Catalytic Activity of Cobalt Nanoparticles for Dye and 4-Nitro Phenol Degradation: A Kinetic and Mechanistic Study

Abstract

Cetyltrimethylammonium bromide (CTAB) capped nanosized α-cobalt hydroxides (CoNPs) were prepared to the removal of Congo red at room temperature in the absence and presence of sunlight. UV/visible spectra reveal that the CoNPs and NaBH4 have no catalytic effects toward Congo red and 4-nitrophenol (4-NP) degradation, whereas CoNPs act as an efficient catalyst with a small amount of NaBH4. The catalytic reaction has an induction period followed by an autoacceleration, which depends on the [NaBH4]. The reaction follows fractional-order kinetics with respect to [NaBH4] for Congo red degradation. The activation energies were found to be 24 and 74 kJ mol−1, respectively, for Congo red and 4-NP catalyzed reactions. The AgNPs has no catalytic activity toward Congo red. The degradation pathway mechanism with observed kinetics has been proposed and discussed, which follows the following rate law:. (Formula presented.).