Facilely prepared heterogeneous Fenton catalyst Fe(Fe0.69Al0.31)2O4@C for catalytic wet peroxide oxidation of ciprofloxacin in batch and continuous reactor: Reaction intermediates and toxicity evaluation

Herein, by using a simple co-precipitation method Al-doped magnetite spinel nanoparticle encapsulated in the carbon matrix Fe(Fe0.69Al0.31)2O4@C was synthesised and its catalytic activity was examined as a heterogeneous Fenton catalyst towards the catalytic wet peroxide oxidation (CWPO) of antibiotic pollutant 20 ppm ciprofloxacin (CIP) in batch and continuous reactors. Under the optimized conditions, 0.5 g center dot L-1 Fe(Fe0.69Al0.31)2O4@C in batch reactor mineralized 51 % of CIP was achieved within 180 min at 50 degrees C and pH 3 by utilizing 1.2 mM or 4S H2O2 (S = stoichiometry; 47 mol H2O2:1 mol CIP) which is significantly less concentration compared to other heterogeneous Fenton catalysts. Impressive long-lasting catalytic activity was demonstrated in the up-flow fixed bed reactor, for 110 h with 44 % TOC removal and less than 1 ppm Fe leaching in the effluent water. Kinetic studies on the rate of decomposition of H2O2 revealed that Fe(Fe0.69Al0.31)2O4@C effectively decomposed the H2O2 like the homogeneous Fenton catalyst. The XPS results confirmed the influence of Al on iron ions in the magnetite structure through a substantial shift in higher binding energy for Fe3+ and introduced a more electropositive character on the Fe3+(delta+) that successively expedites the kinetically slow Fe3+ reduction reaction with H2O2 to produce HOO center dot. The pi electrons of the graphitic carbon facilitate the electron transfer between the carbon matrix and Fe(Fe0.69Al0.31)2O4 nanoparticles to enhance the CIP degradation. The acute toxicity assessment studies validated the non-toxic nature of the effluent water obtained from batch and continuous reactors. A degradation pathway was proposed based on the eleven intermediate products identified using LC-HRMS analysis.