State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Yangtze River Delta Branch, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Yiwu City, Zhejiang Province 322000, China.
School of Environmental and Chemical Engineering, Foshan University, Foshan 528000, China.
Sci Total Environ. 2022 Jun 25;827:154228. doi: 10.1016/j.scitotenv.2022.154228. Epub 2022 Mar 1.
An abundance of nano-particles have been exposed to water environment. Owing to the particle size effects, nano-particles are inclined to absorb harmful substances and increase their levels of toxicity. In this study, the existence state, aggregation and settlement characteristics of nano-particles in the natural water are studied. Influenced by the structural layer repulsion, nano-particles have higher stability in natural water. When coagulants were added, nano-particles could effectively aggregate with slow flocculation speed and relatively small flocs size without hydraulic shearing due to the significant effect of Brownian motion. It is worth noting that the aggregated flocs formed by Brownian motion showed high strength and strong ability to resist hydraulic disturbance, and thus the flocs were harder to break. This is because the combination among nano-particles under hydraulic shearing is the result of a single-point chain-to-chain aggregation mode, while that under the Brownian motion is the result of multi-points face-to-face aggregation mode. Therefore, in the process of re-flocculation, flocs formed by the Brownian motion were more compact. This study provides a new view in nano-particles treatment for both the in-situ treatment process of natural water body and the regular water treatment plants.
大量纳米颗粒已经暴露在水环境中。由于颗粒尺寸的影响，纳米颗粒容易吸收有害物质，增加其毒性水平。在这项研究中，研究了自然水中纳米颗粒的存在状态、聚集和沉降特性。受结构层排斥的影响，纳米颗粒在天然水中具有更高的稳定性。当添加混凝剂时，由于布朗运动的显著影响，纳米颗粒可以有效地聚集，具有较慢的絮凝速度和相对较小的絮体尺寸，而不会受到水力剪切的影响。值得注意的是，布朗运动形成的聚集絮体具有高强度和抵抗水力干扰的强能力，因此絮体更难破裂。这是因为在水力剪切下纳米颗粒的结合是单点链到链聚集模式的结果，而在布朗运动下是多点面对面聚集模式的结果。因此，在再絮凝过程中，布朗运动形成的絮体更加紧密。这项研究为自然水体的原位处理过程和常规水处理厂提供了纳米颗粒处理的新视角。
