Sulfur and nitrogen co-doped biochar activated persulfate to degrade phenolic wastewater: Changes in impedance

In this research, sulfur and nitrogen co-doped biochar was prepared by co-pyrolysis method. The degradation law of phenol in simulated wastewater by activated potassium persulfate(PDS) was studied, and the effects of preparation conditions on the purification performance of phenol were also discussed. The results show that the phenol degradation rate by biochar with a doping ratio of 20% to activate PDS is up to 98.5%. In addition, the cycle performance of the doped biochar can still maintain 76% at the fifth cycle, indicating a good recycling performance. The results of density functional theory(DFT) calculations and various characterization techniques show that the sulfur and nitrogen exist in the form of thiophene sulfur and graphite nitrogen in the biochar, respectively. The electron density distribution of doped biochar become uneven, and the electrochemical impedance decreases from 32.88 to 10.53, prompting the reaction to proceed via non-radical path. Finally, the purification experiment results reveal that the S,NBC/PDS system possesses an excellent purification effect on simulated coal gasification wastewater, providing a reference for the industrial phenolic wastewater treatment.