Synergistic effect of ClO4- and Sr2+ adsorption on alginate-encapsulated organo-montmorillonite beads: Implication for radionuclide immobilization

Wuhui Luo; Qidong Huang; Philip Antwi; Binglin Guo; Keiko Sasaki

doi:10.1016/j.jcis.2019.10.049

Synergistic effect of ClO₄^- and Sr²⁺ adsorption on alginate-encapsulated organo-montmorillonite beads: Implication for radionuclide immobilization

J Colloid Interface Sci. 2020 Feb 15:560:338-348. doi: 10.1016/j.jcis.2019.10.049. Epub 2019 Oct 14.

Authors

Wuhui Luo¹, Qidong Huang², Philip Antwi², Binglin Guo³, Keiko Sasaki⁴

Affiliations

¹ School of Resources and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, PR China; Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan; Jiangxi Academy of Environmental Sciences, Nanchang 330077, PR China. Electronic address: luo070221@126.com.
² School of Resources and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, PR China.
³ Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan.
⁴ Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan. Electronic address: keikos@mine.kyushu-u.ac.jp.

PMID: 31635881
DOI: 10.1016/j.jcis.2019.10.049

Abstract

Perchlorate (ClO₄^-) and pertechnetate (TcO₄^-) exhibit similar adsorption characteristics on alkyl quaternary ammonium-modified montmorillonite (Mt), and ^99mTcO₄^- normally coexists with ⁹⁰Sr²⁺ in radionuclide-contaminated water. In this study, hexadecyl pyridinium (HDPy)-modified Mt (OMt) was encapsulated in alginate beads to inhibit HDPy release and simultaneously immobilize ClO₄^- and Sr²⁺ ions. The release of HDPy was remarkably reduced (78 times) from OMt after alginate encapsulation. Adsorption of ClO₄^- and Sr²⁺ on the obtained composite demonstrated synergistic effects, with adsorption capacities reaching 0.542 and 0.484 mmol/g, respectively. Compared to the single-adsorbate system, adsorption capacities of ClO₄^- and Sr²⁺ increased significantly. The characterization of solids using X-ray diffraction, Fourier transform infrared spectroscopy, ¹³C nuclear magnetic resonance, and X-ray photoelectron spectroscopy, as well as the chemical analysis of the aqueous solution, demonstrated that HDPy⁺-COO^- disintegration accounted for the adsorption synergy. HDPy was extracted from the Mt interlayer space during the synthesis of OMt/alginate and then partially re-intercalated back after interacting with ClO₄^- during the adsorption of ClO₄^- and/or Sr²⁺. In the binary-adsorbate system, the synergy-induced adsorption capacity was superior to many previously reported adsorbents, implying that OMt/alginate beads can be a promising adsorbent for the remediation of aqueous solutions contaminated with multiple radionuclides.

Keywords: Alginate; Organo-montmorillonite; Radionuclides immobilization; Simultaneous adsorption; Synergistic effect.