Jonathan Brant

Centre Européen de Recherche et d’Enseignement des Géosciences de l’Environnement, Aix, Provence-Alpes-Côte d'Azur, France

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Publications (18)52.3 Total impact

  • Jérôme Labille, Jonathan Brant
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    ABSTRACT: Aqueous systems represent a likely carrier for manufactured nanoparticles upon their introduction into the natural environment. Their behavior in water, and in turn the risk that is posed by these materials to environmental and human communities, is a top concern. In terms of risk assessment, nanoparticle exposure to organisms is largely driven by their dispersion and behavior in aqueous systems, while their potential hazard, although not always well understood, is often related to their surface speciation. Both of these characteristics arise from the reactions that occur at the solid/liquid interface. The objective of this article is to establish the current state of the science with regard to the possible changes in surface properties and/or behavior of manufactured nanoparticles in different aqueous solutions of model and inorganic composition. The general reactions occurring at the nanoparticle/water interface, or between nanoparticles themselves, are first introduced. Following this, metal oxides, pure metals and carbon nanoparticles are considered on a case-by-case basis.
    Nanomedicine 08/2010; 5(6):985-98. · 5.26 Impact Factor
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    ABSTRACT: The nature of fullerene-water interactions and the role that they play in the fate of C60 in aqueous systems is poorly understood. This work provides spectroscopic evidence for the surface hydroxylation of the initially hydrophobic C60 molecule when immersed in water. This mechanism appears to be the basis for stabilizing the hydrophilic nC60 aggregates in suspension. It is remarkable that such a chemical transformation and dispersion are achieved under mild conditions that are readily produced in an aquatic environment. This acquired affinity for water is likely to play a subsequent role in the reactivity, mobility, and bioavailability of fullerenes in aqueous media.
    Langmuir 10/2009; 25(19):11232-5. · 4.38 Impact Factor
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    ABSTRACT: a b s t r a c t The objective of this research was to evaluate a select number of promising surface treatments for mak-ing ceramic membranes hydrophobic and suitable for application in direct contact membrane distillation (DCMD). Alumina anodisc TM membranes were made hydrophobic through surface treatments that uti-lized perfluorodecyltriethoxysilane, trimethylchlorosilane, or trichloromethylsilane. The effectiveness of each surface treatment in modifying the membrane surface chemistry was assessed using contact angle measurements with water, scanning electron microscopy (SEM), infrared adsorption, and atomic force microscopy (AFM). Contact angle measurements with water showed that both perfluorodecyltriethoxysi-lane and trichloromethylsilane produced membrane surfaces with sufficiently high hydrophobicity and thus, suitably high pore entry pressures, for application of the membranes in DCMD. The perfluorode-cyltriethoxysilane treated anodisc TM had a higher steady-state water flux than the trimethylchlorosilane treated anodisc TM . Furthermore, this membrane had a 20% higher flux relative to a polymeric TF-200 membrane under similar test conditions. The superior performance of the anodisc TM is attributed to the more optimized pore structure and geometry relative to that which typifies most polymeric membranes used in DCMD.
    Journal of Membrane Science 01/2009; 331:1-10. · 4.09 Impact Factor
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    ABSTRACT: Here we report on the characteristics of fullerol in aqueous systems and examine those conditions that affect the physical state of fullerol in water. When dispersed in water fullerol forms polydisperse suspensions characterized by both small ( approximately 100 nm) and large associations (>500 nm). These clusters are charged with a point of zero net proton charge (PZNPC) of approximately pH 3. Though the size of fullerol clusters may be manipulated through changes in solution chemistry, principally pH, cluster formation cannot be entirely prevented through these means alone. The fullerol cluster structure is amorphous as revealed by X-ray diffraction analysis, which is in contrast to clusters of C(60) formed through dissolution in toluene and then introduced into water through sonication (SONnC(60)). The SONnC(60) clusters are crystalline with a structure similar to that of unreacted C(60) crystals.
