Acceleration of goethite-catalyzed Fenton-like oxidation of ofloxacin by biochar.

While carbon materials have been well studied to stimulate the homogeneous Fenton-like processes, little was known about their impacts on iron mineral-catalyzed heterogeneous Fenton-like reactions. Here, it was found that biochar prepared at 300 °C or 600 °C (BC300 or BC600) greatly stimulated the degradation of ofloxacin (OFX) in a goethite (Gt)-mediated Fenton-like system. In 4 h, while only 38.4 % and 48.4 % OFX were removed in Gt/H2O2 and BC600/H2O2 systems, the removal efficiency reached over 94.0 % in Gt/BC600/H2O2 system. And the pseudo-first-order rate constant of Gt/H2O2, BC600/H2O2 and Gt/BC600/H2O2 systems were 0.12, 0.16 and 0.72 h-1, respectively, indicating the occurrence of synergistically catalytic degradation. •OH was identified as the major oxidant. Both the •OH yield and the H2O2 utilization efficiency of Gt/BC600/H2O2 system were higher than those of Gt/H2O2 and BC600/H2O2 systems. BC600 showed better stimulation effects than BC300. The persistent free radicals (PFRs) of BC could activate H2O2 and partly contribute to •OH production in the Gt/BC/H2O2 system. While BC could not directly reduce Fe(III) in Gt, it improved the cycling of Fe(III)/Fe(II) through complexing Fe(III) with its carboxyl group. Potential pathways were proposed for OFX degradation in the Gt/BC/H2O2 system.