Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia.
iES Landau, Institute for Environmental Sciences, RPTU Kaiserslautern-Landau, Landau, Germany.
Chemosphere. 2023 Jul;329:138628. doi: 10.1016/j.chemosphere.2023.138628. Epub 2023 Apr 7.
The present study investigated the adsorption mechanism of titanium dioxide nanoparticles (nTiO) on polyethylene microplastics (MPs) and the resulting photocatalytic properties. This effort was supported by ecotoxicological assessments of MPs with adsorbed nTiO on the immobility and behaviour of Daphnia magna in presence and absence of UV irradiation. The results showed that nTiO were rapidly adsorbed on the surface of MPs (72% of nTiO in 9 h). The experimental data fit well with the pseudo-second order kinetic model. Both suspended nTiO and nTiO immobilized on MPs exhibited comparable photocatalytic properties, with the latter showing a lower effect on Daphnia mobility. A likely explanation is that the suspended nTiO acted as a homogeneous catalyst under UV irradiation and generated hydroxyl radicals throughout the test vessel, whereas the nTiO adsorbed on MPs acted as a heterogeneous catalyst and generated hydroxyl radicals only locally and thus near the air-water interface. Consequently, Daphnia, which were hiding at the bottom of the test vessel, actively avoided exposure to hydroxyl radicals. These results suggest that the presence of MPs can modulate the phototoxicity of nTiO - at least the location at which it is active - under the studied conditions.
本研究调查了二氧化钛纳米粒子（nTiO）在聚乙烯微塑料（MPs）上的吸附机制及其光催化性能。这项工作得到了生态毒理学评估的支持，即在存在和不存在紫外辐射的情况下，评估了吸附有 nTiO 的 MPs 对大型溞的不活动和行为的影响。结果表明，nTiO 迅速被吸附在 MPs 表面上（9 小时内有 72%的 nTiO 被吸附）。实验数据与伪二级动力学模型拟合良好。悬浮的 nTiO 和固定在 MPs 上的 nTiO 都表现出相当的光催化性能，后者对大型溞的迁移性影响较小。一种可能的解释是，悬浮的 nTiO 在紫外辐射下充当均相催化剂，在整个测试容器中产生羟基自由基，而吸附在 MPs 上的 nTiO 则充当多相催化剂，仅在局部且因此在空气-水界面附近产生羟基自由基。因此，隐藏在测试容器底部的大型溞积极避免接触羟基自由基。这些结果表明，在研究条件下，MPs 的存在可以调节 nTiO 的光毒性——至少可以调节其活性位置。
