| Microplastic refers to the heterogeneous plastic particle mixture with different color and shape,whose particle size is from several nanometers,micrometers to several millimeters.At present,the research direction of microplastics can be roughly divided into three aspects:(1)investigation and analysis of microplastics pollution in different regions and water bodies;(2)the threat and toxicological effect of microplastics on biology and ecology;(3)the adsorption,desorption and transportation of microplastics on environmental pollutants.Due to its physical and chemical properties,microplastics can adsorb organic pollutants in the environment.Pollutants are transported to the organism or the unpolluted ecological environment with microplastics as the carrier,and then released,threatening human security.At present,there are few researches on the adsorption characteristics and mechanism of micro plastics to methyl orange,and the adsorption of micro plastics to organic pollutants is still in its infancy.In this study,the microplastic PA-66,PA-6,PP,POM and PTFE were used as adsorbents to study their adsorption characteristics with characteristic organic pollutants methyl orange.PA-66 was characterized by scanning electron microscope,specific surface area test,micro Raman spectrum analysis,FTIR attenuated total reflection spectrum,combined with adsorption kinetics and adsorption isotherm model,the mechanism of adsorption of methyl orange by nylon-6 and nylon-6 was studied.The change characteristics and causes of adsorption capacity of microplastics under the influence of particle size,salinity,p H and aging conditions were discussed,which provided theoretical basis for the migration behavior of organic pollutants carried by microplastics in the environment and data support for the toxicological analysis of microplastics in the marine environment.The main conclusions are as follows:(1)There are obvious differences in the adsorption of methyl orange by different materials of microplastics.Among them,the adsorption capacity of nylon-66 to methyl orange is the largest,up to 9.57 mg/g;the adsorption kinetic process includes the initial fast reaction stage and the subsequent slow reaction stage,and finally reaches equilibrium.The adsorption process is in accordance with the quasi second-order kinetic equation of lagergren.The results of isothermal adsorption experiments show that nylon-66 mainly adsorbs in single molecular layer at low temperature,and heterogeneous multi-layer chemical adsorption occurs at high temperature.(2)In a certain range,the particle size of microplastics has a significant negative correlation with the adsorption capacity of methyl orange,which is related to the effective adsorption sites provided by microplastics.However,when the particle size of microplastics exceeds a certain degree,the particle size continues to decrease,and the adsorption capacity will not change.The increase of salinity and p H inhibited the adsorption,and the adsorption capacity of microplastics decreased significantly after aging treatment in laboratory.(3)The ability of microplastics to adsorb methyl orange is related to crystallinity and molecular polarity.The lower the crystallinity,the stronger the molecular polarity and the greater the adsorption capacity.In addition,the main reason for the adsorption of methyl orange by nylon-66 is the electrostatic effect and the formation of hydrogen bond;there is no chemical change in the adsorption process of nylon-6,mainly physical adsorption. |
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