysis encephalopathy, osteodystrophy, and microcytic anemia occurring in patients with chronic renal failure who undergo long-term hemodialysis. Only a small amount of Al(III) in dialysis solutions may give rise to these disorders. METHODS: Magnetic poly(2-hydroxyethyl methacrylate) (mPHEMA) beads in the size range of 80–120 μm were produced by free radical co-polymerization of HEMA and ethylene dimethacrylate (EDMA) in the presence of magnetite particles (Fe(3)O(4)). Then, metal complexing ligand alizarin yellow was covalently attached onto mPHEMA beads. Alizarin yellow loading was 208 μmol/g. These beads were used for the removal of Al(III) ions from tap and dialysis water in a magnetically stabilized fluidized bed. RESULTS: Al(III) adsorption capacity of the beads decreased with an increase in the flow-rate. The maximum Al(III) adsorption was observed at pH 5.0. Comparison of batch and magnetically stabilized fluidized bed (MSFB) maximum capacities determined using Langmuir isotherms showed that dynamic capacity (17.5 mg/g) was somewhat higher than the batch capacity (11.8 mg/g). The dissociation constants for Al(III) were determined using the Langmuir isotherm equation to be 27.3 mM (MSFB) and 6.7 mM (batch system), indicating medium affinity, which was typical for pseudospecific affinity ligands. Al(III) ions could be repeatedly adsorbed and desorbed with these beads without noticeable loss in their Al(III) adsorption capacity. CONCLUSIONS: Adsorption of Al(III) demonstrate the affinity of magnetic dye-affinity beads. The MSFB experiments allowed us to conclude that this inexpensive sorbent system may be an important alternative to the existing adsorbents in the removal of aluminium

Removal of Heavy Metal Ions Using the Fungus

The potential use of the fungus Penicillium canescens for the removal of cadmium, lead, mercury and arsenic ions from aqueous solutions was evaluated in this study. Equilibrium biosorption of the heavy metal ions was attained in 4 h. The binding of heavy metal ions to P. canescens was clearly pH-dependent. Under acidic conditions, the heavy metal ion loading capacity increased with increasing pH, presumably as a result of heavy metal speciation and competition with hydrogen ions for the same binding sites. The adsorption of heavy metal ions attained a plateau value at ca. pH 5.0. The maximum adsorption capacities of the heavy metal ions studied onto the fungal biomass under non-competitive conditions were 26.4 mg/g for As(III), 54.8 mg/g for Hg(II), 102.7 mg/g for Cd(II) and 213.2 mg/g for Pb(II), respectively. The competitive adsorption capacities of the heavy metal ions were 2.0 mg/g for As(III), 5.8 mg/g for Hg(II), 11.7 mg/g for Cd(II) and 32.1 mg/g for Pb(II), respectively, at a 50-mg/l initial concentration of the metal ions. The same affinity order was observed under non-competitive and competitive adsorption conditions, i.e. Pb(II) > Cd(II) > Hg(II) > As(III). The equilibrium loading capacity of Pb(II) was greater than that of other metal ions, the fungal biomass showing preference towards the binding of Pb(II) over Cd(II), Hg(II) and As(III). Elution of heavy metal ions was performed using 0.5 M HCl. The fungus Penicillium canescens could be used for biosorption over six cycles

Heavy Metal Ion Adsorption Properties of Methacrylamidocysteine-Containing Porous Poly(Hydroxyethyl Methacrylate) Chelating Beads

Details of the adsorption performance of poly(2-hydroxyethylmethacrylate–methacrylamidocysteine) [p(HEMA–MAC)] beads towards the removal of heavy metal ions from aqueous solution were studied. The metal-complexing ligand and/or co-monomer MAC was newly synthesized from methylacrylochloride and cysteine. Spherical beads of average size 150–200 mm were obtained by the radical suspension polymerization of MAC and HEMA conducted in an aqueous dispersion. The p(HEMA–MAC) beads obtained had a specific surface area of 18.9 m 2 /g. p(HEMA–MAC) beads were characterized by swelling studies, FT-IR spectroscopy and elemental analysis. Such beads with a swelling ratio of 72%, and containing 3.9 mmol MAC/g, were used for heavy metal removal studies. The adsorption capacities of the beads for selected metal ions, i.e. Cd II , As III , Cr III , Hg II and Pb II , were investigated in aqueous media containing different amounts of these ions (10–750 mg/l) and at different pH values (3.0–7.0). The adsorption rate was fast in all cases. The maximum adsorption capacities of the p(HEMA–MAC) beads were 1058.2 mg/g for Cd II , 123.4 mg/g for As III , 199.6 mg/g for Cr III , 639.1 mg/g for Pb II and 1018.6 mg/g for Hg II . On a molar basis, the following affinity order was observed: Cd II > Hg II > Cr III > Pb II >As III . The adsorption capacity of the MAC-incorporated beads was affected significantly by the pH value of the aqueous medium. The adsorption of heavy metal ions from artificial wastewater was also studied. In this case, the adsorption capacities were 52.2 mg/g for Cd II , 23.1 mg/g for Cr III , 83.4 mg/g for Hg II , 62.6 mg/g for Pb II and 11.1 mg/g for As III at an initial metal ion concentration of 0.5 mmol/l. The chelating beads could be regenerated easily with a higher effectiveness by 0.1 M HNO 3 . These features make p(HEMA–MAC) beads potential candidates for heavy metal ion removal at high capacity

