How does dialysis remove dissolved salts from protein solutions?

In chemistry, dialysis removes dissolved salts from protein solutions by utilizing the difference in particle size and diffusion rates through a semipermeable membrane.1

The process involves placing the protein solution into a sac made of a semipermeable material, such as cellulose or acetylcellulose. This membrane contains pores that are small enough to prevent large protein molecules from passing through, while allowing smaller molecules, such as dissolved ions and salts, to diffuse out.21

When the sac is immersed in water or a salt solution, the dissolved salts move from the area of higher concentration (inside the sac) to the area of lower concentration (outside the sac) via diffusion. Because the protein molecules are too large to penetrate the membrane, they remain trapped inside the sac, effectively separating them from the unwanted salts. This is a gradual process that can be accelerated by heating or, in the case of charged particles, by applying an electric field (electrodialysis).132