单宁酸在疏水性微塑料/水界面上的吸附

Adsorption of tannic acid onto hydrophobic microplastics from water

为理解水环境中新污染物微塑料对溶解性天然有机质的吸附作用,以单宁酸为天然有机质的模型化合物,考察了聚丙烯(PP)、聚甲醛(POM)、聚苯乙烯(PS)、聚氯乙烯(PVC)和聚对苯二甲酸乙二醇酯(PET)5种疏水性微塑料对水相中单宁酸吸附的动力学和等温线.实验结果表明,吸附在8 d内达到表观平衡,吸附过程可以很好地用假二级吸附动力学模型描述,吸附等温线更符合朗格缪尔吸附等温模型(质量浓度范围为10~150 mg/L),单宁酸在微塑料/水界面的吸附为单分子层吸附.具有非极性表面的PP、PS和PVC对单宁酸吸附的朗格缪尔吸附亲和力常数(0.070~0.115 L/mg)大于具有弱极性表面的POM和PET(0.042~0.045 L/mg),这主要是由于不同微塑料表面疏水性的差异,而非不同微塑料与单宁酸之间相互作用的差异.

In order to understand the adsorption of dissolved organic matter on the emerging contaminants microplastics in the environment,the adsorption kinetics and isotherms of tannic acid(a model dissolved organic matter)from aqueous phase on five hydrophobic microplastics,including polypropylene(PP),polyoxymethylene(POM),polystyrene(PS),poly(vinyl chloride)(PVC),and poly(ethylene terephthalate)(PET),were investigated.The experimental results show that the apparent adsorption equilibrium is achieved within 8 d.The adsorption process can be well described by the pseudo-second-order adsorption kinetic model.The adsorption isotherms are all well fitted by Langmuir model with equilibrium concentrations in the range of 10 to 150 mg/L.The adsorption of tannic acid at the microplastics-water interface is in the form of a monomolecular layer.The Langmuir adsorption affinity coefficients of PP,PS,and PVC with non-polar surfaces(0.070 to 0.115 L/mg)are greater than those of POM and PET with weakly polar surfaces(0.042 to 0.045 mg/L),which is dominated by the differences in the hydrophobicity of microplastic surfaces,rather than the differences in the interactions between tannic acid and microplastics.