Study On Degradation Of Cephalosporin Antibiotics In Water By Lanthanum Copper Modified Carbon Nanotube Electrode

PPCPs is a kind of global,low concentration of persistent refractory pollutants.Electrochemical method has a good advantage in the degradation of PPCPs.The electrocatalytic oxidation method was adopted to remove low concentration of cephalosporin antibiotics.In order to fabricate a novel electrode with higher catalytic activity,faster in degradation and lower current density.The carbon nanotubes was used as the electrode substrate.And the carbon nanotubes was dopede with Lanthanum and copper through the impregnation.The electrode was characterized and used to remove ceftazidime.The main contents are as follows:(1)The carbon nanotubes were purified by boiled nitric acid and reflux for 8h.Then the purified carbon nanotubes were charactized by SEM and FTIR.The electrode was characterized by SEM,XRD,XPS,cyclic voltammetry and tafel curves.The results showed that the surface of the carbon nanotubes purified many new functional groups,each characterization analysis showed that compared to the modified electrode on the electrode performance before modification and electrode life have improved significantly.(2)The electrode dopede with lanthanum and copper was used to degrade ceftazidime.The optimised degradation conditions are as follows:the current density of 0.8 mA·cm-2,a distance of 2 cm,pH of 6,supporting electrolyte concentration is 1.0 g·L-1,solution volume is 100 mL.The removal efficiency could reach upon 90%under the optimized degradation conditions contrast to the removal efficiency of unmodified electrode was less than 40%.It proved the dopede electrode improved a lot on the catalytic properties.The removal efficincy of 8 kinds of cephalosporin antibiotics at the same conditions could also reach 90%after 60 min degradation.(3)The change of current efficiency was studied in the process of electrocatalytic degradation of ceftazidime.The current efficiency of modified electrode was higher than the unmodified electrode under different conditions.The maximum current efficiency of modified was about 20%?30%.The current efficiency was gradually decline with the increasing of degradation time.(4)The reaction kinetics under different influence factors of modified and unmodified electrode were studied.The reaction kinetics of modified and unmodified electrode are consistent with one or two order kinetics curve under current density,electrode spacing,electrolyte concentration,pH and solution volume.(5)Sampling after different reaction time and the samples were dected by LC-MS to analyse the intermediate products.The lactam four-member ring in the ceftazidime tension.It leads to degrade easily in this structure.The structure of the two membered ring structure of hydrogen peroxide coupled with the six membered ring is also not stable.There are also several unsaturated double bonds of chiral centers on ceftazidime and it is easy broken.The C-N bond branched are weak and it easily break into small molecules under the attack of strong oxidizing substances and electronic.The structure and the keys are easy to damage and fracture.