Using "waste" cotton-derived cellulose with different crystal structures to prepare nitrogen-doped carbon catalysts for activating peroxymonosulfate (PMS) to degrade Reactive Blue 19 "waste" water

Peroxymonosulfate (PMS) activated by nitrogen-doped carbon catalysts shows outstanding performance in wastewater treatment. Using cotton fibers with four crystalline structures from waste cotton as the carbon source and low-cost urea as the nitrogen source, four nitrogen-doped carbon catalysts (CU-I, CU-II, CU-III, and CU-IV) were prepared via carbonization and applied to activate PMS for degrading Reactive Blue 19 in wastewater. The results proved cotton fiber III as the preferred crystal structure. Within 40 min, the degradation efficiency of CU-III/PMS on Reactive Blue 19 reached 99%. Furthermore, CU-III exhibited an excellent degradation efficiency in a wide pH range from 3 to 11. After four degradation cycles, the degradation rate could still reach about 60%. The existence of center dot OH, SO4cent years, advanced o, 1O2, and O2 center dot- reactive oxygen species (ROS) in the CU-III/PMS system was confirmed by radical quenching experiments and electron paramagnetic resonance spectroscopy, which proved 1O2 as the main ROS. Non-radical electron transfer processes were also involved in the degradation. The active sites (pyridine nitrogen, pyrrolic nitrogen, and C=C species) of the nitrogen-doped carbon catalysts played vital roles in PMS activation. The toxicity experiments of high-concentration ions and degradation experiments of different dyes demonstrated the promise of the CU-III/PMS system in treating wastewater with various dye pollutants. In general, the prepared catalysts provide a new idea for both waste cotton recycling and wastewater treatment.