Effect of Organic Matter on the Flocculation of Colloidal Montmorillonite: A Modeling Approach

Furukawa, Yôko

doi:10.2112/jcoastres-d-11-00128.1

Cited by 21 publications

(10 citation statements)

References 44 publications

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“…The similarity of the results obtained after one direct ultra-centrifugation step (S3.5 UC , 9.0 ± 0.2%) is noticeable. A slightly higher recovery of clay colloids is obtained in the presence of fulvic acids (S3.5 UC,FA , 12.1 ± 0.1%), which indicates that the negatively charged FA may have stabilized a part of the montmorillonite colloids initially present in dispersion (Kretzschmar et al, 1998;Furukawa and Watkins, 2012).…”

Section: Ion and Colloid Concentrationsmentioning

confidence: 93%

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Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions

Norrfors

Bouby

Heck

et al. 2015

Applied Clay Science

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Bentonite is planned to be used as a technical barrier in the final storage of spent nuclear fuel and high level vitrified waste. In contact with ground water of low ionic strength, montmorillonite colloids may be released from the bentonite buffer and thereby enhance the transport of radionuclides (RNs) sorbed. In the present case, clay colloids represent aggregates of several clay mineral layers. It is of major importance to determine RN sorption properties for different sizes of montmorillonite aggregates, since size fractionation may occur during particle transport in natural media. In this study, a protocol for size fractionation of clay aggregates is developed, by sequential and direct centrifugation, in the presence and absence of organic matter. Seven colloidal fractions of different mean aggregate sizes are obtained ranging, when considering the mean equivalent hydrodynamic sphere diameter (ESD), from~960 nm down to~85 nm. Applying mathematical treatments (Jennings and Parslow, 1988) and approximating the clay aggregates to regular disc-shaped stacks of clay mineral sheets result in mean surface diameters varying from~1.5 μm down to~190 nm. All these colloidal fractions are characterized by XRD, IC and ICP-OES where they are found to have the same chemical composition. The number of edge sites (aluminol and silanol) is estimated (in mol/kg) for each colloidal fraction according to (Tournassat et al., 2003). It is calculated from the mean particle sizes obtained from AsFlFFF and PCS measurements, where the clay aggregates are approximated to regular disc-shaped stacks of clay mineral sheets. The estimated number of edge sites varies significantly for the different clay dispersions. In addition, stability studies using the various clay colloidal fractions are performed by the addition of NaCl, CaCl 2 or MgCl 2 , in the presence or absence of organic matter, where no difference in stability is found.

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Section: Ion and Colloid Concentrationsmentioning

confidence: 93%

“…In addition, experiments in the presence or absence of FA are performed, since FA is known to stabilize montmorillonite particles (Furukawa and Watkins, 2012). The clay particle concentration is fixed to 10 mg/L by prior dilution throughout all measurements, and all the supernatants listed in Table 1 are studied.…”

Section: Dispersionmentioning

confidence: 99%

Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions

Norrfors

Bouby

Heck

et al. 2015

Applied Clay Science

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“…The bulk behavior of suspended soft particles, such as flocculation, cannot always be predicted from the electrokinetic data alone [23]. The EPM of a soft particle depends on the attenuation of electrical potential in the vicinity of the surface, which in turn depends not only on the properties of host aqueous solution but also on the water and ion permeability of the soft layer.…”

Section: Introductionmentioning

confidence: 99%

The surface properties of Shewanella putrefaciens 200 and S. oneidensis MR-1: the effect of pH and terminal electron acceptors

