Synthesis and properties of coal dust suppressant based on microalgae oil extraction

Abstract

Dust suppression is an important method for improving the effect of wet dust removal in coal mines. With the aim of overcoming the challenges of weak interfacial performance and the poor dust suppression effect caused by traditional coal dust suppressants under hard water conditions, a new method for extracting microalgae oil to synthesize coal dust suppressants is proposed here. The optimized conditions of microalgae oil extraction were analyzed by single-factor experiments and a response surface methodology. A microalgae oil-based coal dust suppressant (MODS) was synthesized from the extracted microalgae oil and its structure was determined. Property and performance tests were carried out under hard water conditions and the influence of hardness conditions on the dust reduction effect of the MODS was analyzed. The results show that a solvent ratio of 2.04:1, a liquor-to-material ratio of 4:1 and an extraction time of 4 h were the optimal extraction conditions for the microalgae oil. The MODS is an amide dust suppressant with an average tolerance of calcium concentration of 1271.28 mg·L−1, which had good resistance to hard water. Under the hard water conditions, the surface tension of the MODS remained at 31.8–33 mN·m−1 when the temperature, pH and salinity changed greatly (temperature of ≤60 °C, pH of 2–13 and NaCl mass fraction of ≤43 %). The dynamic contact angles of sodium dodecyl benzene sulphonate (SDBS) and the MODS at 60 s were 26.78° and 13.41°, respectively, and the sinking time of coal dust in the MODS solution was significantly smaller than that in the SDBS solution at the same concentration. This implied that the MODS performed better with regards to wettability than the commonly used anionic surfactant SDBS. This study lays an important foundation for the development of green and hardwater-resistant coal dust suppressants.