Which method of separation uses a barrier that only allows certain particles to pass through?

Filtration is the method of separation that utilizes a barrier, such as a filter paper or a membrane, designed to allow specific particles or liquids to pass through while trapping larger particles, such as solids. This technique is particularly effective for separating mixtures, such as sand from water, where the solid particles cannot pass through the filter, while the liquid can. The size of the pores in the filter determines what can pass through; smaller particles or dissolved substances can move freely, while larger particles are retained, effectively achieving separation based on size.

Though there are several other methods of separation mentioned, they operate on different principles. Magnetic separation relies on the magnetic properties of certain materials, centrifugation uses the principle of density and centrifugal force, and chromatography separates substances based on their different rates of movement through a stationary phase. These methods do not involve a simple barrier for selective passage of particles in the same way that filtration does.