Dissolution-diffusion model:
In the first step, the solute and the solvent are adsorbed and dissolved outside the liquid-liquid side surface of the inner membrane of the glass fiber reinforced plastic membrane shell; in the second step, there is no interaction between the solute and the solvent, and they are passed through in a molecular diffusion manner driven by the respective chemical potential Active layer of reverse osmosis membrane; in the third step, solutes and solvents are desorbed on the permeate side of the inner membrane of the glass fiber reinforced fiberglass membrane housings.
In the process of the above solute and solvent penetrating the inner membrane of the glass fiber reinforced plastic membrane shell, it is generally assumed that the first and third steps are performed very quickly. At this time, the transmission rate depends on the second step, that is, the Driven through the membrane by molecular diffusion. Due to the selectivity of the inner membrane of the glass fiber reinforced plastic membrane shell, the gas mixture or liquid mixture can be separated. The permeability of a substance depends not only on the diffusion coefficient, but also on its solubility in the inner membrane of the glass fiber reinforced plastic membrane shell.
Priority adsorption-capillary flow theory:
When different kinds of substances are dissolved in a liquid, its surface tension will change differently. For example, alcohol, acid, aldehyde, lipid and other organic substances are dissolved in water, which can reduce its surface tension, but dissolve some inorganic salts, but increase its surface tension slightly, because the solute is not uniformly dispersed. That is, the concentration of the solute in the surface layer of the solution is different from the concentration inside the solution, which is the phenomenon of surface adsorption of the solution. When the aqueous solution is in contact with the polymer porous membrane, if the chemical properties of the inner membrane of the glass fiber reinforced plastic membrane shell make the inner membrane of the glass fiber reinforced plastic membrane shell negatively adsorb the solute and preferentially adsorb water, the interface between the inner membrane and the solution of the glass steel membrane shell A layer of pure water with a certain thickness is absorbed by the inner membrane of the FRP membrane housings. Under the action of external pressure, it will pass through the pores on the inner membrane surface of the glass fiber reinforced plastic membrane shell, so that pure water can be obtained.
Hydrogen bonding theory:
In cellulose acetate, due to the effects of hydrogen bonding and van der Waals force, there are two parts of the crystalline phase region and the amorphous phase region in the film. The crystalline phase region exists between the macromolecules that are firmly bound and arranged in parallel, while the amorphous phase region is completely disordered between the macromolecules. Water and solutes cannot enter the crystalline phase region. Near the cellulose acetate molecule, water forms oxygen bonds with the oxygen atoms on the cellulose acetate carbonyl group and forms what is known as bound water. When cellulose acetate adsorbs the first layer of water molecules, it will cause the entropy of water molecules to drop greatly, forming a structure similar to ice. In the large pore space of the amorphous phase region, the share of bound water is very low. There is water of ordinary structure in the center of the pore, and ions or molecules that cannot form hydrogen bonds with the cellulose acetate membrane in the glass fiber reinforced plastic membrane shell enter the binding Water, which migrates in an orderly manner, passes through the inner membrane of the high pressure FRP membrane housing by continuously changing the position of the hydrogen bonds with cellulose acetate.
FRP Membrane Housing
Under the action of pressure, the water molecules in the solution and the activation point of the cellulose acetate-oxygen atoms on the carbonyl group form hydrogen bonds, and the hydrogen bonds formed by the original water molecules are broken, and the water molecules dissociate and move to The next activation point forms a new hydrogen bond, so through a series of hydrogen bonds formation and disconnection, water molecules leave the dense active layer on the inner membrane surface of the glass fiber reinforced plastic membrane shell and enter the porous layer of the membrane. Because the porous layer contains a large amount of capillary water, water molecules can flow out of the inner membrane of the glass fiber reinforced plastic membrane shell.
