Activation of peroxymonosulfate for rhodamine-B removal from water: enhanced efficiency with cobalt-enriched, magnetically recoverable CNTs

Abstract

Dyes are known to pose environmental threats due to their mutagenic and persistent effects. To address this concern, researchers have explored various unconventional dye degradation materials, such as metal oxides with carbon materials. However, challenges related to degradation efficiency and regeneration have been significant obstacles. Consequently, there has been a surge in interest in recent years toward using nanomaterials with carbon materials activated by peroxymonosulfate for organic pollutant degradation. In this study, we present a novel approach to prepare a hybrid nanocomposite catalyst, CoS/CoFe₂O₄-CNTs (CS/CF-CNTs), using a carbon nanotube decorated with cobalt ferrite and further enhanced by embedding with cobalt sulfide nanoflowers. This catalyst aims at enhancing Rhodamine-B degradation through advanced oxidation processes. The carbon nanotubes provide a stable substrate for the cobalt materials, with cobalt ferrite (CF) serving as a magnetic component, facilitating catalyst removal and regeneration for multiple uses. Due to the oxidation involved in the degradation process, high electronic conductivity of the carbon nanotubes and the active cobalt sites of the composite play a crucial role in activating peroxymonosulfate to generate reactive oxygen radicals. Notably, the CS/CF-CNTs catalyst showed a remarkable Rhodamine-B degradation rate of 98% in less than 10 min. The catalyst also exhibited excellent stability even after four cycles of regeneration. The operating reaction conditions were optimized by investigating the effects of pH, dye concentration, salinity with different salts, catalyst dose, and peroxymonosulfate dose, and the results demonstrated the superior effectiveness of CS/CF-CNTs compared to CS and to CF-CNTs, emphasizing the synergistic interaction between the carbon nanotubes and the two cobalt materials. Quenching experiments revealed the involvement of sulfate and hydroxyl radicals in the degradation reaction mechanism.