Modified Titanium Based PbO₂ Anode For Electrocatalytic Degradation Of Antibiotics Wastewater

Tetracyclines（TC_S）,lincosamides（LC_S）and fluoroquinolones（QN_S）antibiotics are the three typical antibiotics in water pollutants.Their complex structures and poor biochemical properties have caused great pressure on the environment.At present,the common methods for treating antibiotic wastewater are mainly biochemical,physical and chemical methods.Among them,electrocatalytic oxidation technology in chemical methods has become the important means to treat biodegradable and organic toxic pollutants.The advantages of electrocatalytic oxidation technology include high oxidation efficiency,low cost and mild conditions,making it one of the most attractive methods for antibiotic wastewater treatment.Preparation of anode materials with excellent catalytic performance and economic efficiency is the key to electrocatalytic degradation technology.Doxycycline,lincomycin and enrofloxacin,typical representatives of TC_S,LC_S and QN_Scategories of antibiotics,are selected as target degradants.Titanium flakes are employed as the substrate material,and boron nitride/samarium（BN/Sm）,titanium oxide/neodymium（Ti₄O₇/Nd）and tungsten trioxide/scandium（WO₃/Sc）are introduced in the preparation of Ti/PbO₂ electrodeposition to obtain Ti/PbO₂-BN-Sm,Ti/PbO₂-Ti₄O₇-Nd and Ti/PbO₂-WO₃-Sc electrodes,respectively for electrocatalytic degradation of lincomycin,doxycycline and enrofloxacin.The main studies are as follows.（1）Lincomycin is a typical lincomidine antibiotic,and its solution stirring at different p H conditions generates a large number of bubbles adsorbed on the electrode,thus weakening the degradation effect.The introduction of BN/Sm has an excellent effect on the performance of Ti/PbO₂ electrode,and the modified Ti/PbO₂ electrode has dense and compact surface and smaller cone structure,which has longer lifetime and higher electrocatalytic activity.The experiments show that the removal rate of lincomycin and COD achieve 92.50%and 89.32%,respectively,when the Ti/PbO₂-BN-Sm electrode is degraded at optimized conditions(Na₂SO₄ 6.0 g L^-1,30°C,current density of 20 m A cm^-2,p H 9)for 3 h.The degradation process of lincomycin is consistent with quasi primary kinetics.The samples are analyzed by LC-MS and a complete degradation mechanism of lincomycin is proposed based on the identified structures of typical intermediates such as ethanedioic acid.（2）Doxycycline is a typical tetracycline antibiotic and contains lots of hydroxyl and cyclic structure.Ti₄O₇ has a wide window of stabilization potential in aqueous solution,with corrosion resistance close to that of ceramic materials,and long life in both strongly acidic and alkaline environments.Meanwhile,the Nd-doped anode has excellent degradation performance against polycyclic antibiotics.It is demonstrated that the fabricated Ti/PbO₂-Ti₄O₇-Nd electrode has excellent corrosion resistance,and the introduction of Ti₄O₇ and Nd improves the oxygen evolution potential and electrocatalytic activity of Ti/PbO₂ and reduces the charge transfer impedance.The degradation rate and COD removal rate of doxycycline achieve 98.85%and 94.69%,respectively,after 3 h of degradation under the optimized conditions.The accelerated lifetime and cycling experiments reveal that the Ti/PbO₂-Ti₄O₇-Nd electrode has excellent recyclability.Samples are taken after 3 h of degradation in the final optimized conditions for LC-MS analysis.The samples are analyzed by LC-MS and a complete degradation mechanism of doxycycline is proposed based on the identified structures of typical intermediates such as succinic acid.（3）Enrofloxacin is a typical fluoroquinolone antibiotic,with structure of cyclopropyl,piperazine and other difficult to degrade groups.It shows that WO₃ exhibits excellent catalytic performance in the treatment of organic pollutants,while Sc is often used as a catalyst in organic reactions and contributes greatly to ring-opening reactions as well as petroleum cracking processes.It has been proved that the introduction of WO₃/Sc changes the surface morphology of the Ti/PbO₂ electrode,resulting in higher oxygen evolution potential,lower impedance,better stability and excellent electrocatalytic activity.The degradation rate and COD removal rate of enrofloxacin achieve 94.06%and 90.31%,respectively,after 3 h of degradation under the optimized conditions.Tests on the target electrode show that the Ti/PbO_2-WO₃-Sc electrode has favorable recyclability.The samples are analyzed by LC-MS and a complete mechanism of enrofloxacin degradation is proposed based on the identified structures of typical intermediates such as fumaric acid and methionine.The above results show that the Ti/PbO₂-BN-Sm,Ti/PbO₂-Ti₄O₇-Nd and Ti/PbO₂-WO₃-Sc electrodes prepared by modifying the active layer of lead dioxide are effective in degrading antibiotic wastewater with lincosamides,tetracyclines and fluoroquinolones.The prepared electrodes have excellent cycle life performance and low degradation energy consumption under optimized conditions,which provide a reference for green and efficient treatment of actual antibiotic wastewater.