There are several factors that can cause a decrease in the rate of dissolution:
Decrease in temperature: As the temperature decreases, the kinetic energy of the particles decreases, and the rate of dissolution also decreases.
Increase in solute concentration: If the solution is already saturated with solute, then adding more solute will cause it to become supersaturated, which can cause a decrease in the rate of dissolution.
Increase in pressure: Increasing the pressure can force more solute into the solution, but it can also cause an increase in the solubility of the solute, which can cause a decrease in the rate of dissolution.
Decrease in surface area: If the solute is in the form of large particles, then breaking it down into smaller particles will increase the surface area available for dissolution and increase the rate of dissolution. Conversely, decreasing the surface area will decrease the rate of dissolution.
Formation of a precipitate: If the solute is capable of forming a precipitate in the solution, then the rate of dissolution may decrease as the solute is removed from the solution and deposited as a solid.
~~~Harsha~~~