Construction Of Reactive Electrochemical Filter System And Study On The Degradation Of Norfloxacin

Electrochemical oxidation process,has emerged as a promising technology for the destruction of various toxic refractory organic pollutants in aqueous,due to its mild reaction conditions,strong oxidation ability,easy operation and environmental compatibility.However,the mass transfer rate of parallel plate electrodes system is very low,which lead to long residence time,high equipment investment cost,low current efficiency and high energy consumption of the conventional electrochemical oxidation system.It is therefore necessary and significant to take effective measures to improve the mass transfer rate of electrochemical oxidation system for the application of the water treatment technology.In this paper,tubular Ti/SnO₂-Sb/PbO₂ membrane electrodes were used as the cores to build reactive electrochemical filter systems,which improved the mass transfer rate of pollutants from the aqueous phase to the electrode surface by maximally compressing the thickness of the boundary layer.And the system achieved the rapid and efficient degradation of norfloxacin from water.Major conclusions drawn from this study are summarized as follows:?1?The prepared tubular Ti/SnO₂-Sb/PbO₂ membrane electrodes exhibited excellent physical performance,electrochemical performance and electrooxidation performance:?1?the pore structure of electrode was well-developed,and the average pore diameter and penetration flux were 30.2?m and 51.72 m³ m^-2 h^-1 bar^-1,respectively;?2?these electrodes exhibited electrochemical performance.The accelerated life was up to 888 h,which was equivalent to the actual life of 253.42 years at the current density of 10 m A cm^-2,and the electrode had huge electrochemical active area,the electrochemical porosity and R_f were 88.4%and 4408.3,respectively;and?3?the electrochemical oxidation performance was superior,under the same experimental conditions,the reaction rate of norfloxacin was up to 0.295 min^-1,which was 2.27times of the tubular Ti/SnO₂-Sb membrane electrode.?2?The reactive electrochemical filter systems,which were constructed by the tubular Ti/SnO₂-Sb/PbO₂ membrane electrodes,exhibited high mass transfer performance and strong oxidation performance in flow-through mode.A convection-enhanced rate constant of 1.92×10^-4 m s^-1 was achieved,which was improved by 1² orders of magnitude compared with the traditional parallel plate electrodes system(10^-610^-5 m s^-1).And the reaction rate and oxidation flux of norfloxacin were 0.295 min^-1 and 0.173 mol m^-2 h^-1,which were 15.53 times and 15.73times of flow-by mode,respectively,under the same experimental conditions.?3?The rapid and efficient degradation of norfloxcain was realized in the system.Experiments results showed the degradation process of norfloxacin was consistent with the pseudo-first-order kinetic.Under the optimal experimental conditions,norfloxacin(2.5 L,50mg L^-1)was almost completely degraded in 10 min,and the reaction rate was as high as 0.407min^-1.The degradation intermediates of norfloxacin were analyzed by using high-resolution mass spectrometer,the results showed that the main intermediates were C₁₆H₁₆O₅N₃F,C₁₅H₁₆O₄N₃F,C₁₄H₁₆O₃N₃F,C₁₃H₁₁O₄N₂F,C₁₂H₁₁O₃N₂F,C₁₆H₁₉O₄N₃,C₁₆H₁₉O₆N₃,C₁₅H₁₉O₅N₃ and C₁₄H₁₉O₄N₃ in the degradation process and two competitive processes occurred simultaneously during the·OH attract:destruction of piperazine ring and quinolone construction.And the degradation of norfloxacin was stable,without environmental risk and low energy.