Study On The Effect Of Microplastics On The Degradation Of Tetracycline In CoFe₂O₄/PMS System

Microplastics are produced in high quantities and used extensively worldwide,and their impact on the environment and human health as a new pollutant has received great attention in recent years.The increasing emission of microplastics,and its high environmental durability can form compound pollutants with other organic pollutants.which has multiple and complex impacts on the ecological environment and human health.Studies have pointed out that microplastics can have an impact on the degradation of pollutants under natural conditions or light,and microplastics and antibiotics in the aqueous environment have inevitably coexisted,and their effects on the degradation of antibiotics are positive or negative,and there are few research reports in this regard.Therefore,in this study,we investigated the effect of advanced oxidation systems on the degradation of tetracycline hydrochloride in the presence of microplastics and investigated the pathways of influence.In this study,two typical microplastics,polypropylene and polyethylene were used as research objects to prepare the transitional bimetallic material cobalt ferrite（CoFe₂O₄）activated permonosulfate system to degrade TCH,and the effects of PP and PE on the degradation of TCH by adding PP and PE respectively were investigated.The adsorption properties of PE microplastics on TCH and quantum chemical calculations based on density functional theory deduce the potential influence pathways of PP and PE on TCH degradation.The results of the study showed that:（1）The CoFe₂O₄/PMS system has a high degradation effect on TCH,with degradation of 94.95%at 60 min,and the degradation process conformed to the quasi-secondary kinetic model.The active oxidant that plays the main role is singlet oxygen（¹O₂）,followed by superoxide radicals(O₂^·-)and sulfate radicals(SO₄^·-).The transition metal ions on the catalyst surface participate in the cyclic redox reaction to achieve efficient catalytic effect.（2）With the increase of PP and PE dosage,the degradation rate of TCH at 100mg/L increased by 4.3%and 1.42%,respectively.The particle size of PP and PE microplastics did not affect the degradation of TCH at the same dosage.The degradation promotion effect of the original PP and PE microplastics on TCH was greater than that of the aged treated microplastics.（3）PP and PE improved the dispersion of catalytic materials,which could promote the degradation of TCH.PP and PE microplastics had certain adsorption properties on TCH,with adsorption capacities of 0.083 mg/g and 0.053 mg/g,respectively.After 15and 30 days of ageing treatment,the adsorption amounts of PP on TCH increased by37.35%and 74.7%,respectively.The adsorption amounts of PE on TCH increased by48.54%and 53.91%,respectively.However,there was a depletion of free radicals in the system by PP and PE.The post-aging treatment made PP and PE more susceptible to free radical attack and showed an inhibitory effect on the degradation of TCH.Chemical theory calculations indicate that when PP and PE are bonded to TCH through physical interaction,it changes the electron cloud distribution,electrophilic reaction sites and susceptibility to free radical attack sites of the frontier molecules of TCH,which has a potential impact on the degradation pathway of TCH.In this study explores the effects of PP and PE on the degradation of TCH in CoFe₂O₄/PMS systems,and provides a further theoretical reference for the impact of microplastic pollution on the environment.