Adsorption Properties of Vermiculite with —Immobilized Polyaniline with Respect to Cr(VI), Mo(VI), W(VI), V(V) and P(V) Anions

Abstract

Immobilization of a polyaniline (PANI) on a natural vermiculite surface immediately after polymer formation ( in situ immobilization) has been performed. The adsorption properties of the modified adsorbent with respect to Cr(VI), Mo(VI), W(VI), V(V) and P(V) anions were studied. We found differences in physicochemical properties of clay samples using isotherms of nitrogen adsorption, X-ray diffraction and Fourier transform infrared spectroscopy. The experiments showed intercalation of PANI molecules into the inter-layer space of vermiculite. Adsorption isotherms and kinetics of adsorption were measured for the anionic form of ‘d’ metals of Groups V and VI in the Periodic Table from aqueous solutions by the static method. The results indicated that the synthesized composite had a high adsorption capacity with respect to Cr(VI) and Mo(VI) anions in acidic medium through the formation of dichromate anions (Cr 2 O 7 2– ) and an equilibrium mixture of molybdate (MoO 4 2– ) and polymolybdates ([Mo 6 O 21 ] 6– [Mo 7 O 24 ] 6– ). The modified adsorbent effected the quantitative removal of W(VI) anions in the whole pH range (pH = 1–9). The kinetic data showed that the adsorbent quantitatively removes chromium and molybdenum ions from solution in 1 hour.