Molecular Mechanisms by Which Linear Versus Branched Alkyl Chains in Nonionic Surfactants Govern the Wettability of Long-Flame Coal

Improving the wettability of coal dust with nonionic surfactants is crucial for mitigating environmental pollution. Here we compare two nonionic surfactants with distinct architectures—n-octyl-α-D-glucoside (OG) and Isooctyl glucoside (APG08)—to dissect how linear versus branched C8 chains govern the wetting of long-flame bituminous coal dust. Sedimentation and contact-angle measurements show that the linear OG, with reduced steric hindrance, assembles into a denser interfacial layer and delivers superior wetting. Corroborating spectroscopic and microscopic analyses (FTIR, XPS, and SEM) reveal that OG treatment increases hydroxyl functionalities and the O-element fraction at the coal surface; OG also drives stronger particle aggregation, consistent with markedly enhanced adsorption on coal. Molecular dynamics simulations further indicate tighter OG adsorption, a more homogeneous coal–water interfacial structure, and stronger binding of water to OG-modified surfaces. Collectively, these results identify chain linearity as a key design lever for nonionic glucosides and establish OG as a more effective wettability promoter for long-flame coal dust.