State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
The Key Laboratory of Water and Sediment Sciences, Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, PR China.
J Hazard Mater. 2023 Apr 15;448:130978. doi: 10.1016/j.jhazmat.2023.130978. Epub 2023 Feb 9.
The occurrence of microplastics (MPs) and even nanoplastics (NPs) in tap water has raised considerable attention. As a pre-treatment and also the most important process in drinking water treatment plants, coagulation has been widely studied to remove MPs, but few studies focused on the removal pattern and mechanism of NPs, especially no study paid attention to the coagulation enhanced by prehydrolysed Al-Fe bimetallic coagulants. Therefore, in this study, polymeric species and coagulation behaviour of MPs and NPs influenced by Fe fraction in polymeric Al-Fe coagulants were investigated. Special attention was given to the residual Al and the floc formation mechanism. The results showed that asynchronous hydrolysis of Al and Fe sharply decreases the polymeric species in coagulants and that the increase of Fe proportion changes the sulfate sedimentation morphology from dendritic to layered structures. Fe weakened the electrostatic neutralization effect and inhibited the removal of NPs but enhanced that of MPs. Compared with monomeric coagulants, the residual Al decreased by 17.4 % and 53.2 % in the MP and NP systems (p < 0.01), respectively. With no new bonds detected in flocs, the interaction between micro/nanoplastics and Al/Fe was merely electrostatic adsorption. According to the mechanism analysis, sweep flocculation and electrostatic neutralization were the dominant removal pathways of MPs and NPs, respectively. This work provides a better coagulant option for removing micro/nanoplastics and minimizing Al residue, which has promising potential for application in water purification.
自来水中微塑料（MPs）甚至纳米塑料（NPs）的出现引起了相当大的关注。作为饮用水处理厂的预处理和最重要的过程，混凝已被广泛研究用于去除 MPs，但很少有研究关注 NPs 的去除模式和机制，特别是没有研究关注由预水解 Al-Fe 双金属混凝剂增强的混凝。因此，在本研究中，研究了 MPs 和 NPs 中受聚合 Al-Fe 混凝剂中 Fe 部分影响的聚合物种和混凝行为。特别关注残留 Al 和絮体形成机制。结果表明，Al 和 Fe 的异步水解急剧降低了混凝剂中的聚合物种，Fe 比例的增加改变了硫酸盐沉淀形态，从树枝状变为层状结构。Fe 削弱了静电中和效应，抑制了 NPs 的去除，但增强了 MPs 的去除。与单体混凝剂相比，MP 和 NP 体系中的残留 Al 分别降低了 17.4%和 53.2%（p<0.01）。在絮体中未检测到新键，微/纳米塑料与 Al/Fe 之间的相互作用仅是静电吸附。根据机理分析，扫流絮凝和静电中和分别是 MPs 和 NPs 的主要去除途径。这项工作为去除微/纳米塑料和最小化 Al 残留提供了更好的混凝剂选择，对于水净化具有广阔的应用前景。