    Journal of Colloid and Interface Science 11/2007; 314(1):281-8. · 3.17 Impact Factor
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    ABSTRACT: Truckee Meadows Water Reclamation Facility TMWRF is a 150,000 m3/day 40 mgd tertiary wastewater treatment facility that serves the cities of Reno and Sparks, Nev. The effluent from TMWRF is discharged into the Truckee River which flows to Pyramid Lake—a very sensitive ecosystem and habitat for endangered species. Reverse osmosis RO and nanofiltration NF, in conjunction with ultrafiltration UF pretreatment, were evaluated for total dissolved solids TDS and nutrient removal from the effluent of TMWRF at bench and pilot scale. Results from short-term pilot-scale tests showed that RO and NF membrane processes can successfully remove both TDS and nutrients from the effluent when paired with coagulation-enhanced UF pretreatment. NF membranes were able to achieve the necessary removal while maintaining higher fluxes and lower specific power consumption.
    Journal of Environmental Engineering-asce - J ENVIRON ENG-ASCE. 01/2007; 133(12).
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    ABSTRACT: Nanomaterial properties differ from those bulk materials of the same composition, allowing them to execute novel activities. A possible downside of these capabilities is harmful interactions with biological systems, with the potential to generate toxicity. An approach to assess the safety of nanomaterials is urgently required. We compared the cellular effects of ambient ultrafine particles with manufactured titanium dioxide (TiO2), carbon black, fullerol, and polystyrene (PS) nanoparticles (NPs). The study was conducted in a phagocytic cell line (RAW 264.7) that is representative of a lung target for NPs. Physicochemical characterization of the NPs showed a dramatic change in their state of aggregation, dispersibility, and charge during transfer from a buffered aqueous solution to cell culture medium. Particles differed with respect to cellular uptake, subcellular localization, and ability to catalyze the production of reactive oxygen species (ROS) under biotic and abiotic conditions. Spontaneous ROS production was compared by using an ROS quencher (furfuryl alcohol) as well as an NADPH peroxidase bioelectrode platform. Among the particles tested, ambient ultrafine particles (UFPs) and cationic PS nanospheres were capable of inducing cellular ROS production, GSH depletion, and toxic oxidative stress. This toxicity involves mitochondrial injury through increased calcium uptake and structural organellar damage. Although active under abiotic conditions, TiO2 and fullerol did not induce toxic oxidative stress. While increased TNF-alpha production could be seen to accompany UFP-induced oxidant injury, cationic PS nanospheres induced mitochondrial damage and cell death without inflammation. In summary, we demonstrate that ROS generation and oxidative stress are a valid test paradigm to compare NP toxicity. Although not all materials have electronic configurations or surface properties to allow spontaneous ROS generation, particle interactions with cellular components are capable of generating oxidative stress.
    Nano Letters 09/2006; 6(8):1794-807. · 13.03 Impact Factor
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    ABSTRACT: In this paper, vertical scanning interferometry (VSI) and atomic force microscopy (AFM) were used to characterize the topography of several nanofiltration and reverse osmosis membrane surfaces. Comparing roughness results from the two different characterization techniques revealed unique results for the various membrane surfaces. Roughness values tended to be higher from the interferometry measurements compared to those from AFM measurements for the same membranes. This was attributed to the inability of the AFM to capture dramatic changes in surface height of several microns or more. Based on interferometric measurements surface roughness was also found to increase with increasing scan-size up to a scan-size of 250,000 μm2 after which it remained relatively constant. Because such large scan-sizes are too large to be captured through AFM measurements interferometry appears to provide a more comprehensive characterization of membrane surface roughness.
    Journal of Membrane Science 07/2006; 278:410-417. · 4.09 Impact Factor
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    ABSTRACT: We examined the physical and chemical characteristics of colloidal dispersions of fullerene materials (nC60) produced through several solvent exchange processes and through extended mixing in water only. The nC60 produced via the different methods were unique from each other with respect to size, morphology, charge, and hydrophobicity. The greatest dissimilarities were observed between the nC60 produced by extended mixing in water alone and the nC60 produced by solvent exchange processes. The role of the respective solvents in determining the characteristics of the various nC60 were attributed to differences in the solvent-C60 interactions and the presence of the solvent as a residual in the nC60 structure, indicating the significance of the solvent properties in determining the ultimate characteristics of the colloidal fullerene. Thus, fullerene C60 that may become mobilized through natural processes (agitation in water) may behave in dramatically different ways than those produced through more artificial means. These results highlight the difficulties in generalizing nC60 properties, particularly as they vary in potential toxicity considerations.
