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• Novel nitrogen-doped carbon fiber aerogel (N-CFA) was obtained by carbonization of cotton and urea in one-step. • 1O 2 instead of radicals was the predominant reactive oxidant species in N-CFA/PMS process. • CBZ degradation pathways mainly by 1O 2 were firstly proposed. • CBZ was removed in different water matrices with a satisfactory efficiency in N-CFA/PMS process. Nitrogen-doped carbon as metal-free catalysts exhibited exceptionally catalytic activities in environmental remediation fields. Herein, a novel nitrogen-doped carbon fiber aerogel (N-CFA), which was conveniently prepared using cotton and urea by a direct high temperature carbonization in one-step, was used to activate peroxymonosulfate (PMS) for the degradation of carbamazepine (CBZ) in water. Characterization results demonstrated that the key active sites (pyridinic N, pyrrolic N, and graphitic N) were formed in the process of nitrogen doping into the carbon fiber aerogel. More importantly, singlet oxygen (1O 2) instead of conventional OH and SO 4 − was suggested as the predominant reactive oxygen species (ROS) during N-CFA/PMS process based on the scavenger inhibition tests, and confirmed by molecular probe and liquid-phase electron paramagnetic resonance (EPR) experiments. It was speculated that nitrogen-containing functional groups played a key role in inducing the non-radical pathway. Moreover, CBZ degradation pathways mainly by 1O 2 were firstly proposed based on intermediates. The N-CFA/PMS system could achieve a CBZ degradation rate of 100% within 50 min, which was significantly higher than the catalytic effect of several carbon materials (ACF, GAC, and GO) and even higher than the catalytic effect of various metal-based catalysts including Co 3 O 4 , CuO, Fe 3 O 4 , and Fe 2 O 3. It was also noted that the CBZ was removed with a satisfactory efficiency in different water matrices with inorganic anions (HCO 3 –, Cl−, H 2 PO 4 −, SO 4 2−, and NO 3 –) and humic acid (HA). Thus, this study proposed a benign and highly efficient oxidation technology, which would exhibit wide potential for environmental restoration. [ABSTRACT FROM AUTHOR]