Furukawa

Dale

2013

Geochem Trans

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BackgroundWe investigated the surface characteristics of two strains of Shewanella sp., S. oneidensis MR-1 and S. putrefaciens 200, that were grown under aerobic conditions as well as under anaerobic conditions with trimethylamine oxide (TMAO) as the electron acceptor. The investigation focused on the experimental determination of electrophoretic mobility (EPM) under a range of pH and ionic strength, as well as by subsequent modeling in which Shewanella cells were considered to be soft particles with water- and ion-permeable outermost layers.ResultsThe soft layer of p200 is significantly more highly charged (i.e., more negative) than that of MR-1. The effect of electron acceptor on the soft particle characteristics of Shewanella sp. is complex. The fixed charge density, which is a measure of the deionized and deprotonated functional groups in the soft layer polymers, is slightly greater (i.e., more negative) for aerobically grown p200 than for p200 grown with TMAO. On the other hand, the fixed charge density of aerobically grown MR1 is slightly less than that of p200 grown with TMAO. The effect of pH on the soft particle characteristics is also complex, and does not exhibit a clear pH-dependent trend.ConclusionsThe Shewanella surface characteristics were attributed to the nature of the outermost soft layer, the extracellular polymeric substances (EPS) in case of p200 and lypopolysaccharides (LPS) in case of MR1 which generally lacks EPS. The growth conditions (i.e., aerobic vs. anaerobic TMAO) have an influence on the soft layer characteristics of Shewanella sp. cells. Meanwhile, the clear pH dependency of the mechanical and morphological characteristics of EPS and LPS layers, observed in previous studies through atomic force microscopy, adhesion tests and spectroscopies, cannot be corroborated by the electrohydrodynamics-based soft particle characteristics which does not exhibited a clear pH dependency in this study. While the electrohydrodynamics-based soft-particle model is a useful tool in understanding bacteria’s surface properties, it needs to be supplemented with other characterization methods and models (e.g., chemical and micromechanical) in order to comprehensively address all of the surface-related characteristics important in environmental and other aqueous processes.

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“…For example, Shen and Maa (2016b) have produced bimodal FSDs of kaolinite suspensions with different dosages of guar gum in one of their mixing chamber tests. Multipeak FSDs are also reported in other studies focusing on the effects of organic substances on montmorillonite flocculation with cationic (such as chitosan), neutral (such as guar gum), or anionic (such as xanthan) EPS (Furukawa & Watkins, 2012;Zhang et al, 2013;Tan et al, 2012Tan et al, , 2014Furukawa et al, 2014). The occurrence of multimodality may be because of heterogeneous particle composition, irregular shaped flocs, limitation of floc size measuring technologies (that refer to spherical particles), and so on.…”

Section: Journal Of Geophysical Research: Oceansmentioning

confidence: 56%

An Approach to Modeling Biofilm Growth During the Flocculation of Suspended Cohesive Sediments

et al. 2019

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The floc size distribution (FSD) is crucial to predict cohesive sediment dynamics in aquatic environments. Recently, increasing attention has been given to biofilm effects on the FSDs of suspended particles since the presence of biofilms on particle surfaces may lead to larger flocs and thus higher settling velocities. In this study, results from a settling column experiment conducted by Tang and Maggi (2018; https://doi.org/10.1002/2017JG004165) under nutrient‐free and biomass‐free, nutrient‐affected and biomass‐free, and nutrient‐affected and biomass‐affected conditions, with different suspended sediment concentrations, shear rates, and nutrient concentrations, have been used to validate modeled FSDs that is based on the population balance equation solved by the quadrature method of moments. In addition to the processes of aggregation and breakage, the effects of biofilm are expressed in the growth term of the population balance equation. The logistic growth pattern is used to account for an increase in biomass, which is primarily controlled by the specific growth rate and the carrying capacity. In this study, the biofilm growth rate is assumed nutrient dependent, and the carrying capacity of floc size is hypothesized to be proportional to the Kolmogorov microscale. With eight size classes to interpret a simulated FSD, the predicted and observed FSDs exhibit a reasonable match for all nutrient‐free and biomass‐free, nutrient‐affected and biomass‐free, and nutrient‐affected and biomass‐affected conditions. This simplified bioflocculation model fills the gap between the simulations of the FSDs of cohesive sediments without and with biofilms and has the potential to be included in large‐scale models in the future.

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Effect of Organic Matter on the Flocculation of Colloidal Montmorillonite: A Modeling Approach

Cited by 21 publications

References 44 publications

Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions

Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions

The surface properties of Shewanella putrefaciens 200 and S. oneidensis MR-1: the effect of pH and terminal electron acceptors

An Approach to Modeling Biofilm Growth During the Flocculation of Suspended Cohesive Sediments

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