Mechanism of accelerated dissolution of mineral crystals by cavitation erosion

Cavitation, a phenomenon produced by a moving fluid, is ubiquitous in the water environment of the Earth's surface and its related mechanical action in the process of cavitation leads to the widespread erosion of rock in nature. Although the mechanical action of flowing water body that accelerates the rock mass loss and fragmentation of rock (abrasion, erosion, and etching) and other phenomena have been much studied, its acceleration of mineral crystal dissolution is rarely reported. The physical mechanism of effect is not yet clear. The cavitation bubble produced in the cavitation process is at the micron level, and its related mechanical action leading to the accumulation of rock mineral dissolution is manifested in time and space in the process of the chemical element's migration between water and rock minerals. Cavitation erosion may be one of the important driving forces for the migration of geochemical elements within the lithosphere and hydrosphere. In this paper, based on the crystal dissolution stepwave dynamic theory and the theoretical derivation and calculation of Gibbs free energy change of the mineral crystals plastic deformation which caused by the mechanical action of cavitation erosion, we give the possible mechanism of accelerating the transient dissolution of mineral crystals by cavitation erosion-the cavitation bubbles on the surface of the near crystal release the high speed micro-jet and shock wave perpendicular to the surface during the collapsing, in which the water hammer pressure produced by micro-jet at the solid-liquid interface causes instantaneous plastic deformation on the crystal surface under the condition that it is larger than the yield stress of the crystal. Under the influence of the thermal effect of the plastic deformation process and the change of Gibbs free energy (the dislocation elastic strain energy of plastic deformation on the crystal surface may be included), the local instantaneous dissolution rate of the mineral surface is accelerated. The continuous cavitation erosion eventually causes fracture and breaking of the mineral crystal, meanwhile, the Gibbs-Thomson effect may enhance the dissolution of mineral crystals more prominently. At the same time, the correctness of the mechanism is verified qualitatively by the acoustic cavitation experiment with the same erosion mechanism.