Institute of Ecological and Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, China; College of Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, China.
Department of Chemical Engineering, Northwest Minzu University, Lanzhou, Gansu 730030, China.
Water Res. 2022 Oct 1;224:119024. doi: 10.1016/j.watres.2022.119024. Epub 2022 Aug 28.
The interaction between microplastics (MPs) and hydrophilic organic contaminants (HOCs) in natural water environment has recently raised great public attentions due to the potential toxicity to humans. However, the quantitative assessment is less studied. In this study, the interaction between ciprofloxacin (CIP) and ofloxacin (OFL) (two important HOCs) and virgin and aged polystyrene (PS) was investigated. The aged PS showed higher adsorption rate and capacity than the virgin PS, due to its larger surface area and more O-containing groups. The pH-dependent adsorption of CIP was higher than OFL on both virgin and aged PS; the maximum adsorption for both HOCs occurred at pH 5. The sequential orders of functional groups for the adsorption were discovered according to the study by the 2D correlation Fourier transform infrared spectroscopy. Several mechanisms existed for the interaction: (1) at 3.0 < pH < 5.0, the electrostatic attraction (EA) was inhibited while H-bond (HB) was dominant, accounting for > 60% of the total uptake; (2) at 5.0 < pH < 8.0, the contribution of EA increased to around 50-60% while HB decreased to 30-40%; (3) at 8.0 < pH < 10.0, EA, HB and π-π conjugation caused 30-40%, 25-40% and 20-45% of the total uptake, respectively; (4) at 10.0 < pH < 12.0, π-π conjugation accounted for 90-100%. Notably, higher adsorption of CIP was mainly attributed to the presence of secondary amino groups and its higher pK value, correspondingly leading to the additional ordinary HB and negative charge-assisted HB, and EA interactions with PS. This study further provides clear evidences on the risk of MPs and HOCs on humans and aqueous living organisms.
微塑料（MPs）与亲水性有机污染物（HOCs）在自然水环境中的相互作用，由于其对人类潜在的毒性，最近引起了公众的极大关注。然而，定量评估的研究较少。在这项研究中，研究了环丙沙星（CIP）和氧氟沙星（OFL）（两种重要的 HOCs）与原始和老化聚苯乙烯（PS）之间的相互作用。由于老化 PS 的比表面积更大，含有更多的含氧基团，因此其吸附速率和容量均高于原始 PS。CIP 的吸附随 pH 值变化的程度高于 OFL 在原始和老化 PS 上的吸附；两种 HOCs 的最大吸附均发生在 pH 5。根据二维相关傅里叶变换红外光谱的研究，发现了官能团的顺序。存在几种相互作用的机制：（1）在 3.0 < pH < 5.0 时，静电吸引（EA）受到抑制，而氢键（HB）占主导地位，占总吸附量的> 60%；（2）在 5.0 < pH < 8.0 时，EA 的贡献增加到 50-60%左右，而 HB 减少到 30-40%；（3）在 8.0 < pH < 10.0 时，EA、HB 和π-π共轭分别导致 30-40%、25-40%和 20-45%的总吸附；（4）在 10.0 < pH < 12.0 时，π-π共轭占 90-100%。值得注意的是，CIP 更高的吸附主要归因于仲氨基的存在及其更高的 pK 值，相应地导致了额外的普通氢键和带负电荷的氢键，以及与 PS 的 EA 相互作用。本研究进一步为 MPs 和 HOCs 对人类和水生生物的风险提供了明确的证据。
