Study On The Efficiency And Mechanism Of Degradation Of Atenolol Based On Ultrasound Coupling BiFeO₃ Nano Materials

As a typical beta-blocker,atenolol（ATL）is widely used to treat cardiovascular diseases.Due to the special physicochemical properties,ATL is not easy to be removed by the traditional treatment process of wastewater treatment plants.Therefore,ATL is discharged into the environment constantly,giving a menace to human health and ecological environment.Recently,the technology of degradation of organic contaminant under ultrasound coupling piezoelectric materials as a green and efficient advanced oxidation processes（AOPs）has attracted people’s attention.The single-crystalline BiFeO₃nanorods and nanosheets were fabricated by hydrothermal method.It was found that the removal efficiency of ATL by ultrasound coupling BiFeO₃ nanorods and nanosheets was up to 91.08%and 70.20%,respectively,and the synergy coefficient of BiFeO₃ nanorods and nanosheets was 2.67 and 1.37,respectively,which was mainly caused by the difference of piezoelectric potential generated by different morphology of BiFeO₃.It was found that with the increase of ultrasonic frequency and power,the degradation efficiency of ATL was enhanced under ultrasound coupling BiFeO₃.At different ultrasonic frequencies,the synergistic relationship was 100 kHz>40 kHz>20kHz>200 kHz>400 kHz.In order to determine the optimal ultrasonic frequency,COMSOL Multiphysics software was utilized to simulate ultrasonic sound fields.It was found that the effective distance of ultrasound decreased with the increase of frequency,therefore,the optimal frequency was 100 kHz based on practical application and removal efficiency of ATL.The simulation of ultrasonic sound fields of different powers showed that the maximum positive/negative pressure of ultrasound and the induced piezoelectric potential of BiFeO₃ increased with the increase of power.Additionally,the degradation efficiency of ATL with BiFeO₃dosage had an optimal value of 1.5 g/L,and the removal efficiency was up to 90.30%.It was found that 4 active substances,·OH,·O₂^-,h⁺and ¹O₂contributed to the system in varying degrees in aerobic condition,and their contribution relationship was·OH>¹O₂>h⁺>·O₂^-,while·OH and h⁺contributed more in this system in anaerobic condition.Due to ultrasonic cavitation and the reaction of H₂O/OH^-with h⁺produced by mechanical induced BiFeO₃,the contribution of·OH to the system occupied an important position.There were 4 active sites of ATL molecular structure which were vulnerable to attack by active substances during the degradation process,and it was speculated that there are 4possible degradation pathways,which were hydroxylation of benzene ring,cleavage isopropyl amino group,cleavage of ether bond and cleavage of formamide part in acetamide branch chain,respectively.The acute toxicity and chronic toxicity of byproducts to fish,green algae and daphnia was reduced in varying degrees compared with ATL.By exploring the effects of typical water quality parameters on this system,it was found that the degradation efficiency of ATL increased with the decrease of the initial concentration of ATL,and the relationship between the degradation rate and the initial concentration of the target degradation was consistent with the Langmuir-Hinshelwood pseudo-first-order kinetic model.Different pH conditions has significant effects on the system,and the optimal pH condition was at 11.Three anions(Br^-,CO₃^2-/HCO₃^-and HPO₄^2-/H₂PO₄^-),two cations(NH₄⁺and Fe²⁺),two concentrations of HA and different natural water bodies had an impact on removal efficiency and degradation rate of ATL.Only Fe²⁺promoted the degradation of ATL,while others inhibited in varying degrees.