Kinetics and activation energy of solvent swelling of coal altered by an ultrasonication-enhanced process

We studied the kinetics and activation energy of solvent swelling in Qinyuan and Xiongshan coal in perchloroethylene (PCE) using conventional and ultrasonication-enhanced treatment conditions. Kinetic parameters suggested that both coal types exhibited anomalous diffusion regardless of treatment conditions. However, the kinetic parameter n, an exponent that crudely indicates the nature of the solvent diffusion process, decreased with the addition of ultrasound in both coal types. We suggest this change is due to the greater diffusion of PCE into coal during ultrasonication based on greater relaxation of the coal macromolecular network and microscopic agitation of the liquid solvent. Activation energy of coal solvent swelling decreased for both coal types with the addition of sonication, indicating that the energy barrier for the process was reduced in the presence of ultrasound.