Formation of complexes between hematite nanoparticles and a non-conventional galactomannan gum. Toward a better understanding on interaction processes

BUSCH, MARÍA VERÓNICA; LOOSLI, FRÉDERIC; SANTAGAPITA, PATRICIO R.; BUERA, M. PILAR; STOLL, SERGE

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 532 p. 556 - 563

0048-9697

The physicochemical characteristics of hematite nanoparticles related to their size, surface area and reactivity make themuseful for many applications, aswell 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 proposedas a suitable environmentally friendly option to avoid nanoparticle aggregation and assure their stability. The aimof the present workwas to investigate the formation of complexes between hematite nanoparticles anda 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 dispersionsand 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 determiningthe 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 pH 2and 12, respectively). The aggregation of hematite nanoparticles (3.3 mg/L) was induced by the addition of VG at lower concentrations than 2 mg/L (pH 5.5). On the other hand, hematite nanoparticles were stabilized atconcentrations 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. Theprocess 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 nanoparticlesdepended on biopolymer concentration and also on the way of preparation and initial physicochemical properties of the aqueous system.