What is poly aluminum chloride (PAC) ?
Poly Aluminum Chloride, also known as Hydrated Aluminum Chloride (ACH) or Pack (PAC), has a special place as a polymer and mineral coagulant in drinking water treatment, wastewater treatment. It has urban, agricultural and industrial effluents. Poly aluminum chloride is an inorganic coagulant and forms stable compounds with many organic and inorganic materials.
In the past, aluminum sulfate (alum) and Chlorophyll were used as coagulants in water treatment to remove turbidity, but now poly aluminum chloride is a suitable alternative to these two coagulants in the market. Poly aluminum chloride is known and used in countries such as the United States, China, Canada, France, the United Kingdom and other countries as one of the most common coagulants in the treatment of water, wastewater and industrial effluents. Is a substitute for many coagulants in water and wastewater treatment.
Types of poly aluminum chloride (PAC):
If we want to divide the pack, you see that it is marketed in the following two grades:
Industrial Aluminum Chloride (Sewage)
Oral or beverage (sanitary) poly aluminum chloride
Analysis of polyaluminum chloride types
| PAC DRINKABLE | PAC industrial |
Production process of poly aluminum chloride:
Industrial production of poly aluminum chloride is done by chemical reaction between alumina hydrate powder with hydrochloric acid at a certain temperature and pressure. In this process, a certain amount of hydrochloric acid with a concentration of between 15 and 30% with a certain amount of aluminum hydroxide is mixed together with a mixer and the output liquid is transferred into the reactor to perform the reaction under a certain pressure and temperature.
After the reaction, the output product is transferred to the dilution tanks and the unreacted hydrated aluminum chloride is separated by filtration and sent into the fermentation tank, where after adding water with the chemical and mixture to adjust the required concentration, The final product is sent to storage tanks.
Mechanism of action of poly aluminum chloride:
The pack acts as a coagulant. It is used for flocculation, turbidity removal, reduction of water TDS, or effluent of colloid. This is done by adsorbing on the surface of colloidal particles and creating a bridge between the particle, the polymer and the particle. The mechanism of the pack is such that by producing hydroxyl ions and polyvalent anionic polymers, it causes the formation of heavy flakes and large inorganic macromolecules, which are the same as clots, in water. This mechanism increases the rate of particle destabilization and the rate at which colloids settle. As a result, separation and settling are done better and faster. Its pH range is between 5 and 9. Consumption of the pack reduces the organic impurities in the water. Poly aluminum chloride has a different and more effective performance compared to older coagulants. Aluminum chloride performs the destabilization process by adsorbing colloidal particles and creating particle-polymer-particle bridges. This remarkable property increases the rate of instability, rapid particle growth and ultimately improves the particle separation process and water and wastewater treatment. To be.
If this product is used effectively in the water and wastewater treatment process, it can bring the amount of organic and inorganic substances suspended in the water below the standard level. Colloids are very small and suspended particles that will not be separated from water by natural methods due to their light weight and stability. These particles cause turbidity in water. These particles can be: clay, sludge , Viruses, bacteria as well as some organic materials including asbestos, radioactive particles and silicates.
Removal of these colloidal particles is of great importance because they can cause pathogens and harmful to humans. One of the most common coagulants used in Iran is aluminum salts such as poly aluminum chloride to remove water turbidity. Its high impact, cost-effectiveness and availability have been suggested as a common product in water and wastewater treatment. Another advantage of water and wastewater treatment is the presence of chlorine in its formulation, high antibacterial properties and its use in a wide range of pH.
Application of poly aluminum chloride (PAC):
Water and effluent treatment returned from factories
Drinking water purifier
Municipal and industrial wastewater treatment
To regenerate coal from its washing effluent
Preparation of dough in cellulose industries
In separation in oil and gas and petrochemical industries
In the textile, leather and leather industries
To reduce the amount of oxygen COD
In the food industry b to prevent the formation of micelles
In the process of refining sugar
As a catalyst carrier in chemical processes
In the construction industry for fast coagulation of cement
In the cosmetics industry for the preparation of cosmetics
To make chemicals
How to use poly aluminum chloride:
To benefit from the best results of using poly aluminum chloride, it should be used in cold water with a higher pH (more alkaline) and should not be mixed with other chemicals. After dilution, it should be used and its consumption is between 1 to 15 kg per ton, the exact amount of consumption varies depending on its analysis and use.
Performance of poly aluminum chloride in water treatment:
One of the prominent features of poly aluminum chloride in its performance is the stable neutralization of colloidal particles, which creates suitable conditions for chemical coagulation of particles and ultimately the instability of colloidal particles. Once the material is in good condition to stabilize the suspended particles, while the solution is slowly stirring, the time required for the particles to coagulate and eventually flocculation is provided.
Finally, as water passes through the sedimentation pond, the solid particles clot and are separated by sedimentation. The performance range of poly aluminum chloride at pH is between 5 and 9 and the most suitable performance range is pH between 6.5 to 7.6 (neutral pH). By forming hydroxyl ions and polyvalent anionic polymers, this substance causes the formation of electrically inorganic molecules and macromolecules in water, resulting in the coagulation and flocculation of suspended particles.
Coagulation process by poly aluminum chloride:
Poly aluminum chloride performs the coagulation process by its two main mechanisms, including entrapping in sedimentary and neutral clots and stabilizing the electric charge. It also hydrolyzes rapidly in water and produces different cationic compounds that can cause adsorption. Compounds are negatively charged and neutralize them, thereby destroying the stability of these particles.
Using the right amount in this process is key, if used incorrectly in this process will cause the particles to re-charge and their instability and also increase the sludge formed.
Poly aluminum chloride initially stabilizes colloidal particles and, by bonding them together, causes micro clots to form. At this stage, a flocculating agent such as polyelectrolytes are added to the water to bind these small clots together to provide sediment conditions.
Influence of PH on water treatment process by poly aluminum chloride:
Due to the fact that in the coagulation process, any coagulant, including poly aluminum chloride, is within a certain range of pH, pH control is of particular importance. Studies on pH have shown that the proper pH significantly removes contaminants and the appropriate range to improve the performance of poly aluminum chloride is between 5 and 7.
The importance of controlling the pH level is important because in use above the standard level, it can be dangerous to human health and also contain amounts of chemical residues. In fact, excessive consumption of this substance causes poor performance in the flocculation process.
