Catalytic ozonation for imazapic degradation over kelp-derived biochar: Promotional role of N- and S-based active sites

It is a feasible strategy to prepare reliable biochar catalysts for heterogeneous catalytic ozonation (HCO) processes by using inexpensive, high quality, and easily available raw materials. Here, an environmentally friendly, simple, and green biochar catalyst rich in nitrogen (N) and sulfur (S) has been prepared by the pyrolysis of kelp. Compared with directly carbonized kelp biomass (KB), acid-activated KB (KBA) and base-activated KB (KBB) have higher specific sur-face areas and more extensive porous structures, although only KBB displays effective ozone activation. Imazapic (IMZC), a refractory organic herbicide, was chosen as the target pollutant, which has apparently not hitherto been investigated in the HCO process. Second-order rate constants (k) for the reactions of IMZC with three different reactive oxygen species (ROS), specifically kO3, IMZC, k center dot OH, IMZC, and k1O2, IMZC, have been determined as 0.974, 2.48 x 109, and 6.23 x 105 M-1 s-1, respectively. The amounts of graphitic N and thiophene S derived from the intrinsic N and S showed good correlations with the IMZC degradation rate, implicating them as the main active sites. center dot OH and center dot O2- and 1O2 were identified as main ROS in heterogeneous catalytic ozonation system for IMZC degradation. This study exemplified the utilization of endogenous N and Sin biological carbon, and provided more options for the application of advanced oxidation processes and the development of marine resources.

Automated summary

It is feasible to prepare reliable biochar catalysts for heterogeneous catalytic ozonation processes using inexpensive, high-quality, and easily available raw materials. A biochar catalyst rich in nitrogen and sulfur was prepared by pyrolyzing kelp. Acid-activated and base-activated kelp biochars had higher surface areas and more extensive porous structures, with base-activated biochar displaying effective ozone activation.