title: Equilibrium and kinetics studies of arsenate adsorption by FePO(4).
abstract: The present work is focusing on removal of arsenate from aqueous solution using FePO4. The equilibrium study regarding the removal of arsenic by FePO4 was carried out at 298, 308, 318 and 328K. Langmuir parameters were found to increase with the increase in temperature indicating that the adsorption is favorable at high temperature. Kinetic study of arsenate adsorption on FePO4 was also carried out at different temperatures and at pH 6 and 8. Different kinetic models were used to the kinetic data amongst which pseudo second order model was best fitted. The mechanism of the adsorption kinetics was investigated by employing intraparticle diffusion and Richenberg models. The energy of activation (Ea) was found to be 30 and 35.52kJmol(-1) at pH 6 and pH 8, respectively, suggesting chemisorption nature of the adsorption process. The negative entropic values of activation signified the existence of entropy barrier while the positive ΔG(#) values indicated the existence of energy barrier to be crossed over for the occurrence of a chemical reaction. Both the spectroscopic studies and increase in equilibrium pH reveal the anion exchange removal of arsenate from aqueous solution to the solid surface.
authors.affiliation: National Centre of Excellence in Physical Chemistry, University of Peshawar, 25120 Peshawar, Pakistan.
authors.forename: M
authors.initials: M
authors.lastname: Hamayun
authors.affiliation: National Centre of Excellence in Physical Chemistry, University of Peshawar, 25120 Peshawar, Pakistan.
authors.forename: T
authors.initials: T
authors.lastname: Mahmood
authors.affiliation: National Centre of Excellence in Physical Chemistry, University of Peshawar, 25120 Peshawar, Pakistan. Electronic address: naeeem64@yahoo.com.
authors.forename: A
authors.initials: A
authors.lastname: Naeem
authors.affiliation: National Centre of Excellence in Physical Chemistry, University of Peshawar, 25120 Peshawar, Pakistan.
authors.forename: M
authors.initials: M
authors.lastname: Muska
authors.affiliation: National Centre of Excellence in Physical Chemistry, University of Peshawar, 25120 Peshawar, Pakistan.
authors.forename: S U
authors.initials: SU
authors.lastname: Din
authors.affiliation: National Centre of Excellence in Physical Chemistry, University of Peshawar, 25120 Peshawar, Pakistan.
authors.forename: M
authors.initials: M
authors.lastname: Waseem
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000737:chemistry*; D001151:Arsenic / Q000737:chemistry; D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D010710:Phosphates / Q000737:chemistry*; D013696:Temperature
chemical_list: D001149:Arsenates; D010710:Phosphates; D007501:Iron; D001151:Arsenic; C025657:arsenic acid
keywords: Adsorption; Arsenic; Ferric phosphate; Kinetics; Sorption maxima