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Introduction to Reverse Osmosis Membrane Systems a) Overview and Working Principle of Reverse Osmosis Membranes Reverse osmosis is a liquid-liquid separation method in which, under the influence of a pressure difference, salts and small molecules pass through the reverse osmosis membrane while larger molecules are retained. It is primarily used for the concentration and purification of large molecules in solutions. Reverse osmosis systems mostly use cross-flow filtration. The cross-flow method prevents clogging that occurs during end-filtering: the liquid flow passes over the surface of the membrane, and under pressure, liquids and small molecules pass through the membrane, while insoluble substances and large molecules are retained ； The feed stream has a sufficient flow rate to strip away the substances trapped by the membrane from its surface; this continuous stripping reduces membrane fouling, thereby allowing a high membrane permeation flux to be maintained over an extended period of time. Cross-flow filtration has proven to be the most effective, reliable, and cost-efficient membrane separation method. The cross-flow process also avoids the need to rely on a filter cake layer for filtration during dead-end filtration processes (such as plate and frame filter presses or drum vacuum filters); separation takes place on the surface of the membrane rather than within the filter cake layer, thereby ensuring that the quality of the filtrate remains uniform and stable throughout the process. The quality of the filtrate depends on the membrane itself, keeping the production process under complete effective control. b) Structure of spiral-wound reverse osmosis membranes: Spiral-wound reverse osmosis membrane modules have a simple design and high packing density. Their internal structure consists of multiple \"membrane pockets\" wrapped around a porous central tube; the three sides of each membrane pocket are sealed, while the fourth side is sealed to the porous central tube. A permeate flow channel is formed within these membrane pockets using a porous support material. A mesh-like material forms a flow channel for the material fluid between the membrane bags; the material fluid flows parallel to the central collection tube. The permeate that enters the membrane bags moves in a rotational direction toward the central collection tube, from where it exits. c) Application areas of reverse osmosis membranes 3.1 Water treatment: By utilizing the charged nature of the membrane surface, high-valent ions can be removed while allowing monovalent ions to pass through. It is applied to water softening and advanced treatment of drinking water, and the safe drinking water produced possesses biological activity. 3.2 Wastewater treatment: Combined with biochemical methods, it enables the reuse of reclaimed water, wastewater, and sewage, as well as the recovery of chemicals. Such as alkali recovery from papermaking wastewater ； Decolorization of dye wastewater, etc. 3.3 Concentration and purification of chemical and pharmaceutical products; concentration and purification of dye products; concentration and purification of polysaccharide products; concentration and purification of antibiotics and synthetic drugs. d) Advantages of reverse osmosis membranes for the concentration and purification of products. 4.1 The only driving force for the operation of the system is pressure, resulting in extremely low energy consumption ； 4.2 The membrane has a wide range of tolerance conditions and a high concentration factor ； 4.3 The equipment has a simple and compact structure, is very easy to operate, and enables automated operation ； Concentration at room temperature, without destroying the active ingredients of the product; low loss rate and high recovery rate ；