原始及老化微塑料对磺胺嘧啶的吸附性能与机理

Adsorption Performance and Mechanism of Raw and Aging Microplastics on Sulfadiazine

微塑料(microplastics,MPs)在水环境中可以作为有机物的载体,对有机污染物的迁移转化和毒性效应产生影响。文中选取聚氯乙烯(PVC)、聚丙烯(PP)和聚苯乙烯(PS)3种极性和亲疏水性不同的MPs颗粒为研究对象,采用酸碱浸泡法对MPs进行老化,探讨原始和老化的MPs对磺胺嘧啶(SDZ)吸附性能的影响。试验结果表明,酸碱老化(1 mol/L H;SO;或NaOH)使MPs表面出现粗糙褶皱或孔隙结构。3种MPs的吸附量顺序为PVC(0.616 mg/g)>PS(0.480 mg/g)>PP(0.438mg/g),吸附动力学符合二级动力学方程,说明3种MPs对SDZ吸附是多个吸附阶段共同作用的结果;老化MPs吸附等温线符合Freundlich模型,说明老化MPs的吸附位点和活性基团的分布不均匀,导致吸附SDZ过程以多层吸附为主。PVC的吸附热力学表明,原始与老化PVC对SDZ的吸附效率均随着温度升高而降低,吸附为自发、放热的吸附反应。3种MPs对SDZ的主要吸附机制为疏水作用和孔隙填充,还可能存在卤键作用、氢键作用和π-π共轭作用等。

Microplastics(MPs) can be used as carriers of organic matter in water environment,which may affect the migration and transformation of organic pollutants and their toxic effects.In this paper,three types of MPs including polyvinyl chloride( PVC),polypropylene(PP) and polystyrene(PS),with different characteristics of polarity and hydrophilicity/hydrophobicity,were selected as the objects.MPs could be aging caused by acid or base leaching method,and the influences of raw and aging MPs on the adsorption performance of sulfadiazine(SDZ) were discussed.The aging MPs showed rough surface and had obvious folds and pore structures due to the leaching(H;SO;or NaOH with concentration of 1 mol/L) process.The orders of adsorption equilibrium for the three MPs were as follows:PVC(0.616 mg/g) >PS(0.480 mg/g) >PP(0.438 mg/g),and the adsorption kinetics was in accordance with the second-order kinetic equation,indicating that multiple adsorption stages were responsible for the adsorption process of SDZ on MPs.The adsorption isotherm of aging MPs conformed to Freundlich model,suggesting that the distribution of adsorption sites and active groups was not uniform,which caused the occurrence of multilayer adsorption.Regarding PVC,the thermodynamics analysis showed that the adsorption capacity of SDZ on raw and aging PVC decreased with the increase of temperature.The adsorption reaction was spontaneous and exothermic.The main mechanisms adsorption of SDZ on MPs are considered to be the hydrophobic interaction and pore filling,with co-function of halogen bond,hydrogen bond and π-π conjugation.