Adsorption Mechanism Of The Atrazine By Microplastics Of Polystyrene,Polyethylene And Polypropylene In Aqueous Environment

As a sort of emerging pollutant,microplastics has gradually aged in the environment with changes in their physicochemical properties and may act as carriers of other pollutants in water to form complex pollutants.Therefore,it is important to study the aging characteristics of typical microplastics in water environment and their adsorption mechanisms on organic pollutants.In this paper,three of the most ubiquitous microplastics,including polyethylene（PE）,polypropylene（PP）and polystyrene（PS）,were selected to investigate the aging performance characteristics of microplastics and their kinetic and thermodynamic mechanisms of atrazine（ATZ）adsorption in water,adopting simulated UV irradiation,alkali treatment and high temperature-freeze-thaw treatment,respectively.The results showed that the surface roughness of PS,PE and PP all increased after the processes of UV irradiation,alkali treatment and high temperature-freeze-thaw,with different degrees of cracking and surface corrosion.The adsorption capacities of ATZ by microplastics after different aging processes were higher than that of the original microplastics,especially with the significant increase in adsorption capacity after UV irradiation.The adsorption capacities of PS,PE and PP were 1.24,1.65 and 1.52 folds than that of the original microplastics,respectively.The adsorption experiments and data fitting results showed that the adsorption is in accordance with the quasi-secondary kinetic model and the adsorption isotherm is in accordance with the Langmuir model,showing a non-linear adsorption characteristic,which is a multilayer adsorption process combining physical and chemical adsorption.The adsorption capacities of PS,PE and PP for ATZ were maximum when the aqueous p H were around neutral condition;the adsorption efficiency of microplastics for ATZ increased with temperature up and ionic intensity of the water quality in the background;while the adsorption of PS,PE and PP for ATZ exhibited the weaken tendency with increasing humic acid（HA）concentration;coexisting anions such as chloride（Cl^-）,sulphate ion(SO₄^2-)and bicarbonate ion（HCO₃^-）increased the adsorption capacity of ATZ by microplastics to varying degrees,while coexisting cations such as magnesium ion of Mg²⁺and calcium Ca²⁺inhibited adsorption.The adsorption processes of PS,PE and PP on ATZ are affected by hydrogen bonding,electrostatic gravitational forces,hydrophobic interactions,as well as related to the different properties of the pollutants such as polarity,hydrophobicity and ionization.