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Energies 2017, 10(2), 223;

Alkaline Earth Element Adsorption onto PAA-Coated Magnetic Nanoparticles

Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX 77005, USA
Department of Civil, Environmental, and Ocean Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA
Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, Austin, TX 78712, USA
Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada
Author to whom correspondence should be addressed.
Academic Editor: Dongsheng Wen
Received: 3 January 2017 / Revised: 2 February 2017 / Accepted: 8 February 2017 / Published: 14 February 2017
(This article belongs to the Special Issue Nanotechnology for Oil and Gas Applications)
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In this paper, we present a study on the adsorption of calcium (Ca2+) onto polyacrylic acid-functionalized iron-oxide magnetic nanoparticles (PAA-MNPs) to gain an insight into the adsorption behavior of alkaline earth elements at conditions typical of produced water from hydraulic fracturing. An aqueous co-precipitation method was employed to fabricate iron oxide magnetic nanoparticles, whose surface was first coated with amine and then by PAA. To evaluate the Ca2+ adsorption capacity by PAA-MNPs, the Ca2+ adsorption isotherm was measured in batch as a function of pH and sodium chlorite (electrolyte) concentration. A surface complexation model accounting for the coulombic forces in the diffuse double layer was developed to describe the competitive adsorption of protons (H+) and Ca2+ onto the anionic carboxyl ligands of the PAA-MNPs. Measurements show that Ca2+ adsorption is significant above pH 5 and decreases with the electrolyte concentration. Upon adsorption, the nanoparticle suspension destabilizes and creates large clusters, which favor an efficient magnetic separation of the PAA-MNPs, therefore, helping their recovery and recycle. The model agrees well with the experiments and predicts that the maximum adsorption capacity can be achieved within the pH range of the produced water, although that maximum declines with the electrolyte concentration. View Full-Text
Keywords: adsorption; calcium; functionalized superparamagnetic iron oxide nanoparticles; polyacrylic acid; surface complexation modelling adsorption; calcium; functionalized superparamagnetic iron oxide nanoparticles; polyacrylic acid; surface complexation modelling

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Wang, Q.; Prigiobbe, V.; Huh, C.; Bryant, S.L. Alkaline Earth Element Adsorption onto PAA-Coated Magnetic Nanoparticles. Energies 2017, 10, 223.

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