Journal
JOURNAL OF ENVIRONMENTAL SCIENCES
Volume 38, Issue -, Pages 103-109Publisher
SCIENCE PRESS
DOI: 10.1016/j.jes.2015.04.014
Keywords
Nanoparticles; Coagulation; Effective coagulation concentration; Al3+
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Funding
- Chinese Academy of Sciences
- Open Foundation of State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences [SKLECRA2015OFP10]
- Natural Science Foundation of Heilong Jiang Province
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In recent years, engineered nanoparticles, as a new group of contaminants emerging in natural water, have been given more attention. In order to understand the behavior of nanoparticles in the conventional water treatment process, three kinds of nanoparticle suspensions, namely multi-walled carbon nanotube-humic acid (MWCNT-HA), multiwalled carbon nanotube-N, N-dimethylformamide (MWCNT-DMF) and nanoTiO(2)-humic acid (TiO2-HA) were employed to investigate their coagulation removal efficiencies with varying aluminum chloride (AlCl3) concentrations. Results showed that nanoparticle removal rate curves had a reverse U shape with increasing concentration of aluminum ion (Al3+). More than 90% of nanoparticles could be effectively removed by an appropriate Al3+ concentration. At higher Al3+ concentration, nanoparticles would be restabilized. The hydrodynamic particle size of nanoparticles was found to be the crucial factor influencing the effective concentration range (ECR) of Al3+ for nanoparticle removal. The ECR of Al3+ followed the order MWCNT-DMF > MWCNT-HA > TiO2-HA, which is the reverse of the nanoparticle size trend. At a given concentration, smaller nanoparticles carry more surface charges, and thus consume more coagulants for neutralization. Therefore, over-saturation occurred at relatively higher Al3+ concentration and a wider ECR was obtained. The ECR became broader with increasing pH because of the smaller hydrodynamic particle size of nanoparticles at higher pH values. A high ionic strength of NaCl can also widen the ECR due to its strong potential to compress the electric double layer. It was concluded that it is important to adjust the dose of Al3+ in the ECR for nanoparticle removal in water treatment. (C) 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.
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