Microplastics (MPs) are novel pollutants that can adsorb heavy metals in water environments and migrate together as carriers and are prone to aging due to the light in water. However, few reports have been published on the synergistic behavior and effects of these different types of aged MPs on the adsorption and desorption of Cr(VI). Here, two MP types─polyamide (PA) and polylactic acid (PLA)─were aged by UV irradiation, and the adsorption and desorption behaviors of MPs on Cr(VI) were studied. The results indicated that UV light can rapidly age MPs. After the MPs were exposed to UV light, their specific surface area, negative charge, and oxygenic groups increased, resulting in enhanced hydrophilicity. The aged MPs depicted a markedly enhanced adsorption capacity for Cr(VI) compared with the results of aged-PA > pristine-PA > aged-PLA > pristine-PLA. The process followed the Langmuir and pseudo-second-order models, confirming that chemical and monolayer adsorption are the primary processes involved in the adsorption of Cr(VI) by aged MPs. Cr(VI) was more easily desorbed in the simulated gastric fluid environment. The desorption rate of aged MPs was lower than that of pristine MPs because of their stronger binding forces to Cr(VI). The binding of Cr(VI) to MPs mainly depends on synergistic mechanisms such as electrostatic attraction, reduction reactions, and chelation of oxygenic groups. This study clarifies the reciprocity mechanism between aging MPs and Cr(VI) and provides further insights and guidance for controlling the joint pollution between MPs and heavy metal pollutants in the future.

中文翻译：

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Cr（VI） 在水溶液中对两种典型紫外老化微塑料的吸附和解吸行为


微塑料 （MP） 是一种新型污染物，可以吸附水环境中的重金属并作为载体一起迁移，并且由于水中光线的作用而容易老化。然而，关于这些不同类型的老年 MP 的协同行为和对 Cr（VI） 吸附和解吸影响的报道很少。在这里，两种 MP 类型——聚酰胺 （PA） 和聚乳酸 （PLA）——通过紫外线照射老化，并研究了 MPS 对 Cr（VI） 的吸附和解吸行为。结果表明，紫外线会迅速使 MP 老化。MP 暴露在紫外光下后，其比表面积、负电荷和氧基增加，导致亲水性增强。与老化的 PA > 原始 PA > 老化的 PLA > 原始 PLA 的结果相比，老年议员对 Cr（VI） 的吸附能力显著增强。该过程遵循 Langmuir 和准二级模型，证实化学吸附和单层吸附是老化 MP 吸附 Cr（VI） 的主要过程。老年 MP 的解吸率低于原始 MP，因为它们对 Cr（VI） 的结合力更强。Cr（VI） 与 MP 的结合主要取决于协同机制，例如静电吸引、还原反应和氧基的螯合。本研究阐明了老龄化 MP 与 Cr（VI） 之间的互惠机制，为未来控制 MPS 与重金属污染物的联合污染提供了进一步的见解和指导。