The Influence of Small Organic Molecules on Coagulation from the Perspective of Hydrolysis Competition and Crystallization

作者：Xuejia Zhang, Nigel Graham, Lei Xu, Wenzheng Yu, John Gregory · 发表于：Environmental Science & Technology · 年份：2021 · DOI：10.1021/acs.est.1c00869 · 被引用次数：55 · 研究领域：Coagulation and Flocculation Studies、Membrane Separation Technologies、Environmental remediation with nanomaterials

Most coagulation studies focus on pollutant removal or floc separation efficiency. However, to understand the mechanism of coagulation, it is necessary to explore the behavior of coagulation in terms of the interactions among the functional groups on the surface of the metal hydrolysis precipitates during the hydrolysis process. In this study, for the first time, aluminum sulfate (alum) was used to investigate such interactions over the whole process sequence of hydrolysis, coagulation, and crystallization with, and without (as a control), the presence of specific low molecular weight (LMW) (molecular weight < 1000 Da) organic compounds with different chemical bonds. It was observed that primary nanoparticles (NPs) of around 10 nm size were produced during the hydrolysis of alum. The presence of organic compounds was found to influence the coagulation performance by affecting the metal hydrolysis and the properties of the nanoparticles. At pH 7, ethylenediaminetetraacetic acid disodium salt (EDTA) delayed the time when the particles start to aggregate but increased the maximum size of the flocs, while citric acid caused the crystallization of amorphous hydrates and inhibited the coagulation performance. In contrast, glucose, benzoic acid (BEN), and tris(hydroxymethyl)aminomethane (THMAM) had no significant effect on the coagulation performance. Therefore, LMW organics can bond to the hydrolysis products of metal ions through key functional groups, such as carboxyl groups, and...