Synthesis of Nitrogen-doped Carbon Nanotubes and the Performance and Mechanism of PMS Activation

Using multi-wall carbon nanotubes(MWCNT) as raw materials and melamine as a nitrogen precursor, a nitrogen-doped carbon nanotube (N-CNT-700) with a nitrogen content of about 3.33% (molar fraction) was prepared by high-temperature calcination. N-CNT-700 is a one-dimensional tubular nanomaterial, the degradation efficiency of phenol can reach 100%, and the total organic carbon (TOC) removal rate can reach 61.6%, and the activation energy of the system is 35.4 kJ/mol within 60 min in N-CNT-700 activated PMS system. Through electron paramagnetic resonance (EPR) detection, quenching experiment and PMS concentration determination, the degradation mechanism of the system was determined to be free radicals (center dot OH, SQ(4)(center dot-)) and non-free radicals, in addition to 9% adsorption removal, in the 91% oxidative degradation, free radicals account for about 49%, O-1(2) for about 18%, and active intermediates for about 24%. The reactivity of N-CNT700 decreases as the number of reuses increases, and high temperature treatment can restore its high reactivity. The calcination temperature affects the nitrogen content and types of the material. The reactivity of N-CNT is proportional to the nitrogen content and is closely related to the nitrogen content of graphite.