Abstract

PAVAN, Flávio A.; FRANCISCO, Maria Suzana P.; LANDERS, Richard  and  GUSHIKEM, Yoshitaka. Adsorption of phosphoric acid on niobium oxide coated cellulose fiber: preparation, characterization and ion exchange property. J. Braz. Chem. Soc. [online]. 2005, vol.16, n.4, pp. 815-820. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532005000500021.

The preparation procedures for a hybrid organic-inorganic cellulose-niobium oxide (Cel/Nb₂O₅) and its derivative, Cel/Nb₂O₅/phosphate, are described. The precursor reagent of the metal oxide was the very convenient water soluble niobium oxalate compound, NH₄[NbO(C₂O₄)₂)(H ₂O)₂].nH₂ O. Phosphate ion was adsorbed on the Cel/Nb₂O₅ by immersing this solid in an aqueous solution of phosphoric acid. Textural analyses carried out by using scanning electron microscopy (SEM) connected to an energy dispersive detector (EDS) revealed that the niobium oxide particles are, within the magnification used, uniformly dispersed on the cellulose matrix surface. Phosphoric acid is adsorbed on the material surface through the Nb-O-P linkage. The X-ray photoelectron and ³¹P NMR spectra showed that the adsorbed phosphate on the surface is the (H₂PO₄)^- species. The ion exchange isotherms obtained using the material Cel/Nb₂O₅/H₂PO₄^- showed good affinity for retaining Na⁺, K⁺ and Ca²⁺ when in contact with these ions in an aqueous solution.

Keywords : cellulose; niobium oxide; hybrid cellulose-niobium oxide; hybrid cellulose-niobium oxide-phosphate; ion exchange.