Potassium nitrate crystals can be separated from sand using one of the following set of processes. Identify which one?

Mixture of potassium nitrate and sand is added into a beaker of water, potassium nitrate dissolve in water and sand is insoluble in water. By filtration sand can be separated from mixture. After that by evaporation crystals of $KN{O}_3$  can be separated. These crystals can be purified by crystallization method.