What is scale inhibitor and dispersant agent
Source: | Author:demihmain | Publish time: 2020-07-18 | 416 Views | Share:
some water treatment company do not know that What is scale inhibitor and dispersant agent
Scale inhibitor and dispersant are chemical agents which account for a large proportion in the daily chemical treatment of circulating water. For example, hydroxyethylenediphosphonic acid (HEDP) and aminotrimethylene phosphonic acid (ATMP) are all adsorbed on the active point of crystal (crystal nucleus) surface of scaling metal salts by electrostatic force, so as to keep many crystals in microcrystalline state, which is equivalent to increasing the amount of scaling metal salts in water At the same time, due to the adsorption of scale inhibitor molecules on the crystal surface, even if the crystal grows, it can only grow abnormally, which makes the crystal distorted. The adhesion between the distorted crystal and the metal surface is weakened, so it is not easy to deposit on the metal surface; because the functional groups adsorbed on the crystal surface are only part of the scale inhibitor molecules, the functional groups that do not participate in the adsorption will show ionic property to the crystal, and the crystal will be in a dispersed state due to the increase of the repulsive force of the charge. The above three effects exist at the same time, so that the amount of scale inhibitor needed to prevent the same amount of scaling metal salt from scaling on the metal surface in water is far less than the amount of chelating agent required to chelate the same amount of scaling metal salt in water to make it not precipitate. This phenomenon is called "threshold effect", also known as "low limit effect", or "sub stoichiometry effect". Therefore, they can disperse insoluble inorganic salts in water, prevent or interfere with the deposition and scaling of insoluble inorganic salts on the surface of metal equipment, maintain good heat transfer effect of metal equipment, and ensure normal production. Scale inhibitors mainly include some natural dispersants, phosphonic acid, phosphonic acid, phosphine sulfonic acid and polymer, and most of them are polymer.

The first scale inhibitor used in water treatment is about polyphosphate. Polyphosphate not only has scale inhibition effect, but also has corrosion inhibition effect. But its disadvantage is that it is easy to hydrolyze into orthophosphate. If it is not properly controlled, the problem of calcium carbonate scale which is not very serious will be transformed into a very serious problem of calcium phosphate scale. In the 1960s, the appearance of organic phosphate (salt) scale inhibitor shows that the scale inhibition technology of calcium carbonate in water has made a breakthrough progress. The ultra-low chromium treatment formula of circulating cooling water can also be applied. This ultra-low chromium formula is used in the pH range of 7.5-8.5. The application of high pH value reduces the requirement of chromate content from 15-25mg / L of traditional chromium phosphorus zinc formula to 5-10mg / L, which greatly reduces the adverse impact on the environment. The reason for this is that the application of organic phosphonic acid (salt) scale inhibitor can make calcium carbonate deposit in the cathode area of metal surface. This controlled deposition of calcium carbonate acts as a cathodic corrosion inhibitor. The application of organic phosphonic acid (salt) scale inhibitor also makes the classical phosphate organic phosphonic acid (salt) - polyacrylic acid (salt), a phosphorus series alkaline treatment formula, widely used in circulating cooling water. It is due to the appearance of scale inhibitor of calcium phosphate scale inhibitor that the phosphorus series alkaline treatment formula is further improved. For example, acrylic acid / methyl acrylate binary copolymer, acrylic acid / hydroxypropyl acrylate / methyl acrylate terpolymer, acrylic acid / acrylamide Methylpropane sulfonic acid / hypophosphite terpolymer, etc., are all developed to prevent calcium phosphate scale. If we say that up to now, there have been special scale inhibitors for calcium carbonate scale and calcium phosphate scale, there are not so effective scale inhibitors for magnesium calcium silicate, iron hydroxide, zinc hydroxide, calcium sulfate and barium sulfate scales, although many agents have shown scale inhibition effects on these scales.

At present, the research on scale inhibitor and dispersant concentrates on the development of various copolymers. And it is developing towards the preparation of a multi-functional water treatment agent. In addition, the development of environmentally friendly scale inhibitors in recent years has made contributions to the protection of the environment and water resources from pollution.