Kinetics and mechanism of organic pollutants degradation with cobalt–bicarbonate–hydrogen peroxide system: Investigation of the role of substrates

Abstract The kinetics and mechanism of a simple system, Co 2+ –HCO 3 − –H 2 O 2 for degrading highly stable organic pollutants have been reported. Fast and versatile decolorization of organic dyes was observed in an aqueous solution containing 10 mM NaHCO 3 , 10 μM Co 2+ ions and 10 mM H 2 O 2 , while the degradation rate of p-nitrophenol and 2,4-dinitrophenol was very slow. From cyclic voltammetry and UV–vis spectra, it was found that different complexes between Co 2+ ions and methylene blue (MB) were formed in HCO 3 − solution, and being confirmed by photoluminescence probing and electron spin resonance spin-trapping technologies, the 1:1 complex [Co II (HCO 3 − )(MB)] + was more efficient in catalyzing decomposition of H 2 O 2 into OH radicals. The other tested pollutants also played an important role in the rate of OH radicals production in the system. Based on the kinetic observations of MB decolorization, a possible mechanism was proposed.