Mixed
surfactants have a prominent synergistic effect and show
advantages in many aspects. In this work, the effects of a mixture
of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate
(SDS) on the flotation of low-rank coal were studied from the wetting
rate, contact angle, surface tension, and zeta potential. Furthermore,
the adsorption configuration of the mixed surfactant on the surface
of oxygen-containing graphite was simulated at the molecular level
by molecular dynamics simulation. The experimental results show that
the combustible matter recovery of low-rank coal flotation is improved
using the mixed surfactant, and the contact angle test and wetting
rate test confirmed the synergistic effect of the mixed surfactant.
In the mixed surfactant system, the addition of SDS with an opposite
charge to DTAB can reduce the mutual repulsion between DTAB molecules
and enhance the degree of DTAB alignment in solution, which was analyzed
by surface tension and zeta potential tests. Meanwhile, the simulation
results reveal the adsorption behavior of anionic and cationic surfactants
on the surface of oxygen-containing graphite from the molecular level
and also verify the experimental results. This investigation provides
a good understanding of the interaction mechanism of mixed surfactants
in low-rank coal flotation.