title: Adsorption of As(III) and As(V) onto colloidal microparticles of commercial cross-linked polyallylamine (Sevelamer) from single and binary ion solutions.
abstract: This work investigates the removal of arsenic ions in trivalent (As(III)) or pentavalent form (As(V)) from single-component and binary (equal initial ion concentrations) aqueous solutions using commercial cross-linked polyallylamine (namely as Sevelamer) as adsorbent. This is the first work in literature regarding the application of that commercial material as adsorbent for ions. Sevelamer (SVL) is a widely known pharmaceutical compound and the existence of primary and secondary amino groups (with different ratios) in its molecule increases its adsorption potential. For this purpose can be easily proposed as potential sorbent. The adsorption evaluation was based on the pH-effect (optimum pH=6, where As(III) and As(V) removal was 69 and 86%, respectively), isotherms and kinetic curves. The maximum theoretical adsorption capacity (Qm) was 86 and 133mg/g for single-component solutions of As(III) and As(V), respectively. The respective values for binary mixtures of the same concentration (100mg/L) were 84 and 116mg/g, respectively (calculated after fitting to Langmuir-Freundlich isotherm model at 20°C). A novel kinetic interpretation based on the raw experimental kinetics data was also developed. Although adsorption of As(III) and As(V) occurs mainly at different sites, there is an interdependence in their adsorption kinetics. It was found that adsorption from the binary mixtures is a two-stage process. The adsorption mechanism of SVL and arsenic ions interaction was elucidated using FTIR spectroscopy before and after adsorption. SEM images and XRD patterns (the material was amorphous both before and after arsenic adsorption indicating that the mechanism did not alter its physical state) were also taken for the characterization of SVL before and after arsenic adsorption. The adsorption mechanism was mainly attributed to the electrostatic interactions between negatively As ions and positively charged amino groups of SVL. For this reason, As(V) adsorption is higher than As(III).
authors.affiliation: Division of Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece.
authors.forename: George Z
authors.initials: GZ
authors.lastname: Kyzas
authors.affiliation: Division of Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece.
authors.forename: Panoraia I
authors.initials: PI
authors.lastname: Siafaka
authors.affiliation: Division of Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece.
authors.forename: Margaritis
authors.initials: M
authors.lastname: Kostoglou
authors.affiliation: Division of Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece. Electronic address: dbic@chem.auth.gr.
authors.forename: Dimitrios N
authors.initials: DN
authors.lastname: Bikiaris
keywords: Adsorption; Arsenate; Arsenite; Characterizations; Kinetic modeling; Sevelamer