In-situ sulfur-doped carbon as a metal-free catalyst for persulfate activated oxidation of aqueous organics

In-situ S-doped activated carbons with huge specific surface areas and developed total pore volumes were prepared by chemical activation of polythiophene with KOH as activator under different annealing temperatures (from 600 to 800 degrees C). The obtained material treated at 800 degrees C (ACS-800) showed the best catalytic activity for 4-chlorophenol (4CP) oxidation. Almost 100% 4CP removal was attained for ACS-800 in 60 min with an apparent rate constant of 0.083 min(-1), which was much higher than that of S-free activated carbon (0.032 min(-1)). N-2 sorption isotherms and XPS spectra indicated that the sulfur doping and the removal of acidic functional groups (such as sulphone groups and carboxyl groups) at high temperature strongly enhanced the catalytic activity of ACS-800. In comparison experiments, ACS-800 presented superior performance in PS activation to conventional catalysis techniques (Co3O4, Fe3O4, zero-valent iron (ZVI), reduced graphene oxide (rGO), and multi-walled carbon nanotube (MWCNT)). Moreover, different peroxides and various aqueous organics were used to further evaluate the catalytic activity of ACS-800. Results showed that ACS-800 could activate various peroxides and degrade different kinds of contaminants. The high catalytic activity and general applicability of ACS-800 make it to be a promising metal-free catalyst for environmental remediation.