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The principle of polyacrylamide have four to down and learn knowledge on polyacrylamide compression of electric double layer, adsorption and charge neutralization and adsorption bridging action and sediment net trap machine the four kinds of the associated class.
1 sediment net catching mechanism: when the metal salt (such as aluminum sulfate or ferric chloride) or metal oxides and hydroxides (such as lime) as coagulating agent. When the dosage of added amount of large enough to rapid precipitation of metal hydroxides (such as Al (OH) 3, Fe (OH) 3, Mg (OH) 2 or carbon metal acid salt (such as CaCO3), the particles in the water can be these precipitates formed when net fishing. When sediment is positively charged (Al (OH) 3 and Fe (OH) 3 in the neutral and acidic pH range, the precipitation rate can be accelerated by the presence of anions in solution, such as silver sulfate ion. In addition the water particles itself as the metal oxygen oxide precipitates formed the core, so the condensation agent is the best investment quantity and removed the concentration of a substance is inversely proportional, namely more particles, metal condensation agent investment plus the amount of the less.
2 compression of electric double layer: electric double layer structure of micelle decided in colloidal particles at the surface anti ion density is the biggest, with the distance from the particle surface outward more counter ion concentration is lower, the final and the concentration of the ions in the solution are equal. When the electrolyte is added to the solution, the concentration of the ion in the solution increases and the thickness of the diffusion layer decreases. When two particles are close to each other, due to the thickness of diffusion layer decreases, the potential decreases, so they are mutually exclusive force decreases, also is the repulsion force between the adhesive with a higher concentration of ions in the solution ion concentration ratio of low to small. Suction between colloidal particles from aqueous phase composition, but due to the diffusion layer thinning, they collided distance decreases. Such a mutual attraction. Visible the repulsive and attractive force by the repulsion mainly into by suction (repulsive potential energy disappeared), the particles can quickly gather, this mechanism can better explain the harbor deposition phenomenon, because of fresh water into the sea, the salts increased, the ion concentration increased, fresh water entrainment micelle stability decreased, so in the harbor of clay and other colloidal particles to deposit.
3 adsorption and charge neutralization: adsorption and charge neutralization effect refers to the particle surface of opposite sign ions, different number of particles or chain from the molecular band heterocharge parts have a strong adsorption, due to the adsorption and part of its charge, reducing the electrostatic repulsion, thus easily and the particles are close to each other and adsorption. At this point, the electrostatic force is often the main aspects of these effects, but in many cases, the other is more than the electrostatic force. For example, with Na removal with negatively charged silver iodide solution, causing turbidity were with dodecyl ammonium ions (C12H25NH3 ), found that with the destabilization of the monovalent organic amine ion capacity is much larger than Na , Na excessive dosage will not cause colloidal stability again, and organic amine ion is not however exceeds a certain cast when can make the colloidal stabilization phenomenon and that colloidal particles adsorbed on the over the counter ions, so that the original negative charge in the transition into positively charged. Aluminum salt, ferric salt dosage is also more stable and variable charge phenomenon. It is appropriate to explain the mechanism of adsorption and neutralization.
4 adsorption bridging action: the mechanism of adsorption bridging action mainly refers to the macromolecule substance and colloid adsorption and bridging. Can be understood as two large particles with intermediate due to a different number of colloidal particles together. Polymer flocculant with linear structure, they have certain parts of the particle surface and the role of chemical groups, when the high polymer and colloidal particle contact. Groups can produce special reaction and the colloidal particle surface and the mutual adsorption, and the rest of the polymer molecule is extended in solution, and another surface space of adsorbed particles, this polymer is the bridge connecting role. If less particles and the polymer extension Exhibition adhesion with the second particle, the extension sooner or later will be the original colloidal particles adsorbed on the other parts of the, the polymer is not a bridging role in the and colloidal particles in steady state. The polymer flocculant dosage is too large, will make the particle surface saturation and stability. Have bridging flocculation of colloidal particles, such as by mixing of intense for a long time, bridging polymers may be uncoupled from the other particles surface, heavy and rollback to the original location of particle surface, resulting in stable state. Polymer particle surface sources in the adsorption in various physical and chemical processes, such as van der Waals force, electrostatic, hydrogen bonding, coordination bond, depending on the polymer particle surface chemical structure characteristics. This mechanism can explain the phenomenon of good flocculation effect of nonionic or ionic polymer with the same number.