Effects of salt ions and deposit formation on the permeation of organic molecules in complex media in reverse osmosis

Salt ions significantly reduce the rate of permeation of lactose in the reverse osmosis of a salt containing lactose solution compared with the permeation from a pure lactose solution under identical experimental conditions. The reason for this is thought to be the displacement of uncharged molecules from the boundary layer in front of the membrane by charged ions, which accumulate at the membrane surface due to their strong forces of interaction. In addition, deposited layers of protein from milk, starch and gelatine reduce the rate of permeation both of lactose and of salt ions. This is thought to be due to the compression of the region of the deposited layer adjacent to the membrane into a secondary membrane with solution diffusion properties.