Study on the interaction properties between curdlan polysaccharide and water molecules in coal processing sludge by molecular dynamics simulation

The dehydrated chemical sludge has a strong water-holding capacity and is difficult to treat further and utilize. To explore the internal mechanism of sludge beam water, the molecular dynamics simulation method was used to study the interaction between Curdlan polysaccharide and water. The effects of water content, temperature, and chain number of polysaccharides on the binding capacity of polysaccharides were analyzed. The radial distribution function, number of hydrogen bonds, binding energy, etc., characterized the interaction properties. It was found that polysaccharides mainly use hydrogen bonding to bind water molecules, and the hydroxyl group connected to the main chain has the most vital binding capacity; the saturated water content of a single chain was 44.14%. The binding energy at different temperatures was also calculated. The results showed that 358 K was the critical point. When the temperature exceeds 358 K, the polysaccharide and water molecules turn from attraction to repulsion. At this time, polysaccharide molecules can no longer bind most of the water molecules in the system; the water molecules move more freely. Additionally, the increased number of polysaccharide chains will increase the interconnectedness to each other and wrap water molecules inside the polysaccharide molecules, then solidified water on the polysaccharide’s surface, enhancing the polysaccharide’s water bunching capacity.