Abstract
This study investigated the degradation efficacy, kinetics, and mechanism of the ozone (O(3)) process and two enhanced O(3) processes (O(3)/peroxymonosulfate (O(3)/PMS) and O(3)/peroxymonosulfate/iron molybdates/biochar composite (O(3)/PMS/FeMoBC)), especially the O(3)/PMS/FeMoBC process, for the degradation of tetracycline (TC) in water. An FeMoBC sample was synthesized by the impregnation-pyrolysis method. The XRD results showed that the material loaded on BC was an iron molybdates composite, in which Fe(2)Mo(3)O(8) and FeMoO(4) accounted for 26.3% and 73.7% of the composite, respectively. The experiments showed that, for the O(3)/PMS/FeMoBC process, the optimum conditions were obtained at pH 6.8 ± 0.1, an initial concentration of TC of 0.03 mM, an FeMoBC dosage set at 200 mg/L, a gaseous O(3) concentration set at 3.6 mg/L, and a PMS concentration set at 30 μM. Under these reaction conditions, the degradation rate of TC in 8 min and 14 min reached 94.3% and 98.6%, respectively, and the TC could be reduced below the detection limit (10 μg/L) after 20 min of reaction. After recycling for five times, the degradation rate of TC could still reach about 40%. The introduction of FeMoBC into the O(3)/PMS system significantly improved the TC degradation efficacy and resistance to inorganic anion interference. Meanwhile, it enhanced the generation of hydroxyl radicals ((•)OH) and sulfate radicals (SO(4)(•-)), thus improving the oxidizing efficiency of TC in water. Material characterization analysis showed that FeMoBC has a well-developed porous structure and abundant active sites, which is beneficial for the degradation of pollutants. The reaction mechanism of the O(3)/PMS/FeMoBC system was speculated by the EPR technique and quenching experiments. The results showed that FeMoBC efficiently catalyzed the O(3)/PMS process to generate a variety of reactive oxygen species, leading to the efficient degradation of TC. There are four active oxidants in O(3)/PMS/FeMoBC system, namely (•)OH, SO(4)(•-), (1)O(2), and •O(2)(-). The order of their contribution importance was (•)OH, (1)O(2), SO(4)(•-), and •O(2)(-). This study provides an effective technological pathway for the removal of refractory organic matter in the aquatic environment.