Catalytic Reductive Degradation of 4-Nitrophenol and Methyl orange by Novel Cobalt Oxide Nanocomposites

Abstract

Cobalt oxide nanocomposites were synthesized and used for the catalytic degradation of 4-nitrophenol (4-NP) and methyl orange (MO). Cobalt oxide nanocomposites PyroHAB9 was prepared by heating cobalt acetylacetonate complex HAB9 at 300 °C, while PyroHAB19 was prepared by heating cobalt acetylacetonate–carboxymethyl cellulose complex at 300 °C. FTIR indicated the presence of Co3O4 species, while Raman spectrum indicated the presence of graphite in PyroHAB19. The SEM morphology of nanocomposites exhibited irregular spherical shape nanoparticles with sizes ranging between 20 to 60 nm. Additionally, nanowires were also seen in HAB19. Also, 2Ɵ peaks in PXRD revealed the formation of Co3O4 in HAB19. Cyclic voltammetry indicated enhanced electrochemical redox activity of HAB19. The structures of the nanocomposites were related to their catalytic activities. The turnover frequency (TOF) values of the catalytic reduction of p-nitrophenol (P-NP) and methyl orange (MO) were greater for HAB19 compared to HAB9 nano-catalysts. Also, the TOF values of the catalytic reduction of MO were greater than that of P-NP by both nano-catalysts. It is obvious that the rate constants of catalytic reductions for MO by metal oxide nanocomposites were greater than the corresponding rate constants for PNP. The highest rate constant was found for PyroHAB19 in MO reduction.