Adsorption of phosphoric acid on niobium oxide coated cellulose fiber: Preparation, characterization and ion exchange property

Abstract

The preparation procedures for a hybrid organic-inorganic cellulose-niobium oxide (Cel/Nb2O5) and its derivative, Cel/Nb 2O5/phosphate, are described. The precursor reagent of the metal oxide was the very convenient water soluble niobium oxalate compound, NH4[NbO(C2O4)2)(H2O) 2].nH2O. Phosphate ion was adsorbed on the Cel/Nb 2O5 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/H 2PO4- showed good affinity for retaining Na+, K+ and Ca2+ when in contact with these ions in an aqueous solution. ©2005 Sociedade Brasileira de Química.