1 research outputs found
Role of Humic Acid in Enhancing Dissolved Air Flotation for the Removal of TiO<sub>2</sub> Nanoparticles
The particle separation efficiency
by flotation sharply decreases
or even completely fails when the diameter of dispersed particles
falls into the nanoscale. In the present laboratory work, humic acid
was used to enhance the removal of TiO<sub>2</sub> nanoparticles from
suspension in a chemical coagulant-free dissolved air flotation process.
Without humic acid, merely 63.8% of TiO<sub>2</sub> nanoparticles
were removed. For the humic acid-assisted dissolved air flotation,
the pH of humic acid solution significantly influenced the removal
efficiency: more than 90% of nanoparticles could be separated when
the pH of the humic acid stock solution was acidic; however, the basic
solutions resulted in rather poor performance. In the acidic solution,
the fiberlike humic acid might form colloids through the attraction
between hydrophobic moieties. They possibly acted as a fishnet and
trapped nanoparticles, leading to the great measured bubble–particle
attachment efficiency. In all the effluents, a low residual dissolved
organic carbon was observed, revealing a good participation of humic
acid in flotation. Moreover, a higher air-to-solid ratio could improve
the nanoparticle elimination by offering a larger surface area of
air bubbles. The fractal dimension of flotation flocs demonstrated
that the aggregates with compact structure took greater advantage
in the flotation separation of nanoparticles