Synthesis and characterization of polyaniline-titanium tungstophosphate; Its analytical applications for sorption of Cs+, Co2+, and Eu3+ from waste solutions

Abstract

Crystalline phases of polyaniline-titanium tungstophosphate composite material were synthesized via sol-gel procedure by incorporating the organic polymer polyaniline into the matrix of an inorganic precipitate of titanium tungstophosphate. The physicochemical properties of this hybrid material were determined using atomic absorption spectrophotometry, CHN elemental analysis, X-ray diffraction and X-ray fluorescence analysis, IR spectroscopy, thermal analysis, and scanning electron microscopy. According to the data obtained, the chemical formula of polyaniline-titanium tungstophosphate can be presented as [(WO3)(TiO2)4(H3PO4)3 + (-C6H4NH-)]·8H2O. The material shows monofunctional ion-exchange characteristic and exhibits enhanced resistance to HNO3, HCl, and alkaline media. The ion-exchange capacity of polyaniline-titanium tungstophosphate for Cs+, Co2+, and Eu3+ ions was found to be 3.63, 1.55, and 1.30 mg-equiv g−1, respectively, exceeding the ion-exchange capacity of other composite and inorganic ion exchangers. The material was found to be highly selective to Eu3+, with the following selectivity series: Eu3+ > Cs+ > Co2+. The thermodynamic functions (ΔG0, ΔS0, and ΔH0) of the adsorption of Cs+, Co2+, and Eu3+ ions onto polyaniline-titanium tungstophosphate were calculated. They show that the overall adsorption process is spontaneous and endothermic.