Adsorption Behavior Of PA Microplastics For Typical Pollutants In Water Environment

With the rapid development of industry,the environmental pollution problem caused by it is becoming more and more serious.In the water environment,the most typical pollutants are microplastics.The complex structure and small diameter of microplastics make microplastics extremely easy to mix with other pollutants in the environment,thereby forming complex pollutants.Other pollutants,such as antibiotics,heavy metals and dyes,can also cause serious harm to the environment,because these pollutants are not easily decomposed,so they are difficult to digest after being absorbed by aquatic organisms,and can cause harm to the human body through the food chain.Sewage and wastewater containing these pollutants can not only affect the quality and appearance of water bodies,but also hinder the occurrence of photosynthesis of plants in water.At present,the methods used to remove pollutants in water mainly include adsorption,oxidation,electrolysis,etc.Among these methods,adsorption is the most commonly used and the most important method,so it has received widespread attention from the academic community.Although there are many studies on the adsorption of dyes,heavy metals and antibiotics,the aging mechanism of microplastics is still unclear in the academic community,and there is still a lack of research on the migration and transformation mechanism of pollutants.In view of this,this paper prepares aged PA microplastics by simulating indoor UV aging method,and characterizes the microplastics before and after aging by means of particle size determination,SEM,BET,XRD and other analytical methods.For typical pollutants in water,such as Roxar Arsine（ROX）,acid fuchsin,heavy metal Cr⁶⁺,etc.,are mainly studied by adsorption isotherm model to reveal the adsorption characteristics of PA microplastics before and after aging.The transfer behavior of plastics in the environment provides a basis,and also verifies the scientific nature of the adsorption mechanism of microplastics.The results of this study are as follows:（1）SEM analysis results show that the surface structure of microplastics will change after aging,and the microstructure will also be damaged to varying degrees;at the same time,the specific surface area of microplastics will decrease after aging,and the pore volume and pore size will also be reduced.become smaller;elemental analysis shows that the composition of C,H,and N of the aged PA microplastics changes to a certain extent,and the C content increases;particle size analysis shows that the structure of the PA microplastics is damaged after aging,and the average particle size of the microplastics changes.Small;FTIR analysis showed that the physical and chemical and micro-morphological structure changes mainly occurred after aging;XRD analysis results showed that the irradiation of ultraviolet light did not change the grains of microplastics.（2）The adsorption model shows that the adsorption and desorption process of PA on ROX can be well fitted by the pseudo-second-order model,and the comprehensive adsorption capacity can be roughly obtained.The more ROX adsorbed by microplastic PA,the more desorption.From the point of view of the time to reach the adsorption equilibrium,the adsorption rate of aged PA to ROX is much lower than that of original PA,indicating that the aging process reduces the adsorption capacity of PA to ROX.In addition,the effects of salinity and p H value on the adsorption process were also studied.The adsorption capacity of PA on ROX is gradually negatively correlated with the increase of salinity,and the adsorption capacity is the largest when the p H value is 4;the Langmuir model has better fitting effects on the adsorption isotherms of PA before and after aging,indicating that the adsorption process is mainly Mainly by monolayer adsorption.（3）The adsorption and desorption process of microplastic PA to acid fuchsin was well fitted by pseudo-second-order kinetic model.The results show that the adsorption and desorption processes of microplastic PA and acid fuchsin can be divided into three parts.From the perspective of the adsorption amount at equilibrium,the adsorption of acid fuchsin is relatively stable and difficult to desorb.The Freundlich model of isotherm adsorption has a high degree of fit for the original PA and its aged PA.The maximum adsorption capacity can be known from the calculated parameters.The maximum adsorption capacity of the aged PA for magenta is only 78%of that of the original PA,and the effect of the original PA is much higher.Adsorption effect on aged PA.（4）In the adsorption of heavy metal Cr⁶⁺by microplastic PA,the adsorption and desorption process of original PA microplastic conforms to the pseudo-second-order kinetics.The original PA can reach the adsorption equilibrium within 480 minutes,and the desorption reaches the desorption equilibrium within 240 minutes.The aging PA meets the pseudo-second-order kinetics.The first-order kinetic model shows that the adsorption process of aged PA is a physical adsorption process;while in the isotherm adsorption,the original PA conforms to the Freundlich model,and the aged PA conforms to the Langmuir model.The research results show that the adsorption mechanism of microplastics for different pollutants is different,so it is necessary to further explore the adsorption mechanism of microplastics in order to establish a more suitable adsorption model.