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Bentonite nanoparticle stability and the effect of fulvic acids: Experiments and modelling

Seher, Holger; Geckeis, Horst; Fanghänel, Thomas; Schäfer, Thorsten

Abstract:
In this study, the critical coagulation concentration (CCC) for FEBEX bentonite colloids is determined by colloid coagulation studies under variation of pH, electrolyte concentration, and fulvic acid (GoHy-573FA) content. For CaCl$_{2}$ electrolyte solution, a pH-independent Ca-CCC of 1 mmol L$^{-1}$ is found. In the case of NaCl background electrolyte, a pH-dependent Na-CCC can be determined with 15 ± 5 mmol L$^{-1}$ at pH 6, 20 ± 5 mmol L$^{-1}$ at pH 7, 200 ± 50 mmol L$^{-1}$ at pH 8, 250 ± 50 mmol L$^{-1}$ at pH 9, and 350 ± 100 mmol L$^{-1}$ at pH 10, respectively. The addition of 1 mg L$^{-1}$ dissolved organic carbon in the form of fulvic acid (FA) increases the Ca-CCC to 2 mmol L$^{-1}$. An association of FA with FEBEX bentonite colloids as surface coating can clearly be identified by scanning transmission X-ray microscopy (STXM). The experimental bentonite stability results are described by means of an extended DLVO (Derjaguin–Landau–Verwey–Overbeek) approach summing up hydration forces, short-range Born repulsion, van der Waals attraction, and electrical double layer repulsion. The measured zeta (ζ)-potential of the bentonite colloids is applied as platelet face electrokinetic potential and the edge electrokinetic potential is estimated by the combination of silica and alumina ζ-potential data in the ratio given by the FEBEX bentonite structural formula. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000131896
Veröffentlicht am 30.04.2021
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Nukleare Entsorgung (INE)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 2504-5377
KITopen-ID: 1000131896
Erschienen in Colloids and Interfaces
Verlag MDPI
Band 4
Heft 2
Seiten Art.-Nr.: 16
Schlagwörter colloid stability; CCC; FEBEX bentonite; DLVO; zeta potential
Nachgewiesen in Scopus
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