Efficient degradation of fluoroquinolone antibiotics in the landfill leachate by sludge biochar activated peracetic acid: Radical vs non-radical process

Peracetic acid (PAA) has been increasingly used as a disinfectant and oxidant in wastewater treatment. The activation of PAA was crucial for the oxidation of refractory contaminants in the wastewater. Herein, the sludge biochar (SDBC) was fabricated, and then used as the activator for PAA to degrade fluoroquinolone antibiotics (FQs). Results show that FQs underwent rapid degradation by SDBC/PAA system at neutral pH, and the first-order rate constant (kobs) of enrofloxacin (ENR, 0.0886 min−1) was higher than those of ciprofloxacin (CIP, 0.0313 min−1) and ofloxacin (OFL, 0.0327 min−1). FQs degradation conformed the first order kinetics. Scavenging experiments and EPR analysis indicated both radical and non-radical process contributed to FQs degradation, with non-radical process act as the dominant role. The abundant π electrons and carbon-containing functional groups on the surface of SDBC facilitated electron transfer, resulting in PAA activation for 1O2 generation; while the iron species on SDBC could also activate PAA to generate the organic radicals, i.e., CH3COO· and CH3COOO·. The degradation of FQs underwent the defluorination, decomposition and shedding of piperazine rings, and the toxicity of FQs was significantly diminished after treatment by SDBC/PAA. SDBC had excellent activity and reusability in PAA activation, and SDBC/PAA process could resist the interference by the complicated water matrices with wide pH adaptability. Hence, the non-radical dominated degradation of FQs by SDBC/PAA maintained high efficiency in the real landfill leachate. This work provides a promising strategy to eliminate antibiotics and its biological activity in the complicated water matrices.