Electrochemical mineralization of antibiotic ceftazidime with SnO2-Al2O3/CNT anode: Enhanced performance by peroxydisulfate/Fenton activation and degradation pathway

Abstract

Sol-gel synthesis of a novel SnO2-Al2O3/CNT anode was conducted and adopted to the electrocatalyzing decomposition of aqueous ceftazidime in this study. The physical structure and chemical composition were observed and characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The results present SnO2 and Al2O3 nanoparticles were uniformly and compactly distributed on the carbon nanotubes, which is recognized to contributing to the recycling stability and catalytic activity improvements. The electrodeposited behaviors were investigated by cyclic voltammograms, linear sweep voltammograms and hydroxyl radical generation test, illustrating this anode exhibited excellent catalyzing properties with increased production of •OH radicals. The removal efficiency of ceftazidime was monitored with high-performance liquid chromatograph (HPLC) and results indicated an enhancement from 40 % to nearly 90 % with SnO2-Al2O3/CNT anode. In addition, the activation by peroxydisulfate (PDS) and Fenton reaction improved the mineralization degree of ceftazidime, with 45.2 % TOC removal by adding 2 mM PDS and 55.1 % TOC removal by adding 2 mM Fe2+, compared with 40 % TOC removal by anodic oxidation alone. Although the mineralization rate of electrooxidation-PDS process was lower, it exhibited a broader pH stability range than electrooxidation-Fenton coupling process. The mechanism analysis indicate electrooxidation-PDS was dominated by SO4− radicals, which is favored at basic solutions. The degradation intermediates were detected by liquid chromatograph-mass spectrometer technology, and a complete degradation pathway was proposed. This method proves a simple, clean and efficient degradation method for removal of trace refractory pollutants in aqueous environment without the necessity of chemical recovery and pH adjustment.