title: Formation of complexes between hematite nanoparticles and a non-conventional galactomannan gum. Toward a better understanding on interaction processes.
abstract: The physicochemical characteristics of hematite nanoparticles related to their size, surface area and reactivity make them useful for many applications, as well as suitable models to study aggregation kinetics. For several applications (such as remediation of contaminated groundwater) it is crucial to maintain the stability of hematite nanoparticle suspensions in order to assure their arrival to the target place. The use of biopolymers has been proposed as a suitable environmentally friendly option to avoid nanoparticle aggregation and assure their stability. The aim of the present work was to investigate the formation of complexes between hematite nanoparticles and a non-conventional galactomannan (vinal gum--VG) obtained from Prosopis ruscifolia in order to promote hematite nanoparticle coating with a green biopolymer. Zeta potential and size of hematite nanoparticles, VG dispersions and the stability of their mixtures were investigated, as well as the influence of the biopolymer concentration and preparation method. DLS and nanoparticle tracking analysis techniques were used for determining the size and the zeta-potential of the suspensions. VG showed a polydispersed size distribution (300-475 nm Z-average diameter, 0.65 Pdi) and a negative zeta potential (between -1 and -12 mV for pH2 and 12, respectively). The aggregation of hematite nanoparticles (3.3 mg/L) was induced by the addition of VG at lower concentrations than 2mg/L (pH5.5). On the other hand, hematite nanoparticles were stabilized at concentrations of VG higher than 2 mg/L. Several phenomena between hematite nanoparticles and VG were involved: steric effects, electrostatic interactions, charge neutralization, charge inversion and polymer bridging. The process of complexation between hematite nanoparticles and the biopolymer was strongly influenced by the preparation protocols. It was concluded that the aggregation, dispersion, and stability of hematite nanoparticles depended on biopolymer concentration and also on the way of preparation and initial physicochemical properties of the aqueous system.
authors.affiliation: Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Ciudad Universitaria, C1428EGA Ciudad Autónoma de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Verónica M
authors.initials: VM
authors.lastname: Busch
authors.affiliation: Group of Environmental Physical Chemistry, F.-A. Forel Institute, University of Geneva, 10 route de Suisse, 1290 Versoix, Switzerland.
authors.forename: Fréderic
authors.initials: F
authors.lastname: Loosli
authors.affiliation: Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Ciudad Universitaria, C1428EGA Ciudad Autónoma de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Patricio R
authors.initials: PR
authors.lastname: Santagapita
authors.affiliation: Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Ciudad Universitaria, C1428EGA Ciudad Autónoma de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: M Pilar
authors.initials: MP
authors.lastname: Buera
authors.affiliation: Group of Environmental Physical Chemistry, F.-A. Forel Institute, University of Geneva, 10 route de Suisse, 1290 Versoix, Switzerland. Electronic address: serge.stoll@unige.ch.
authors.forename: Serge
authors.initials: S
authors.lastname: Stoll
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D005690:Galactose / Q000031:analogs & derivatives; D007700:Kinetics; D008351:Mannans / Q000737:chemistry*; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D055672:Static Electricity
chemical_list: D005290:Ferric Compounds; D008351:Mannans; C012990:galactomannan; C000499:ferric oxide; D005690:Galactose
keywords: Aggregation kinetics; Hematite nanoparticles; Iron oxides; Polymer–nanoparticle interaction; Vinal gum