Study On The Performance Of Catalytic Microbubble Ozonation By Layered Double Oxide For The Treatment Of Amoxicillin Wastewater

In this study,Layered Double Hydroxide（LDH）was prepared as a precursor by a co-precipitation method and calcined to obtain Layered Double Oxide（LDO）,which was termed the“CCF catalyst”.The optimal preparation conditions for the CCF catalyst were studied,and the physical structure characteristics and surface chemical properties of the optimal catalyst were analyzed using various characterization methods.It was applied to catalyze the microbubble ozonation（MB/O₃/CCF）reaction system of amoxicillin（AMX）simulated wastewater.The efficiency and influencing factors of MB/O₃/CCF for AMX were investigated,and a reaction mechanism and possible AMX degradation pathways was proposed.The results are as follows:The optimal preparation conditions for CCF catalysts were obtained by optimizing the addition ratio of metal ion,p H value during precipitation,water bath heating time,and calcination time during the catalyst preparation process.The catalytic performance was evaluated in a coarse bubble ozonation（CB/O₃/CCF）reaction system,and the optimal preparation conditions for the CCF catalysts were as follows:the molar ratio of Co²⁺,Cu²⁺,and Fe³⁺was 2.4:0.6:1,p H of 11.5,water bath time of 6h,and calcination time of 4h.The characterization results of XRD,FTIR,XPS,BET-BJH,SEM,and the p H value of the point of zero charge(p H_PZC)indicated that the CCF catalyst had a rough surface,uniform size,layered structure,and was a mesoporous material with a large specific surface area.The main phases are Co₃O₄,Cu O,and Fe₃O₄.The content ratio of Co²⁺,Cu²⁺,and Fe³⁺is2.69:0.65:1,and each element was evenly dispersed on the catalyst surface.The oxygen on CCF surface mainly belongs to lattice oxygen with a content of 73.01%and the p H_PZCvalue is 6.51,which is close to neutral.Among coarse bubble ozonation（CB/O₃）,CB/O₃/CCF,microbubble ozonation（MB/O₃）,and MB/O₃/CCF reaction systems,the MB/O₃/CCF system exhibited the best treatment effects.The degradation ratio of AMX exceeded 99%within 25 min,and the mineralization ratio reached 60.40%within 120 min.The reactions conformed to the pseudo-first-order kinetic model,and the synergetic effect between microbubbles,ozone,and catalyst was 6.8.The ozone and catalyst dosages were positively correlated with the degradation rate and mineralization rates of AMX.Under acidic conditions of p H 3,the degradation rate of AMX could be promoted,the reaction rate constant could achieve0.3056 min^-1,but the mineralization rate was inhibited by 20.47%.The highest mineralization rate was 66.26%at p H 9.The initial concentration of AMX is negatively correlated with the degradation rate,and the mineralization rate reaches its maximum value of 60.40%at an initial concentration of 50 mg·L^-1.The common inorganic anions in water such as NO₃^-,Cl^-,and SO₄^2-,had relatively weak effect on the removal of AMX in the MB/O₃/CCF system,with an inhibition of no more than 5%on the degradation rate of AMX and no more than 7%on the mineralization rate.The MB/O₃/CCF system still achieved a mineralization rate of 46.67%after four repeated uses of the CCF catalyst.Treatment with norfloxacin（NOR）and tetracycline hydrochloride（TCH）achieved mineralization rates of 45.09%and 54.14%respectively,indicating that CCF catalyst has potential for engineering application.The CCF catalyst significantly promoted ozone decomposition,with a decomposition rate constant that increased from 0.0241 min^-1 for ozone self-decomposition to 0.1065min^-1 for catalytic ozone decomposition,an increased of 3.42 times.The reactive oxygen species affecting AMX degradation in the MB/O₃/CCF system were verified.The experiments revealed that AMX degradation was mainly due to the oxidation of ozone and singlet oxygen.The oxidation of AMX by MB/O₃/CCF was related to the enhancement of ozone mass transfer by microbubbles,adsorption and catalytic decomposition of ozone by CCF catalysts,and electrostatic interactions between ozone microbubbles,organic pollutants,and catalyst surface charges.The intermediate products of AMX were determined based on the UPLC-MS results.The degradation pathways of AMX likely mainly involve oxidative ring-opening reaction,isomerization and hydrolysis.