Forward osmosis is also called osmosis, it refers to water or other solvent separated from natural or man-made, transfer from low to high solute concentration side side solute concentration, and it is a physical phenomenon widely exists in the nature.
Forward osmosis (Forward osmosis FO) technology is a new membrane concentration developed in recent years, driven by the separation technology, it relies on the selective permeation osmosis membrane on both sides of the differential pressure as the driving force to achieve the spontaneous water transfer membrane separation process, and it is one of the hot spots in the present world in the field of membrane separation.
The forward osmosis process does not require additional pressure, and the water molecules can be extracted from the raw water side of the low osmotic pressure through the semi permeable membrane, moreover, the other solutes in the raw water are retained, and then other processes are used to separate the water from the diluted liquid. Finally, pure water is obtained, and the liquid can be recycled. The driving force of the flow of water molecules from low concentration side to high concentration is the difference of osmotic pressure on both sides of the semi permeable membrane.
The forward osmosis membrane is usually made up of the activation layer and support layer. When the raw water flows through the side of the activation layer, the osmotic pressure is much higher than that of the raw water, and it flows through the side of the support layer of the forward osmosis membrane. The water molecules spontaneously flow from the raw water side by side and draw on the liquid side, because the positive osmosis membrane has the interception effect on the salt and other pollutants in raw water, the solute in raw water is condensed, while the leaching solution is diluted by water molecules in the forward osmosis membrane.
Ammonia and carbon dioxide gas mixture has high solubility in water. The resulting liquid can generate huge osmotic pressure driving force to permeate the water molecules through the membrane, even though the total dissolved solids (TDS) of the raw water with high salinity is as high as 200000 mg/L. The diluted solution can be recycled by heating and decomposing the solute, and the energy needed to decompose the solute in the solution is lower than that of the latent heat of water evaporation.
After decomposition, ammonia and carbon dioxide gas are reclaimed through condensation, and then dissolved into the extraction solution for reuse. The water dissolved is a relatively pure water production after ammonia and carbon dioxide is removed.
The technology of forward osmosis membrane is derived from the reverse osmosis technology, compared with the reverse osmosis technology, the positive osmosis technology has unique advantages:
The unique drive system does not require external pressure to push the separation process, and the energy consumption is low;
The material itself is hydrophilic, without the push of pressure, which can effectively prevent membrane fouling;
In the process of desalting, the recovery rate is high, no concentrated brine is discharged, and zero discharge is realized. It is an environmentally friendly technology.
Until now, forward osmotic technology has not only been applied in the field of seawater desalination, but also has been applied to the fields of water purification, waste-water treatment, food and medicine.
Forward penetration test equipment is mainly used for experimental research and teaching demonstration of forward osmosis. It can also be used for seawater desalination,
Treatment of high salt waste water, High COD waste water treatment, treatment of ammonia waste liquid, concentration of sludge digestion liquid and treatment of Landfill Leachate, etc..
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