Novel Synthesis Of Carbon Spheres Supported Nanoscale Zero-valent Iron For Removal Of Metronidazole

Metronidazole(MNZ)is one of the world's most important commercial antibiotics and widely used for treatment of infectious diseases in both humans and animals due to its high bacterial resistance.However,even trace concentration of antibiotics in water can pose a potential risk for aquatic and human.Nevertheless,large-scale application of the traditional techniques was often limited by the expensive investments in infrastructure,or complicated operation process.In recent years,nanoscale zero-valent iron(NZVI)technology has received growing attention in groundwater treatment and site remediation because of its large specific surface area,high reactivity,strong reducing ability,and environmentally friendliness.The NZVI particles were easy to aggregate and oxidize due to its magnetism and high reactivity.For further application,researchers try to support NZVI particles to overcome the aggregation and oxidation.In this research,carbon spheres(CSs)were prepared by hydrothermal method using glucose as raw materials.For the first time,carbon spheres-supported nanoscale zero-valent iron(NZVI/CSs)were synthesized as functionalized composite via liquid phase reduction method.The CSs,NZVI and NZVI/CSs were characterized by SEM,TEM,FTIR and XRD.The systematic characterization confirmed that NZVI was successfully loaded on the surface of CSs.Besides,the presence of CSs effectively decreased the aggregation of NZVI,resulting in higher reactivity,excellent stability and enhanced dispersion.By comparison,the removal efficiencies of MNZ with followed the order of NZVI/CSs>NZVI>CSs The results show that 94.18%of MNZ was removed using NZVI/CSs after 6 min,while only 36.45%and 8.78%of MNZ were removed using NZVI and CSs,respectively.In addition,Different important factors impacting on MNZ removal(including mass ratio of NZVI to CSs,initial concentration,pH value and solution temperature)were investigated as well.The results show that the ratio of 2:1 for NZVI/CSs can achieve the best removal efficiency within 90 min(90.89%).The removal efficiency was decreased by increasing initial pH value and MNZ concentration,and it was increased with the reaction temperature.Kinetics for the removal of MNZ using these NZVI/CSs composite fitted well to a revised two-parameter pseudo-first-order model.The possible degradation mechanism was proposed,which was based on the analysis of degraded products by high performance liquid chromatography-mass spectrometry(HPLC-MS).The galvanic cell system between NZVI and CSs was essential for enhancing MNZ reduction in aqueous solution.Overall,this study provides a promising alternative material for antibiotic waste water treatment.