Development of a Co2+/PMS process involving target contaminant degradation and PMS decomposition

The use of cobalt (II) salts (Co2+) for the catalytic decomposition of peroxymonosulfate (PMS) and the subsequent production of free radicals has demonstrated high efficiency in removing organic contaminants from water. However, only a few reports are available on the systematic analysis of PMS decomposition by Co2+ and its effect on contaminant degradation kinetics. In this study, PMS decomposition was evaluated at different initial PMS (5, 10, and 15 mM) and cobalt (0.05, 0.10, and 0.20 mM) concentrations. For all of the cases in this study, over 60% PMS decomposition was achieved after 30 min. A general degradation mechanism for any contaminant was proposed, as well as a kinetic model that incorporates the PMS/contaminant molar ratio. To validate the kinetic model, acetaminophen (ACT) was used as a target contaminant along with a response surface methodology (RSM) statistical analysis. Once validated, the model was used to determine ACT degradation by the Co2+/PMS process, the chemical oxygen demand (COD), and carboxylic acid evolution using the best experimental conditions.