Carrier Effect Of Amide Herbicides On The Surface Of Microplastics

Metolachlor and butachlor are widely used as amide herbicides to remove weeds in farmland,but due to their non-degradability and residual characteristics after use,they cause serious environmental pollution problems.The migration of metolachlor and butachlor through osmosis and transpiration will change the original balance mechanism in the ecological environment and cause toxic symptoms.At the same time,the problem of microplastics pollution has become a new problem and challenge of global pollution.More and more evidences show that microplastics can adsorb organic pollutants as carriers,which may affect the distribution and bioavailability of organic pollutants in the environment.To clarify the process and mechanism of the adsorption and desorption of organic pollutants by microplastics is of great significance for clarifying the corresponding changes in the environmental behavior of organic pollutants.Therefore,this study uses microplastics as the research material,and on the basis of exploring the mechanism of its interaction with metolachlor and butachlor,explores the adsorption performance of microplastics for amide herbicides and their ability to interact with each other.And further explore whether the two have a greater impact on the environment.（1）In this study,the physical and chemical properties of microplastics were analyzed,including scanning electron microscopy analysis（SEM）,Mapping element analysis（Mapping）,X-ray diffraction analysis（XRD）,Fourier infrared spectroscopy（FTIR）and isocharge point analysis（p Hpzc）.The results show that the aging process of the microplastics will cause the microplastics to contain more oxygen-containing functional groups.After aging,the specific surface area of the microplastics increases,the water film area is developed,and the adsorption sites are reduced,which is more unfavorable for adsorption.（2）Factors affecting the selection of adsorption experiments include:adsorption time,initial concentration,solution p H,solution salt ion concentration and aging microplastics.The results show that the optimal initial concentration of metolachlor for microplastics adsorption is 25μg/L;the time to reach adsorption equilibrium is 2 h;the optimal adsorption is under neutral conditions,the salt ion concentration of the solution has little influence,and the aging microplastics make microplastics adsorption capacity decreases.The optimal initial concentration of butachlor for microplastics adsorption is 12μg/L;the time to reach adsorption equilibrium is 1 h;the most suitable adsorption under neutral conditions,the salt ion concentration of the solution has little influence,and the aging microplastics reduce the adsorption capacity of the microplastics.（3）Using pseudo-first-order kinetics（PFO）and pseudo-second-order（PSO）kinetic models for fitting,it is found that microplastics are more in line with pseudo-second-order kinetics,Langmuir,Freundlich,Linear,Dubinin-Raduskevich（D-R）,Temkin,and Redlich-Peterson（R-P）isotherm models have been performed,Calculated microplastics:polyethylene（referred to as PE）,polypropylene（referred to as PP）,polyvinyl chloride（referred to as PVC）,the maximum adsorption capacity of metolachlor was 11.33μg/g,12.23μg/g and 14.97μg/g,respectively;the maximum adsorption capacity of butachlor for microplastics（PE,PP,PVC）are 13.65μg/g,14.82μg/g and 18.88μg/g,respectively.（4）Using 0.2 mol/L CaCl₂ solution to conduct desorption experiments on three kinds of microplastics,the salt desorption phenomenon is obvious.Due to the presence of Ca²⁺in the CaCl₂ environment,the ion diffusion rate of the solution is increased,and the particle agglomeration is promoted.The two herbicides are stripped from the microplastics relatively quickly（PE and PP have a smaller adsorption gap for metolachlor）,especially the most significant impact on PVC.（5）The adsorption effect of microplastics and amide herbicides is relatively low,and the two will not form large-scale composite harmful pollution,and there will be no migration of harmful substances in large groups.