5 research outputs found
Nanoparticle Flotation CollectorsThe Influence of Particle Softness
The ability of polymeric nanoparticles
to promote glass bead and pentlandite (Pn, nickel sulfide mineral)
attachment to air bubbles in flotation was measured as a function
of the nanoparticle glass transition temperature using six types of
nanoparticles based on styrene/N-butylacrylate copolymers. Nanoparticle
size, surface charge density, and hydrophobicity were approximately
constant over the series. The ability of the nanoparticles to promote
air bubble attachment and perform as flotation collectors was significantly
greater for softer nanoparticles. We propose that softer nanoparticles
were more firmly attached to the glass beads or mineral surface because
the softer particles had a greater glass/polymer contact areas and
thus stronger overall adhesion. The diameters of the contact areas
between polymeric nanoparticles and glass surfaces were estimated
with the Young–Laplace equation for soft, liquidlike particles,
whereas JKR adhesion theory was applied to the harder polystyrene
particles. The diameters of the contact areas were estimated to be
more than an order of magnitude greater for the soft particles compared
to harder polystyrene particles
Integrated ecological risk assessment of dioxin compounds
Current ecological risk assessment (ERA) schemes focus mainly on bioaccumulation and toxicity of pollutants in individual organisms. Ecological models are tools mainly used to assess ecological risks of pollutants to ecosystems, communities, and populations. Their main advantage is the relatively direct integration of the species sensitivity to organic pollutants, the fate and mechanism of action in the environment of toxicants, and life-history features of the individual organism of concern. To promote scientific consensus on ERA schemes, this review is intended to provide a guideline on short-term ERA involving dioxin chemicals and to identify key findings for exposure assessment based on policies of different agencies. It also presents possible adverse effects of dioxins on ecosystems, toxicity equivalence methodology, environmental fate and transport modeling, and development of stressor-response profiles for dioxin-like chemical