title: Selective elimination of lead(II) ions by alginate/polyurethane composite foams.
abstract: A new type of adsorbent which is capable of selectively adsorbing lead(II) ions (Pb(2+)) was developed. The adsorbent was generated by reaction of sodium alginate with NB-9000B, a polyisocyanate type of prepolymer of polyurethane. The adsorbent was a hydrophilic and flexible alginate/polyurethane composite foam (ALG/PUCF) with the alginate chemically immobilized in the cell walls of the foam. Acid-base titration was used to quantify the concentration of carboxyl groups, which are present on the alginate molecules of the ALG/PUCF, functioning as the essential sites for binding Pb(2+). For the optimized ALG/PUCF, the carboxyl was found to be 38.2+/-1.2mumol/g of dry weight. The capacity for adsorbing Pb(2+) ions in 1.0g of dry weight of the optimized ALG/PUCF was found to be 16.0+/-2.1mumol, indicating that ion exchange was the essential mechanism for adsorbing Pb(2+) ions. The adsorption capacity was found to be highly sensitive to the pH of the sample solution; lower pH (<3) significantly decreased the adsorption. Competing ions such as Mg(2+), Ca(2+), and Cd(2+) also caused a decrease in selectivity and capacity for Pb(2+) adsorption, although the effect was less pronounced than the effect of pH. The ALG/PUCF is highly stable, flexible and easy to use. ALG/PUCF is also reusable after regeneration with ethylenediamine-N,N,N',N'-tetraacetic acid, disodium salt (EDTA-2Na). Due to these features, this adsorbent may be highly useful for elimination of Pb(2+) ions from contaminated water.
authors.affiliation: Laboratory of Environmental Remediation, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Sone
authors.forename: Bunshi
authors.initials: B
authors.lastname: Fugetsu
authors.forename: Shunitz
authors.initials: S
authors.lastname: Tanaka
mesh_terms: D000327:Adsorption; D000464:Alginates / Q000138:chemical synthesis / Q000737:chemistry*; D002240:Carbohydrate Sequence; D002614:Chelating Agents / Q000737:chemistry; D003432:Cross-Linking Reagents; D004492:Edetic Acid / Q000737:chemistry; D020100:Hydrogels; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007854:Lead / Q000737:chemistry* / Q000302:isolation & purification; D008670:Metals / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D011140:Polyurethanes / Q000138:chemical synthesis / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D000464:Alginates; D002614:Chelating Agents; D003432:Cross-Linking Reagents; D020100:Hydrogels; D007202:Indicators and Reagents; D008670:Metals; D011140:Polyurethanes; D007854:Lead; D004492:Edetic Acid