Oily sludge derived carbons as peroxymonosulfate activators for removing aqueous organic pollutants: Performances and the key role of carbonyl groups in electron-transfer mechanism

Abstract

In this work, low-cost carbon-based materials were developed via a facile one-pot pyrolysis of oily sludge (OS) and used as catalysts to activate peroxymonosulfate (PMS) for removing aqueous recalcitrant pollutants. By adjusting the pyrolysis temperature, the optimized OS-derived carbocatalyst manifested good performance for PMS activation to abate diverse organic pollutants in water treatment. Particularly, an average removal rate of 0.87mol phenol per mol PMS per hour at a catalyst dosage of 0.2gL-1 is attained by the OS-derived carbocatalyst, higher than many other documented catalysts. A series of experimental evidences consolidated that organic pollutants were oxidized mainly via electron-transfer mechanism albeit the detection of singlet oxygen (1O2) from PMS activation driven by the OS-derived carbocatalyst. Specifically, the proportion of carbonyl groups (C˭O) in the carbocatalyst adopted with selective modification treatments to tailor the surface chemistry was found to be linearly correlated with the catalytic activity and theoretical calculations demonstrated that the reactions between C˭O and PMS to form surface reactive complexes were more energetically favorable compared to 1O2 generation. Herein, this study not only offers a new strategy for reusing OS as value-added persulfate activators but also deepens the fundamental understanding on the nonradical regime.