What factors affect the rate of dialysis?

Dialysis is a separation technique that works using selective and passive diffusion through a semipermeable membrane. The rate of dialysis is determined by the same factors that affect the rate of diffusion of a molecule. These factors include: 

• Temperature: An increase in temperature affects the thermodynamics of molecules, speeding up the rate of diffusion. Hence, dialysis proceeds faster at room temperature compared to the rate at 4°C. However, when determining the optimal temperature, it is important to factor in the thermal stability of the molecule of interest. 
• Concentration of the molecule: The rate of diffusion is directly proportional to the concentration of the molecule. The higher the concentration, the faster the rate of diffusion. This is because, as the concentration of a molecule increases, the likelihood of it making contact with the dialysis membrane and diffusing across to the other side also increases.
• Molecular weight of the molecule: The rate of diffusion is inversely proportional to its molecular weight. As the molecular weight increases, the rate of movement in solution slows down considerably. This reduces its chances of diffusion across the membrane even if it is small enough to pass through the pores.
• Membrane surface area and thickness: The rate of dialysis is directly proportional to the surface area of the membrane – the larger the surface area, the faster the rate of diffusion and dialysis. However, the dialysis rate is inversely proportional to its thickness – the thicker the membrane, the slower the rate of diffusion and dialysis.