Adsorption of phosphate ions on novel inorganic ion exchangers

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• 作者：Chubar ; N.I. ; Kanibolotskyy ; V.A. ; Strelko ; V.V. ; Gallios ; G.G. ; Samanidou ; V.F. ; Shaposhnikova ; T.O. ; et. al.
• 关键词：Inorganic ion exchangers ; Adsorption ; Phosphate anions
• 刊名：Colloids and Surfaces A: Physicochemical and Engineering Aspects
• 出版年：2005
• 出版时间：March 21, 2005
• 年：2005
• 卷：255
• 期：1-3
• 页码：55-63
• 全文大小：314 K

文摘

The demand for cost effective adsorbents is widespread recognition through drinking water–liquid wastes treatment technologies. The novel ion exchangers based on individual and mixed hydrous oxides (ZrO₂·xH₂O, Fe₂O₃·Al₂O₃·xH₂O and Fe₂O₃·2Al₂O₃·xH₂O) have been obtained by sol–gel method from easily available and cheap raw materials and employed for adsorption of H₂PO₄⁻ from aqueous systems. High specific surface area of the materials was found: 404, 396 and 388m²g⁻¹ for ZrO₂·xH₂O, Fe₂O₃·Al₂O₃·xH₂O and Fe₂O₃·2Al₂O₃·xH₂O correspondingly. Adsorbents were characterized by potentiometric titration (anion exchange and cation exchange capacities (on H and OH⁻ ions)), zeta-potential and pore volume studies. pH effect of phosphate ions sorption on the double hydroxides of Fe and Al was stronger than on the hydrated zirconium dioxide, however, all investigated sorbents are capable to work in the pH range from 3 to 10 having sufficient sorption capacity. Increasing the ionic strength of the solutions with adding electrolyte NaCl increased sorption of phosphate ions on ZrO₂·xH₂O. The presence of Ca²⁺ in the solution increased sorption capacity at the higher equilibrium concentration of phosphate ions >40mgPl⁻¹. Isotherms of the phosphate ions sorption on Fe₂O₃·Al₂O₃·xH₂O and Fe₂O₃·2Al₂O₃·xH₂O were obtained at the pHs 3, 6 and 9. Isotherms fitted the Langmuir model. Data on the kinetics of phosphate sorption fit well to the pseudo-second-order model. It is supposed that mechanism of phosphate ions adsorption onto individual oxides hydrated is not only ion exchange between P(V) ions and hydroxide groups, present on the surface, but it is also a result of nucleophylic S_N2-i-replacement of OH groups via formation of intermediate six-centered complex with the release of water molecules.