Study On The Process And Mechanism Of Amoxicillin Removal From Aqueous Solution By Three-dimensional Electrode Method

The potential genotoxicity and non-biodegradability of antibiotics in the natural water bodies threaten the survival of various living things and cause serious environmental pollution and destruction.Amoxicillin(AMX)is a widely used broad-spectrum β-lactam antibiotic,which is difficult to be degraded by secondary sewage treatment in traditional sewage treatment plants.Therefore,in this work,an experimental study was mainly conducted to effectively degrade AMX in an aqueous solution(AMX initial concentration 150 mg/L,TOC initial concentration 74.7 mg/L and COD initial concentration 406.4 mg/L)by using a three-dimensional(3D)electrode method.This work firstly compared the effects of a two-dimensional(2D)electrode reactor and a 3D electrode reactor filled with granular activated carbon(GAC)particle electrodes on the cyclic degradation of AMX wastewater.Compared with the 2D system,the efficiency of AMX wastewater treatment in the 3D-GAC system has been greatly improved,which proved the importance of particle electrode.Then,in order to improve the electrocatalytic activity of the particle electrode,Co3O4 catalyst was loaded on the GAC carrier by impregnation method,and the optimum manufacturing conditions of the particle electrode(Co3O4/GAC)were determined as the calcination temperature of 700℃5,the calcination time of 5 hours,and the impregnation time of 3 hours,respectively.The charge transfer at the electrode interface of Co3O4/GAC was faster than that of GAC.The lower Tafel slope of the 3D-Co3O4/GAC system(433.3 mV/dec)compared to the 3D-GAC system(648.2 mV/dec)showed its faster electrocatalytic reaction kinetics.Multipurpose optimization of operating conditions of the 3D-Co3O4/GAC system was carried out using the response surface methodology.Under the obtained optimum operating condition(current density 5.68 mA/cm2,electrolyte concentration 0.127 mol/L,particle electrode dosage 31.14 g,and treatment time 120 min),TOC removal efficiency of 85.24%could be achieved with a low electrical energy consumption of 0.073 kWh/g TOC,which were much improved compared to the 3D-GAC system(TOC removal efficiency of 41.93%and electrical energy consumption of 0.162 kWh/g TOC).In order to further improve the efficiency of AMX wastewater treatment,a 3DCo3O4/GAC-PMS system containing peroxymonosulfate(PMS)was constructed.This system was able to remove 100%AMX and 96.8%TOC by effectively generating sulfate radical by the catalytic action of Co2+ions.After five consecutive operations,the TOC concentration(8.03 mg/L)and COD concentration(54.86 mg/L)in the outlet wastewater of the 3D-Co3O4/GAC-PMS system still reached the"Emission standard for water pollutants in chemical synthesis pharmaceutical industry".The 3D-Co3O4/GAC-PMS system simultaneously degraded all three pharmaceuticals(amoxicillin,ciprofloxacin,and acetaminophen)with different chemical structures within 8 minutes of reaction time and removed 88.1%of TOC after 120 minutes of reaction,suggesting the system’s applicability for actual pharmaceutical industry wastewater treatment.Through the identification of intermediates by UPLC-MS,the degradation pathway of AMX in the 3D-Co3O4/GAC-PMS system could be analyzed.AMX was degraded mainly because reactive species attacked the C-C and C-N covalent bonds,resulting in the destruction of the four-membered β-lactam ring and the benzene ring.AMX molecules are gradually transformed into small molecules under the attack of reactive species,and later mineralized into H2O and CO2.