    Langmuir 05/2006; 22(8):3878-85. · 4.38 Impact Factor
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    ABSTRACT: In this work, we have studied the affinity of pure C-60 fullerenes with water. Although C-60 have always been known as hydrophobic particles, we show that this characteristic does not remain when contact between C-60 and H2O is forced by mechanical stirring. Light scattering measurements and transmission electron microscopy observations revealed the presence of C-60 aggregates remaining stable in water after stirring, with a large nanometric size range. Water adsorption/desorption isotherms, confirmed the hydrophilic character of these nano-clusters, resulting form hydration of the initial hydrophobic C-60.
    Fullerenes Nanotubes and Carbon Nanostructures 04/2006; 14(2-3):307-314. · 0.76 Impact Factor
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    Jonathan A. Brant, Kelly M. Johnson, Amy E. Childress
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    ABSTRACT: In this investigation, two methods for characterizing membrane surface potential are investigated. Results from atomic force microscopy (AFM) analyses are compared with streaming potential measurements. In calculating surface potential from AFM force measurements, assumptions of constant charge and constant potential were both considered for modeling electrostatic interactions. For a ceramic mica surface, the constant charge assumption was found to be most appropriate while for a polymeric membrane surface, the constant potential assumption provided results that agreed better with theoretical expectations. For both the mica and membrane surfaces, results from AFM agreed with the measured values determined from streaming potential analysis. The advantage of AFM is that in addition to determining the mean surface potential value for membrane surfaces, this technique provides a spatially resolved measure of charge distribution. One drawback of the technique is that it is sensitive to surface roughness, as the measured charge distribution increased with increasing surface roughness.
    Journal of Membrane Science. 01/2006;
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    Jonathan A Brant, Kelly M Johnson, Amy E Childress
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    ABSTRACT: Chemical force microscopy (CFM) was used to characterize the chemical heterogeneity of two commercially available nanofiltration and reverse osmosis membranes. CFM probes were modified with three different terminal functionalities: methyl (CH 3), carboxyl (COOH), and hydroxyl (OH). Chemically distinct information about the membrane surfaces was deduced based on differences in adhesion between the CFM probes and the membrane surfaces using both traditional atomic force microscopy (AFM) force measurements and spatially resolved friction images. Contact angle titration and streaming potential measurements provided general information about surface chemistry and potential, which largely complemented the CFM analyses, but could not match the accuracy of CFM on the atomic level. Using CFM it was found that both membranes were characterized as chemically heterogeneous. Specifically, membrane chemical heterogeneity became more significant as the scan size approached colloidal or micron-sized dimensions. In many instances, the chemically unique regions, contributing to the overall chemical heterogeneity of the membrane surface, were substantially different in chemistry (e.g., hydrophobicity) from that determined for the surface at large from contact angel and streaming potential analyses. Topographical and corresponding CFM images supports previous adhesion studies finding a correlation between surface roughness and the magnitude of adhesion measured with AFM. However, chemical specificity was also significant and in turn measurable with CFM. The implication of these findings for future membrane development is discussed.
    Aspects. 01/2006; 280:45-57.
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    ABSTRACT: In this study we report on the electrokinetic behavior of colloidal aggregates of C60fullerenes (n-C60) produced through two different techniques: solvent exchange and extended mixing with water. In the first technique, used to produce colloidal materials in several recent toxicity and transport studies, an organic solvent such as tetrahydrofuran (THF) is used to dissolve the C60 before mixing with water. The second technique is more indicative of conditions that might occur in natural aquatic systems. Both types of n-C60 were observed to be negatively charged under a variety of solution chemistries; however, the n-C60 formed using THF was more strongly charged. We conclude that n-C60 likely acquires charge through charge transfer from the organic solvent (when present) and surface hydrolysis reactions. Nevertheless, C60 is capable of acquiring charge and becoming dispersed as n-C60 in water without the aid of organic solvents, a pathway that may be important in determining the mobility of fullerenes in natural systems. These findings also show that n-C60 made using THF retains a portion of the solvent in the cluster structure, subsequently influencing the characteristics of the n-C60 and possibly requiring a re-interpretation of results from recent studies on n-C60 toxicity using THF-derived materials.
