Modeling the heterogeneous peroxymonosulfate/Co-MCM41 process for the degradation of caffeine and the study of influence of cobalt sources

• Co-MCM41/PMS exhibited effective efficiency with low metal leaching.
• Effects of cobalt sources in Co-MCM-41 for the caffeine decay were identified.
• An operational model was established to predict the caffeine decay in Co-MCM41/PMS.

The potential of using cobalt incorporated MCM41 (i.e. Co-MCM41) prepared from different cobalt sources to activate peroxymonosulfate (PMS) for the degradation of caffeine in aqueous solution was evaluated. Experimental results showed that the Co-MCM41/PMS process could effectively degrade caffeine with a very low cobalt leaching (<5%) for the catalyst preparing from different cobalt sources. Cobalt was found being incorporated into the structure of MCM41 and resided within the crystal cell as cobalt cation, which play a critical role in dominating caffeine decay (via radical oxidation). Inhibiting effects of chloride and bicarbonate ions indicated that the sulfate radical was the key/active species for caffeine degradation. The inhibiting mechanism of phosphate on the same process, however, was mainly due to the complexation reaction between phosphate and cobalt cation in the structure of Co-MCM41. A series of kinetic experiments on CAF decay and the simultaneous PMS consumption were investigated. A mathematically operational model was therefore developed and verified to be capable of predicting the CAF decay successfully at various reaction conditions.