Molecular-level explanation of interactions of random and block polycarboxylic acid dispersants with bituminous coal in coal–water slurry through experiments and simulations

Abstract

The adsorption conformations of random-structure polycarboxylic acid (PCR) and block-structure polycarboxylic acid (PCB) on coal surfaces were analyzed from a microscopic perspective. This analysis involved a combination of molecular dynamics (MD) simulations and experiments. The saturation adsorption amount of PCB was found to be significantly much larger than that of PCR. Additionally, observations from the contact angle and X-ray photoelectron spectroscopy confirmed that PCB exhibited superior wetting performance on coal compared to PCR and had a greater adsorption layer thickness. The relative concentration changes and the mean square displacement (MSD) of water indicate that the better adsorption of PCB on the coal surface makes the water molecules more evenly distributed, which improves hydration, increases the thickness of the “adsorption layer”, and enhances the mobility of water molecules. The interaction energy suggests the block structure of PCB is more favorable for molecular extension due to its well-defined structure. This provides a theoretical and experimental basis for expanding the molecular sequence structure design of polycarboxylic acid dispersants.