Dispersion of mixed metal oxides into polymeric matrix

Abstract

A mixed oxide of cobalt and nickel metals was prepared chemically by a double displacement reaction. The metal carbonate, as obtained from the reaction between ammonium carbonate and metal nitrates, was then calcined at 650 DC. The calcined product yielded the cobalt-nickel mixed oxide (MO). Similar process was also adopted to get the individual cobalt oxide and nickel oxide matrices. The dispersion of the mixed oxide in polyaniline (PANI) matrix was achieved by in-situ polymerization of aniline from a medium containing a oxidant potassium permanganate, H2S04 and suspension of the mixed oxide. The oxides and the mixed oxide disperse PANI matrices were characterized by a wide range of experimental techniques viz, EDX, UV- Visible and IR spectroscopy, X-ray diffraction, SEM and electrical conductance. Elemental analysis showed the presence of cobalt, nickel and oxygen elements in the mixed oxide with an average composition of COo.4Nio.40o.2. UV-Visible and IR spectroscopic studies yielded useful infOlmation on the structure of the matrices studied. The strong absorption maxima observed for PANI and PANI/MO at 309 nm is attributed to the inter band transition; the other absorption at 663 nm indicates a transition between the mid-gap states. IR spectral analysis of the samples yielded useful information on the identification of the compounds. From the spectra the band characteristics of cobalt oxide, nickel oxide, MO, PANI and PANI/MO confirmed the presence of the components in each substrate. X-ray scattering patterns of the oxides and MO oxide indicate the crystalline nature of the oxides. On the other hand, diffuse patterns of the PANI/MO matrix demonstrating its amorphous structure. Surface morphology obtained by SEM provides very interesting results. The surface of cobalt oxide and nickel oxide are granular and consist of the particles having sizes ranging from nm to ~m level. SEM observation for the MO surface seems to consist of agglomerates. Surface of PANI/MO shows fibrils spreading over the substrate where few agglomerates are also distributed indicating the presence of mixed oxide. Electrical conductivity of cobalt oxide, nickel oxide, MO, PANI and PANI/MO was measured by a two point-probe technique at room temperature. The conductivity ofPANI/MO was found to be higher than that of PANI and MO. However, the measured conductivities of studied matrices were in the range of 10,7 to 10,3 Scm'l. The PANI/MO was utilized as electrode modifier to study the Fe2+/ Fe3+ redox process. The oxidation and reduction processes of Fe2+/ Fe3+ system was successfully carried out on the modified PANI/MO electrode indicating the electrode activity of the PANI/MO matrix. In order to examine the surface capacity of the MO, adsorption of dyestuffs viz. methylene blue (MB) and procion red (PR) was attempted on the MO surface. The adsorption data showed that both the MB and PR dyes can be adsorbed on the mixed oxide surface. But the extent of PR adsorption is much higher than MB, suggesting the present MO a specific adsorbent for the PR removal. Photolysis of dyestuffs were also carried out. The extent of dye removal under photolysis was found to be nearly identical to that observed without photolysis, suggesting that the high surface performance of the MO is achievable without external force like photolysis.