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

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 NaBH 4 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 NaBH 4 . The catalytic reaction has an induction period followed by an autoacceleration, which depends on the [NaBH 4 ]. The reaction follows fractional‐order kinetics with respect to [NaBH 4 ] 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: