Views: 8 Author: Site Editor Publish Time: 2022-08-12 Origin: Site
Desalinated water refers to the finished water obtained after removing impurities in water such as suspended matter, colloids and inorganic cations and anions using various water treatment processes.Desalted water does not mean that all the salts in the water are removed. For technical reasons and due to the cost of water production, desalted water is allowed to contain trace impurities according to different applications. The less impurities in demineralized water, the higher the water purity.
Desalinated water contains little or no minerals, and this can be done by distillation, reverse osmosis, ion exchange or a combination of these methods.
Brine is heated so that the water in it turns into steam, and then the steam is allowed to condense down. Since the salts dissolved in the brine do not come out with the steam, the resulting water is distilled water that is nearly pure. However, both heating and condensation consume energy. Every 1 gram of water evaporated requires 2.3 kJ of energy. So this method is fine for emergencies, but it is not a long-term solution.
The salts dissolved in water are in the form of cations and anions. If there is something that can remove these ions, then the water will be purified. Ion exchange resins have the ability to do just that. An ion exchange resin is a water-insoluble polymer with a reticulated structure. It is like a large tree with many branches, each with a pocket in it. When salt water passes through, the cations exchange out the hydrogen ions in the "pockets" of the cation exchange resin, and the anions exchange out the hydroxide ions in the "pockets" of the anion exchange resin, and the hydrogen ions and hydroxide ions meet and become water.
The method of making fresh water from seawater by reverse osmosis is also called "membrane technology". The key to this process is the reverse osmosis membrane. The membrane has to be strong because firstly the process is pressurized; secondly it has to be 100% selective so that only water can pass through and no other chemicals can pass through; and finally it should have a large throughput to speed up the preparation process.