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.
Group of Environmental Physical Chemistry, F.-A. Forel Institute, University of Geneva, 10 route de Suisse, 1290 Versoix, Switzerland.
Sci Total Environ. 2015 Nov 1;532:556-63. doi: 10.1016/j.scitotenv.2015.05.134. Epub 2015 Jun 20.
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.
赤铁矿纳米粒子的物理化学特性与其尺寸、表面积和反应性有关，这使得它们在许多应用中非常有用，同时也是研究聚集动力学的合适模型。对于许多应用（例如受污染地下水的修复），保持赤铁矿纳米粒子悬浮液的稳定性至关重要，以确保它们到达目标地点。使用生物聚合物已被提议作为一种避免纳米粒子聚集并确保其稳定性的合适的环保选择。本工作的目的是研究赤铁矿纳米粒子与从 Prosopis ruscifolia 获得的非常规半乳甘露聚糖（角豆胶--VG）之间形成复合物，以促进赤铁矿纳米粒子用绿色生物聚合物进行涂层。研究了赤铁矿纳米粒子、VG 分散体的zeta 电位和它们混合物的稳定性，以及生物聚合物浓度和制备方法的影响。使用 DLS 和纳米颗粒跟踪分析技术来确定悬浮液的尺寸和 zeta 电位。VG 显示出多分散的尺寸分布（300-475nm Z-平均直径，0.65 Pdi）和负的 zeta 电位（在 pH2 和 12 时分别为-1 到-12 mV）。在低于 2mg/L（pH5.5）的浓度下，VG 的加入会导致赤铁矿纳米粒子（3.3mg/L）聚集。另一方面，在高于 2mg/L 的 VG 浓度下，赤铁矿纳米粒子得到稳定。赤铁矿纳米粒子和 VG 之间涉及几种现象：空间位阻效应、静电相互作用、电荷中和、电荷反转和聚合物桥接。赤铁矿纳米粒子与生物聚合物之间的络合过程强烈受到制备方案的影响。研究结果表明，赤铁矿纳米粒子的聚集、分散和稳定性取决于生物聚合物的浓度，也取决于制备方法和初始水相的物理化学性质。