Highly selective ion-imprinted particles for solid-phase extraction of Pb2+ ions

WOS: 000271256700024The 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 mu m 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. (C) 2009 Elsevier B.V. All rights reserved

Bilirubin recognition via molecularly imprinted supermacroporous cryogels

Recent years molecular imprinting has received considerable attention as an excellent and simple approach to recognize small molecules and bioactive substances. The aim of this study is to prepare the bilirubin-imprinted supermacroporous cryogels which can be used for the adsorption of bilirubin from human plasma. N-methacryloyl(L)-tyrosinemethylester (MAT) was chosen as the preorganization monomer. In the first step, bilirubin was complexed with MAT and the bilirubin-imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-(L)-tyrosine methylester) [BR-MIP] cryogel was produced by free radical polymerization initiated by N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. After that, the template molecules (i.e., bilirubin) were removed from the polymeric structure using sodium carbonate and sodium hydroxide. The maximum bilirubin adsorption amount was 3.6 mg/g polymer. The relative selectivity coefficients of the BR-MIP cryogel for bilirubin/cholesterol and bilirubin/testosterone mixtures were 7.3 and 3.2 times greater than non-imprinted poly(HEMA-MAT) [NIP] cryogel, respectively. The BR-MIP cryogel could be used many times without decreasing bilirubin adsorption amount significantly. Therefore, as a reusable carrier possessing high selectivity, BR-MIP cryogel has a potential candidate as a clinical hemoperfusion material. (C) 2008 Elsevier B.V. All rights reserved

Protein recognition via ion-coordinated molecularly imprinted supermacroporous cryogels

Molecular imprinting is a method for making selective binding sites in synthetic polymers using a molecular template. The aim of this study is to prepare lysozyme-imprinted supermacroporous cryogels which can be used for the purification of lysozyme (Lyz) from egg white. N-Methacryloyl-(L)-histiclinemethylester (MAH) was chosen as the metal-coordinating monomer. In the first step, Cu2+ was complexed with MAH and the lysozyme-imprinted poly(HEMA-MAH) [Lyz-MIP] cryogel were produced by free radical polymerization initiated by N,N,N',N'-tetramethylene diamine (TEMED) in an ice bath. After that, the template (i.e., lysozyme) was removed using 0.05 M phosphate buffer containing 1 M NaCl (pH 8.0). The maximum lysozyme adsorption capacity was 22.9 mg/g polymer. The relative selectivity coefficients of Lyz-MIP cryogel for lysozyme/bovine serum albumin and lysozyme/cytochrome c were 4.6 and 3.2 times greater than non-imprinted poly(HEMA-MAH) (NIP) cryogel, 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 94% with recovery about 86%. The Lyz-MIP cryogel could be used many times without decreasing the adsorption capacity significantly

Supermacroporous poly(hydroxyethyl methacrylate) based cryogel with embedded bilirubin imprinted particles

Molecular imprinted polymers are artificial, template-made materials with the ability to recognize and to specifically bind the target molecule. The aim of this study is to prepare supermacroporous cryogel with embedded bilirubin-imprinted particles which can be used for the selective removal of bilirubin from human plasma. N-methacryloyl-(L)-tyrosinemethylester (MAT) was chosen as the pre-organization monomer. In the first step, bilirubin was complexed with MAT and the bilirubin-imprinted poly(hydroxyethyl methacrylate-N-methacryloly-(L)-tyrosine methyl-ester) [MIP] monolith was produced by bulk polymerization. MIP monolith was smashed and the particles ground and sieved through 100 pm sieves. In the second step. the supermacroporous poly(hydroxyethyl methacrylate) (PHEMA) cryogel with embedded MIP particles [PHEMA/MIP composite cryogel] was produced by free radical polymerization initiated by N.N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. After that, the template (i.e., bilirubin) molecules were removed using sodium carbonate and sodium hydroxide. Compared with the PHEMA cryogel (0.2 mg/g polymer), the bilirubin adsorption capacity of the PHEMA/MIP composite cryogel (10.3 mg/g polymer) was improved significantly due to the embedded MIP particles into the polymeric matrix. The relative selectivity coefficients of PHEMA/MIP composite cryogel for bilirubin/cholesterol and bilirubin/testosterone were 8.6 and 4.1 times greater than the PHEMA cryogel, respectively. The PHEMA/MIP composite cryogel could be used many times without decreasing the bilirubin adsorption capacity significantly. (c) 2008 Elsevier Ltd. All rights reserved