MoS2 nanoflowers decorated natural fiber-derived hollow carbon microtubes for boosting perfluorooctanoic acid degradation

Abstract

Calotropis gigantea fiber (CGF) is a natural cellulose fiber with thin-walled large lumen. Benefitted from its unique structure, CGF was utilized here as a bio-template for the fabrication of hollow carbon microtubes using a facile hydrothermal method, and simultaneously, nano-sized MoS2 flowers were in-situ generated along the inner and outside surfaces of carbonized fiber microtubes, forming MoS2 nanoflowers decorated biochar MoS2/CGB. Coupled with dual active centers from non-metallic biochar and metallic MoS2, MoS2/CGB was then used for activating peroxymonosulfate (PMS) to degrade perfluorooctanoic acid (PFOA), one emerging pollutant that had received wide attention in recent years. The experimental results indicated that at room temperature and pH 3.0, MoS2/CGB exhibited the degradation efficiency of 79.6% for PFOA, and removal percentage of 50.7% for total organic carbon. During the degradation process, the free radical (SO4•−/•OH) and non-radical (1O2) routes coexisted, and the amount of SO4•− was about 9 times that of •OH. Combined with mass spectrometry, the possible degradation pathway of PFOA was proposed as transforming into short chained C2- to C5-containing carboxylic acids. With Vibrio fischeri as an indicator, the acute toxicity of PFOA solution and intermediates was evaluated, with the inhibition rate decreased from 27.6% to 4.5%. Finally, MoS2/CGB had the ability not only for removing perfluorinated compounds with different carbon chain lengths, but also for catalytically degrading PFOA in tap water and Yellow River water. This work provides plant fiber-based sustainable catalyst for potential application in PMS-based system for boosting PFOA degradation.