    Environmental Science and Technology 10/2005; 39(17):6343-51. · 5.26 Impact Factor
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    ABSTRACT: The propensity of n-C60 to aggregate and deposit will play a key role in determining its longevity in aquatic systems, and therefore the potential exposure and risk presented by these colloids. We consider the origin of n-C60 stability and compare the aggregation and deposition characteristics of n-C60 under conditions of variable ionic strength using an indifferent electrolyte. Relatively weak electrolyte solutions (0.001M) were observed to destabilize suspensions of n-C60 resulting in the formation of settleable aggregates. This behavior supports the hypothesis that the stabilizing mechanism for n-C60 clusters is electrostatic in origin. Similarly, the deposition of n-C60 in porous media increased as ionic strength increased. These observations suggest that under some conditions present in natural aquatic systems, these materials may have limited mobility as they form large aggregates that may settle out of suspension or deposit on surfaces. These phenomena may, at least partially, offset any risk presented by n-C60 toxicity due to a reduced potential for exposure.
    Journal of Nanoparticle Research 09/2005; 7(4):545-553. · 2.18 Impact Factor
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    Sarah K. Dalton, Jonathan A. Brant, Mark R. Wiesner
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    ABSTRACT: This work considers the hypothesis that the association of trace-level hydrophobic organic compounds with dissolved organic matter (DOM), similar to macromolecular materials found in natural water systems, may influence the contaminant's ability to permeate across synthetic membranes. A batch dialysis system using semipermeable membranes in conjunction with a model lipid phase was used to explore the impact of systematic changes in solution-chemistry on the permeability of four low-molecular weight organic compounds (LMWOCs) of environmental concern: cyclonite, atrazine, naphthalene, and 2,4-dichlorophenol. Similar to previous studies, no correlation could be drawn between molecular weight and contaminant permeability across the membrane for the four LMWOCs. However, contaminant transport was observed to depend on the polarity and hydrophobicity of the LMWOCs. Moreover, the interactions between the organic compounds and DOM varied as a function of solution chemistry (i.e., pH and divalent electrolyte concentration). These results demonstrate considerable variability in the importance and the underlying mechanisms of interactions that may occur between LMWOCs and natural organic matter during membrane separations.
    Journal of Membrane Science. 01/2005;
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    Jonathan A. Brant, Amy E. Childress
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    ABSTRACT: Colloidal adhesion to membrane surfaces is an important parameter in determining membrane fouling propensity and in optimizing membrane cleaning strategies. It has previously been demonstrated that acid–base interactions can significantly affect colloid–membrane interaction as a colloid approaches a membrane surface, however, the effect of acid–base interactions on adhesion has received less attention. In this investigation, the approach and adhesion of a silica and polystyrene colloid was measured on three commercially available hydrophilic water treatment membranes using an atomic force microscope and the colloid probe technique. It was found that the hydrophobic polystyrene colloid adhered more weakly to each membrane compared to the hydrophilic silica colloid. These results could not be resolved through classic DLVO analysis alone and were in direct contrast to the expected interaction based on the strong hydrophobic character of the polystyrene colloid. However, the results could be explained by considering the magnitude of the surface’s electron-acceptor (γ+) and electron-donor (γ−) components. It is hypothesized that through hydrogen bonding with surface γ+ and γ− groups, structured water layers exist to varying extents at the surfaces of the silica colloid and the hydrophilic membranes, and that their removal results in the formation of strong adhesive bonds between reciprocal γ+ and γ− groups. Furthermore, even when surface roughness is substantial, γ+ and γ− groups appear to play some role in determining the magnitude of the measured adhesion. The lack of such groups on the polystyrene colloid, and thus the lack of hydrogen bonding capacity, was responsible for its weaker adhesion with the membranes.
