Competitive Adsorption Of Typical Heavy Metals And Endocrine Disruptors By Biodegradable Microplastics

Microplastics(MPs)have strong hydrophobicity and large specific surface area,which can strongly adsorb pollutants in the environment,thus affecting the migration and transformation of pollutants in the environment and their bioavailability.Due to the nondegradable or refractory properties of plastics,they bring potential risks to the ecological environment.Degradable plastics can be completely decomposed into water and carbon dioxide under the action of microorganisms,with complete degradation,is one of the important materials to replace the general plastic.Meanwhile,the pollution of heavy metals and endocrine disruptors is also a common problem in water environment,so it is of great significance to study the adsorption mechanism of degradable microplastics on typical heavy metals and endocrine disruptors.This study selected gather adipic acid/butyl glycol terephthalate(PBAT)and poly(butyl diacid butyl glycol ester(PBS),As the representative of the micro degradable plastics research typical heavy metals arsenic(As),cadmium(Cd)and endocrine disruptor bisphenol A(BPA),17 alpha ethinyl estradiol(platform)in the biodegradable plastic,which is competitive,adsorption properties,In order to provide basic data for revealing the influence of biodegradable microplastics on the migration and transformation of pollutants in water environment,we further analyzed the biodegradable microplastics by the energy distribution theory of sites,XPS and FTIR characterization methods.The main conclusions are as follows:(1)The adsorption kinetics of typical heavy metals As and Cd by biodegradable microplastics is most suitable for fitting with quasi-second-order kinetic model;The linear model,Freundlich model and Langmuir model can fit the isothermal adsorption data well.The adsorption effect of PBS on heavy metals was better than that of PBAT,and the adsorption effect of degradable microplastics on As was better than that of Cd.Thermodynamic studies show that the adsorption of As and Cd by biodegradable microplastics is a spontaneous endothermic and entropy-adding process,that is,high temperature is conducive to the adsorption of heavy metals by biodegradable microplastics.(2)Further analyze the competitive adsorption characteristics of PBS between As and Cd based on the site energy distribution theory.The average site energy of PBS in double solute system was lower than that in single solute system.The heterogeneity of As decreases while that of Cd increases.The effect of As on Cd is greater than that of Cd on As in the double solute system.There is a certain competitive effect between the two,and As has a competitive advantage in the dual solute system.(3)The adsorption kinetics of typical endocrine disruptors BPA and EE2 by degradable microplastics could be well fitted by Elovich model and quasi-second-order model.The linear model,Freundlich model and Langmuir model can fit the isothermal adsorption data well.The adsorption effect of PBS on endocrine disruptors was better than that of PBAT,and the adsorption effect of degradable microplastics on EE2 was better than that of BPA.Thermodynamic studies showed that the adsorption of BPA and EE2 by biodegradable microplastics was a process of spontaneous exothermic and entropy reduction,that is,low temperature was conducive to the adsorption of endocrine disruptors by biodegradable microplastics.(4)Based on the site energy distribution theory,the competitive adsorption of PBS between BPA and EE2 was further analyzed.The average site energy and heterogeneity of PBS increased in the two-solute system.The heterogeneity fluctuation of EE2 was greater than that of BPA,and the adsorption capacity of EE2 decreased while that of BPA increased,indicating that the influence of BPA on EE2 was greater than that of EE2 on BPA in the adsorption process of the two substances.BPA has a competitive advantage in the dual solute system.