Oxidation of phenol by persulfate activated by zero-valent iron-biochar composites

Abstract

Zero-valent iron [Fe(0)]-biochar composites, namely, Fe(0)-included biochar and biochar-coated Fe(0), were synthesized and their catalytic performance in the activation of persulfate for phenol degradation in water was evaluated. In the presence of the Fe(0)-biochar composites, Fe(0)-included biochar-persulfate and biochar-coated Fe(0)-persulfate systems showed higher phenol removal than a Fe(0)-persulfate system by 11.6% and 20.7%, respectively. The difference in phenol removal by persulfate between Fe(0)-included biochar and biochar-coated Fe(0) was because of the high surface area of and oxygen-containing surface functional groups on the biochar coating of the latter. Differences in the properties of these two composites may also be responsible for the different optimal persulfate concentrations and doses of the composites required in the Fe(0)-included biochar-persulfate and biochar-coated Fe(0)-persulfate systems. Under optimal conditions, phenol degradation in the aqueous phase exceeded 95% for both composites. Electron paramagnetic resonance analysis revealed that hydroxyl and sulfate radicals were formed in the Fe(0)-biochar composite-persulfate systems. The results of this study suggest that Fe(0)-biochar composites can enhance phenol degradation by persulfate in water.