Polymeric scale inhibitors include homopolymers and copolymers
.
Homopolymers mainly include sodium polyacrylate (PAA), polymethacrylic acid (PMA), polyaspartic acid (PASP), etc.
There are many types of copolymers, and monomers with different functional groups and their different composition ratios can be used.
It forms a series of binary, ternary and quaternary copolymers with various functional groups
.
The scale inhibition mechanism of copolymer scale inhibitors can be roughly divided into the following three ways
.
① After the chelating and solubilizing copolymer scale inhibitor is dissolved in water, groups such as carboxyl group, hydroxyl group and phosphoric acid group can dissociate hydrogen ions, turning them into negatively charged anions.
These negative ions interact with Ca 2+ , Mg 2+ Plasma metal ions form stable complexes, thereby increasing the supersaturation during precipitation of Ca crystal grains, that is, increasing the solubility of CaCO 3 in water
.
②The effect of lattice distortion during the growth of calcium carbonate crystallites, when scale inhibitors are added, they will adsorb to the active growth point of calcium carbonate crystals and integrate with Ca 2+ , inhibiting the growth of the crystal lattice in a certain direction, and make the crystals grow in a certain direction.
Distorted
.
This is also the mechanism that produces the critical value effect
.
In addition, some of the compounds adsorbed on the crystals are drawn into the crystal lattice as the falling crystals grow, causing the CaCO 3 lattice to be dislocated, forming some cavities in the scale layer, and reducing the interaction between molecules, making it harder.
The scale becomes soft
.
③Condensation and subsequent dispersion.
For polycarboxylate scale inhibitors, they dissociate in water to form carboxylate-containing ions.
When they collide with calcium carbonate crystallites, physical and chemical adsorption will occur, causing the surface of the crystallites to form a double electric Layer
.
The chain structure of the polycarboxylate can adsorb multiple crystallites of the same charge, and the electrostatic repulsion between them can prevent the crystallites from colliding with each other, thereby avoiding the formation of crystals
.
When the adsorption product encounters other polycarboxylate ions, it will transfer the adsorbed crystals, resulting in a uniform dispersion of crystal grains
.
This prevents the collision between the crystal grains and between the crystal grains and the metal surface, reduces the number of crystal nuclei in the solution, and stabilizes the calcium carbonate in the aqueous solution
.
As a water treatment agent, copolymer scale inhibitors have the advantages of a wide range of varieties, mature synthesis methods, wide applicable water quality range, low toxicity and no pollution, etc.
, and are a class of green scale inhibitors with great development prospects
.
Copolymer scale inhibitors have broad research, development and application prospects in China
.
