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Effect of crystallization of settled aluminum hydroxide precipitate on "dissolved Al"
Yu, Wenzheng; Xu, Lei; Lei, Kaiyu; Gregory, John
2018-10-15
Source PublicationWATER RESEARCH
ISSN0043-1354
Volume143Pages:346-354
AbstractWhen aluminum salts are added to water at around neutral pH, a precipitate of Al hydroxide is formed very rapidly. Initially the precipitate is in the form of nano-scale primary particles, which then aggregate to form flocs. The nature of the flocs depends greatly on the solution composition, for instance on the presence of humic acid (HA), which not only increases the size of the primary nanoparticles, but also decreases the connection points between them. The nanoparticles become smaller with aging, both with and without HA, as a result of crystallization. The aggregated amorphous nanoparticles (settled flocs) undergo a room temperature structural modification best characterized as a disorder-to-order transition, following elimination of water. During this process, the apparent Al concentration in the supernatant of water increases with age. The "dissolved Al" concentration in the supernatant becomes higher with increasing pH and, to some extent, in the presence of HA. However, it can be shown that the "dissolved Al" in the supernatant exists in the form of crystalline nano-particles or larger clusters, which are detached from the settled flocs. TEM results confirmed that HA only adsorbed on the surface of nano particles during the coagulation process, which shows precipitate nanoparticles formed firstly during sweep coagulation before the adsorption of HA or complexed Al3+-HA. However, the adsorbed outer layer of HA does not change the crystallization process for the inner part of nano-particles. This laboratory study may have implications for the release of Al from sediments into lake water, following addition of coagulants to lower phosphorus concentrations. (C) 2018 Elsevier Ltd. All rights reserved.
Department中国科学院饮用水科学与技术重点实验室
KeywordResidual Al Crystallization Flocs Ageing Nanoparticle
Document Type期刊论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/41345
Collection中国科学院饮用水科学与技术重点实验室
Recommended Citation
GB/T 7714
Yu, Wenzheng,Xu, Lei,Lei, Kaiyu,et al. Effect of crystallization of settled aluminum hydroxide precipitate on "dissolved Al"[J]. WATER RESEARCH,2018,143:346-354.
APA Yu, Wenzheng,Xu, Lei,Lei, Kaiyu,&Gregory, John.(2018).Effect of crystallization of settled aluminum hydroxide precipitate on "dissolved Al".WATER RESEARCH,143,346-354.
MLA Yu, Wenzheng,et al."Effect of crystallization of settled aluminum hydroxide precipitate on "dissolved Al"".WATER RESEARCH 143(2018):346-354.
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