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| Influence of ions on the aggregation behavior of hematite nanoparticle in aqueous system |
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Abstract Influences of electrolytes (NaCl, CaCl2, KCl, K2SO4 and K2CrO4) on the hematite nanoparticle (Fe2O3NP) aggregation were investigated. The attachment efficiency (α) was applied to assess the alternations of aggregation behavior, and the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was utilized to elucidate the mechanisms underlying the observed changes. Results clearly showed that the aggregation behaviors were enhanced by electrolytes of higher valence and/or at higher concentration; anions exhibited greater effects on the aggregation of NPs than cations (e.g., K2SO4 had induced more significant aggregation than CaCl2 as comparing to KCl); K2CrO4 could enhance the aggregation more significantly than other electrolytes (0.5 mmol/L of K2CrO4 could induce great aggregation). Based on the DLVO theory, we suggested that increasing the concentration (within a relatively low range) and valence of electrolytes would promote the aggregation by decreasing the zeta potential (ζ) and the Debye length simultaneously; the greater impacts of anions and K2CrO4 on aggregation of NPs comparing to the cations were mainly induced by the dramaticall decrease of ζ; the ζ would remain relatively steady within relatively high concentration ranges of electrolytes, whereas the reduction of Debye length would become the key factor in promoting aggregation behaviors.
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Received: 21 December 2013
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