Agglomeration is a phenomenon,fingerSolstaystatic electricityParticle aggregation and sedimentation under the action.[2]Add to colloidelectrolyte solutionAddedcation(oranion）Neutralizes the charge carried by the colloidal particles, making the colloidal particles aggregate into larger particles, thus forming precipitation fromDispersion systemIn the precipitation.
Chinese name
Coalescence precipitation
Foreign name
Coagulation
Sediment clot
Sediment clot
Floc
floc
External conditions
Adding electrolyte, colloid with opposite charge, heating
Definition
Colloidal particles aggregate into larger particles and then precipitate
Coalescence precipitation[1]。The reason why the colloid is stable is that the colloidal particles have the same charge and repel each other, and the colloidal particles are irregularBrownian motionIt also makes the colloidal particles stable.Therefore, the principle of colloid agglomeration is to neutralize the charge of colloidal particles or accelerate theThermal movementSo as to increase the binding opportunity of colloidal particles.
influence factor
Announce
edit
influenceSolThere are many factors for stability, such aselectrolyteThe interaction of colloid and so on.
（1）SolyeselectrolyteIt is very sensitive, and a small amount of electrolyte can cause sol agglomeration, usually usingCoalescence valueTo indicate the ability of electrolyte to agglomerate.Coagulation value is the electrolyte concentration just enough to cause a certain sol agglomeration under certain conditions, generally expressed in mmol/L.
The ability of the electrolyte to agglomerate is mainly determined by the valence of the ion with the opposite sign (with the charged sign of the particle).The higher the ionic valence, the greater the ability of the electrolyte to agglomerate.
①Schulze Hardy valence rule: The ability of coalescence is mainly determined by the ionic valence of electrolyte with opposite charge to the colloidal particlesCounterionThe ratio of its coagulation value is about 100:1.6:0.14, about (1/1): (1/2): (1/3), that is, the coagulation value is inversely proportional to the sixth power of the counter ion valence.
② The ability of ion agglomeration is different with the same valence.For example, some univalent positiveion pairThe agglomeration ability of negative sol can be arranged in the following order: H+>Cs+>Rb+>NHfour+>K+>Na+>Li+, but different priceanionJustificationSolThe aggregation and sedimentation capacity of is in the following order: F->Cl->Br->NOthree->I->SCN->OH-。
③ Same numberion pairAgglomeration also has an impact, because the strongVan der WaalsThe adsorption is generated, which changes the surface properties of the colloidal particles and reduces theCounterionThe ability of agglomeration and sedimentation.
2) Colloid interaction will mix the colloids with opposite charges, and agglomeration will also occur.AndelectrolyteThe difference of the agglomeration effect of the two sols is that the amount of the two sols should be just enough toCharge quantityWhen they are equal, they will be completely agglomerated, otherwise they may not be completely agglomerated, or even not.
The colloid with opposite charge can also be addedelectrolyteThe same effect makes the colloid agglomerate.IfFe(OH)3Colloid additionSilicic acidIn colloids, both colloids will agglomerate.
3) When the colloid is heated, the energy increases, the movement of colloidal particles intensifies, and the chances of collision between them increase, which makes the colloidal nucleusAdsorptionWeakening, that is, it weakens the stability factor of the colloid, leading to colloid agglomeration.
Long term heating, Fe (OH)threeThe colloid will coagulate to form reddish brown precipitate.
Add to the solutionelectrolyte, which increases theTotal concentrationHowever, it creates favorable conditions for charged colloidal particles to attract oppositely charged ions, thus reducing or neutralizing the charge of the original colloidal particles and making them lose the factor of maintaining stability.At this time, due to theBrownian motionWhen they collide with each other, they can gather and settle quickly.
When salt is added to the colloid, the cation or anion in it can neutralizeDispersantThe charge carried by the particles makes the dispersed matter gather into larger particles and form precipitation under the action of gravity.This phenomenon of colloid precipitation is called colloid agglomeration (applicable toHydrosol）。
If usedSoybean MilkWhen making tofu, add CaSO at a certain temperaturefour(or otherselectrolyte solution）The charge of colloidal particles in soymilk is neutralized, and the particles in soymilk quickly gather to formJellyShaped tofu (called gel).
Generally speaking, when electrolytes are added, the high valence ions are more efficient than the low valence ions to agglomerate the colloid.For example, agglomeration capacity:
The addition of colloidal particles with opposite charges can also play the same role as the addition of electrolyte to make the colloid agglomerate.
Such as Fe (OH)threeColloid additionSilicic acidIn colloids, both colloids will agglomerate.
heating
When the colloid is heated, the energy increases, the movement of colloidal particles intensifies, and the chances of collision between them increase, which makes the colloidal nucleusAdsorptionWeakening, that is, it weakens the stability factor of the colloid, leading to colloid agglomeration.
If heated for a long time, Fe (OH)threeThe colloid will coagulate to form reddish brown precipitate.
Life application
Announce
edit
Jellied tofu
When making tofu from soybean milk, add CaSO at a certain temperaturefour(or otherselectrolyte solution）The charge of colloidal particles in soymilk is neutralized, and the particles in soymilk quickly gather to formJellyShaped tofu (called gel).
