title: Adsorptive features of polyacrylamide-apatite composite for Pb2+, UO(2)2+ and Th4+.
abstract: Micro-composite of polyacrylamide (PAA) and apatite (Apt) was prepared by direct polymerization of acrylamide in a suspension of Apt and characterized by means of FT-IR, XRD, SEM and BET analysis. The adsorptive features of PAA-Apt and Apt were then investigated for Pb(2+), UO(2)(2+) and Th(4+) in view of dependency on ion concentration, temperature, kinetics, ion selectivity and reusability. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. Apt in PAA-Apt had higher adsorption capacity (0.81, 1.27 and 0.69 mol kg(-1)) than bare Apt (0.28, 0.41 and 1.33 mol kg(-1)) for Pb(2+) and Th(4+), but not for UO(2)(2+). The affinity to PAA-Apt increased for Pb(2+) and UO(2)(2+) but not changed for Th(4+). The values of enthalpy and entropy changed were positive for all ions for both Apt and PAA-Apt. Free enthalpy change was DeltaG<0. Well compatibility of adsorption kinetics to the pseudo-second-order model predicated that the rate-controlling step was a chemical sorption. This was consistent with the free energy values derived from DR model. The reusability tests for Pb(2+) for five uses proved that the composite was reusable to provide a mean adsorption of 53.2+/-0.7% from 4x10(-3)M Pb(2+) solution and complete recovery of the adsorbed ion was possible (98+/-1%). The results of this investigation suggested that the use of Apt in the micro-composite form with PAA significantly enhanced the adsorptive features of Apt.
authors.affiliation: Cumhuriyet University, Department of Chemistry, Sivas 58140, Turkey. ulusoy@cumhuriyet.edu.tr
authors.forename: Ulvi
authors.initials: U
authors.lastname: Ulusoy
authors.forename: Recep
authors.initials: R
authors.lastname: Akkaya
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000327:Adsorption; D001031:Apatites / Q000737:chemistry*; D002412:Cations; D003188:Composite Resins / Q000737:chemistry*; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D013910:Thorium / Q000737:chemistry*; D017974:Uranium Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D001031:Apatites; D002412:Cations; D003188:Composite Resins; D007854:Lead; D013910:Thorium; D017974:Uranium Compounds; D000099166:Polyacrylamides; C012597:uranium dioxide