Aggregation of Titanium Dioxide Nanoparticles: Role of a Fulvic Acid

Abstract

The increasing use of nanomaterials in consumer products has led to increased concerns about their potential environmental and health impacts. To better understand the transport, fate, and behavior of nanoparticles in aquatic systems, it is essential to understand their interactions with different components of natural waters including natural organic matter over a broad range of physicochemical conditions. Fluorescence correlation spectroscopy was used to determine the diffusion coefficients of TiO2 nanoparticles having a nominal size of 5 nm. The effects of a various concentrations of the Suwannee River Fulvic Acid (SRFA) and the roles of pH and ionic strength were evaluated. Aggregation of the bare TiO2 nanoparticles increased for pH values near the zero point of charge. At any given pH, an increase in ionic strength generally resulted in increased aggregation. Furthermore, conditions which favored adsorption of the SRFA resulted in less aggregation of the TiO2 nanoparticles, presumably due to increased steric repulsion. Under the conditions studied here, nanoparticle dispersions were often stable for environmentally relevant conditions of SRFA, pH, and ionic strength, suggesting that in the natural environment, TiO2 dispersion might occur to a greater extent than expected.

Antibacterial activity of silver nanoparticles: A surface science insight

“…This DOM is constituted mostly of aromatic and aliphatic hydrocarbon structure that exhibit amide, carboxyl, hydroxyl, ketones and various minor functions [129]. In an optic of standardization, most studies internationally are performed using DOM (or purified humic acid or fulvic acid fractions) obtained from the Suwannee River [130][131][132]. These fractions have been shown to adsorb at the surface of nanoparticles, causing their aggregation [130,133] and limiting their Ag + release [97].…”

Heteroaggregation of nanoparticles with biocolloids and geocolloids

“…Naturally occurring colloids are ubiquitous in natural surface water and are likely to affect the aggregation and sedimentation of NPs [39]. Natural colloids include [40][41][42][43]: (1) compact inorganic colloids; (2) large and rigid biopolymers (0.1-1 μm); and (3) soil-derived fulvic compounds (few nanometers) or their equivalent in pelagic waters, aquagenic refractory organic matter. In general, the concentration of NPs is expected to be much lower than naturally occurring colloids [44].…”

“…The importance of NOM on the aggregation behavior of nanoparticles has led to many studies. However, due to the complex composition of NOM, most of the studies consider a specific composition of NOM, such as fulvic acid [43] or humic acid, and more recently, microbial EPS [58,[87][88][89]. In addition, although a number of studies have provided a clear understanding of the role of NOM in a homoaggregation system [14,80,90], there are very few studies that address the role of NOM in heteroaggregation [91].…”

Removal of TiO2 Nanoparticles During Primary Water Treatment: Role of Coagulant Type, Dose, and Nanoparticle Concentration

“…As such, NPs are considered emerging pollutants that have the capacity to enter and impact water supplies. Thus, it is of critical importance to understand the movement of nanomaterials (Domingos et al, 2009) in various model aquatic environments (Zhang et al, 2008) and determine how they can be most effectively removed through conventional water treatment processes. This is of concern since nanoscale TiO 2 have been reported to cause adverse effects such as oxidative stress in human cells (Long et al, 2006;Xia et al, 2008) and genetic instabilities in mice (Trouiller et al, 2009).…”