Development and characterization of a high efficiency bio-based rhamnolipid compound dust suppressant for coal dust pollution control.

Surfactants make a significant contribution to the suppression of coal dust fly in underground coal mines, but are hazardous to the environment and human health. It is therefore crucial to develop more environmentally friendly and efficient wetting agents using non-polluting eco-friendly surfactants. In this study, the wetting properties of the biosurfactant rhamnolipid were investigated and the rhamnolipid composite wetting agent (CS-A-S) was prepared by mixing design after preferring different surfactants by means of experiments and quantum mechanical simulations. The dust suppression properties were compared by means of infrared spectroscopy, scanning electron microscopy and molecular dynamics simulation. The results showed that the critical micelle concentration (CMC) of rhamnolipid was 0.04 wt% and the surface tension was 25.9 mN/m, which had the basis to become an underground dust suppressant; the surface tension of CS-A-S was reduced to 23.95 mN/m and the contact angle to coal dust was 25°; after spraying CS-A-S, the median particle size of coal dust reached 125.76 μm, an increase of 849.13%; the specific surface area was reduced to 2.24 m/g, a decrease of 51.06%; the oxygen-containing groups on the coal surface increased by 55.87-246.7%, making it easier to form hydrogen bonds, the coal dust became more hydrophilic, and coal dust particles easily agglomerated into larger sizes and settled rapidly under gravity; the CS-A-S simulated system showed the greatest degree of water molecule penetration, with a minimum of 71 Å, and a water molecule diffusion coefficient of 1.06 Å/ps, a decrease of 75%, and the interaction energy with coal molecules is 155.6 kcal/mol, an increase of 66.9%, making it easier for the dust suppressant molecules to form adsorption on the coal surface, showing a better dust suppression effect.