    Journal of Membrane Science. 10/2004;
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    ABSTRACT: A tool for the study of biological adhesion forces with the atomic force microscope (AFM) is introduced. The tool, a “microplatform,” can be functionalized with variety of specimens such as bacterial cells and used to study adhesion between the specimen and a surface. This tool is easily created using commercially available silicon AFM tips and an AFM, and can be customized in size to fit specific applications. Two custom fabricated microplatforms, ∼1 and ∼2.5 μm were tested. The method of microplatform fabrication, as well as adhesion force data between E. coli bacteria and a nanofiltration membrane is presented. © 2003 American Institute of Physics.
    Review of Scientific Instruments 09/2003; 74(10):4491-4494. · 1.60 Impact Factor
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    Jonathan A Brant, Amy E Childress
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    ABSTRACT: Theoretical predictions of interaction energies for several membrane–colloid pairs were made using the classical DLVO theory and an extended DLVO (XDLVO) approach. The XDLVO approach accounts for acid-base (polar) interactions that are not considered in the classical DLVO theory. For all membrane-colloid pairs studied, DLVO interactions were similar. However, inclusion of acid-base interactions re-sulted in substantially different predictions of short-range (separation distance ,10 nm) interaction ener-gies for several of the membrane–colloid pairs investigated. Predicted interaction energies were compared with atomic force microscopy (AFM) force measurements. The colloid probe technique was used to di-rectly measure the force of interaction between a single colloid and a membrane surface. It was found that for strongly hydrophilic systems where the XDLVO approach predicts substantially different inter-action energies than the DLVO theory, the measured force curves agree with the interaction sequence pre-dicted by the XDLVO approach. For strongly hydrophobic systems where the XDLVO approach predicts an interaction similar to that predicted by the DLVO theory, the measured force curves agree with the in-teraction sequence seen in both DLVO and XDLVO predictions. It was also found that because the mem-branes have much higher surface energies (primarily due to the acid-base component) than the colloids investigated, the membranes control the general behavior of the interactions.
    Environmental Engineering Science - ENVIRON ENG SCI. 01/2002; 19(6).
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    Jonathan A. Brant, Amy E. Childress
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    ABSTRACT: The contribution of acid–base (AB) (polar) interactions to the total interaction energy between membranes and colloids was investigated. The surface energetics of several membranes and colloids were evaluated using the Lifshitz–van der Waals acid-base approach. This provides the van der Waals (LW) and polar interaction energies between various surfaces from measurements of contact angles of different probe liquids on these surfaces. In addition, the surface potentials of the membranes and colloids were determined using electrokinetic measurements, yielding the electrostatic (EL) interaction between these surfaces. The three interaction energy components (LW, EL, and AB) were combined according to the extended Derjaguin–Landau–Verwey–Overbeek (extended DLVO or XDLVO) approach to evaluate membrane–colloid interaction energies. Predictions of interaction energy based on the XDLVO approach were compared to the corresponding predictions from the classical DLVO theory. For all the membrane–colloid combinations studied, the DLVO potentials were quite similar. However, inclusion of AB interactions resulted in a substantially different (qualitative and quantitative) prediction of short-range (separation distances <5 nm) interaction energies for several of the membrane–colloid combinations investigated. Finally, all of the membranes studied were found to have substantially low surface energies compared to the colloids and the interaction energy between the membranes and colloids was primarily dictated by the surface energies of the colloids. Fouling experiments for a membrane and three colloids supported the fouling trends predicted by the XDLVO approach.
    Journal of Membrane Science 01/2002; · 4.09 Impact Factor

Publication Stats

999 Citations
52.30 Total Impact Points

Institutions

  • 2010
    • Centre Européen de Recherche et d’Enseignement des Géosciences de l’Environnement
      Aix, Provence-Alpes-Côte d'Azur, France
  • 2009
    • University of Wyoming
      • Department of Civil and Architectural Engineering
      Laramie, WY, United States
  • 2007
    • Duke University
      • Department of Civil and Environmental Engineering (CEE)
      Durham, NC, United States
  • 2005–2006
    • Rice University
      • Department of Civil and Environmental Engineering
      Houston, TX, United States
  • 2002–2004
    • University of Nevada, Reno
      • • Department of Civil and Environmental Engineering
      • • Department of Mechanical Engineering
      Reno, NV, United States