Preventing re-emission of malodorous dimethylamine via tunable nonradical oxidation catalyzed by waste mask-derived carbocatalyst

Abstract

The re-emission of dimethylamine (DMA), as a famous malodorous volatile organic compound (VOC), exhausted from various industries receives emerging concerns. Herein, a metal-free carbocatalyst derived from waste masks was developed to inhibit DMA re-emission via activating peroxymonosulfate (PMS). The optimal inhibition efficiency was around 99%, 85-fold higher than that without any carbocatalysts and PMS. Such enhancement was ascribed to the rapid conversion of DMA (kobs = 0.67 min−1, 4 min) into non-volatile and lower toxic substances (NO3−, NO2− and aliphatic acids) by electron transfer and singlet oxygenation. Experiments combined with correlation analysis and theoretical calculations unveiled that the intensified graphitization degree promoted the electron migration from DMA to the carbocatalyst/PMS* complex due to the enhanced electron transfer rate and elevated redox potential, and PMS preferentially absorbed on the electron-rich C=O and deprotonated COO− groups rather than C-OH and COOH of carbocatalyst and then released SO5− for the generation of 1O2. Based on the theory, tuning the graphitization degree and amount of C=O and COO− groups via a simple annealing strategy triggered a shift from singlet oxygenation to predominantly direct electron transfer pathway, thus achieving optimal suppression efficiency of DMA re-emission. Finally, electrical energy per order (EE/O) analysis demonstrated our technology had a relatively low EE/O value (3.56 kWh/m3) and cost (0.47 $/m3). Considering the high efficiency and low cost of carbocatalytic PMS system endowed with clear mechanism and controllable properties, this work, therefore, pioneers an unparalleled approach for the industrial governance of effluvial VOCs treatment, and provides new insights into the tunable nonradical oxidation mechanism of carbocatalytic PMS activation.