Design of Biodegradability-Qualified Surfactant Dust Suppressant for Ultrafine Oil-Rich Coal Dust Guided by Wettability

Ultrafine coal dust is difficult to capture with water because its small size promotes suspension while hydrophobic surface domains hinder droplet spreading. Due to its unique surface properties and chemical environment, the effectiveness of conventional dust suppressants is often unsatisfactory for oil-rich coal dust. This study designed a low-dose anionic–nonionic surfactant dust suppressant for ball-milled Hongliulin coal dust by integrating wettability screening, laboratory dust-suppression testing, biodegradability screening, and spectroscopic characterization. The median particle diameter (D50) was 5.89 μm. The surface energy calculated using the Owens two-liquid method was 63.32 mJ m−2 ± 0.3 mJ m−2, including dispersive and polar components of 33.17 and 30.15 mN m−1, respectively. Sodium secondary alkane sulfonate (SAS-60) and Methyl ester sulfonate (MES) were combined separately with Coconut diethanolamide (CDEA) and Alkyl polyglucoside (APG) at mass ratios of 1:3, 2:2, and 3:1. Contact angle, surface tension, and Draves-type settling-rate results were used to select three candidate formulations. In the laboratory chamber, CDEA: SAS-60 = 3:1 at a total mass fraction of 0.20% delivered the highest dust-reduction efficiency (70%), compared with approximately 30% for water. The BOD5 (biochemical oxygen demand)/COD (chemical oxygen demand) ratios of the three candidates were all above 0.40. FTIR peak fitting showed that, relative to water treatment, the areas assigned to –OH and Ar–C–O increased from 4.50 to 5.87 A·cm−1 and from 0.13 to 0.18 A·cm−1, respectively. The results identify CDEA: SAS-60 (3:1, 0.20%) as a promising low-dose, biodegradability-qualified formulation for this coal sample and provide an experimentally grounded basis for tailoring wetting-type suppressants to ultrafine coal dust.