Cationic polyacrylamide is a versatile polymer widely used in wastewater treatment due to its effective flocculation properties, particularly for organic colloids, enhancing sedimentation and clarity in various industrial applications.
What is Cationic polyacrylamide?
Cationic polyacrylamide is a kind of linear high molecular polymer, with kinds of active groups, forming a hydrogen bond. absorbent with may substance.mainly flocculate colloids with negative charge,with the performance of excepting turbidity and decoloring, adsorption, adhesion and other functions, it is suitable for wastewater treatment with high organic colloid cotent,like dyeing, papermaking, food, building, metallurgy, mineral processing, coal, oilfield, aquatic products processing and fermentation lines, it is especially suitable for the city wastewater, city sewage sludge, papermaking sludge and other industrial sludge treatment.
- Appearance:white powder
- Solid content:89%
- Molecular weight:6-14million
- Insoluble matter≤0.5%
- Residual monomer≤0.05%
- Dissolving time: ≤60mins
Application of Cationic polyacrylamide
Cationic polyacrylamide is an effective flocculant for treating organic wastewater and domestic sewage, particularly in acidic or alkaline conditions. Its positive charge enhances flocculation, sedimentation, and clarity, especially in wastewater with negatively charged suspended particles. It significantly outperforms anionic and nonionic polyacrylamide in high organic content wastewater, such as that from alcohol production, papermaking, and dyeing. Additionally, it is cost-effective for treating tap water sourced from rivers, yielding better results when combined with inorganic flocculants. This potent flocculant is utilized in water treatment facilities across major river basins, including the Yangtze and Yellow Rivers.
The role of cationic polyacrylamide in wastewater treatment
The physical, chemical, electrochemical, biochemical, membrane, and other approaches are the primary ways that cationic polyacrylamide is used in the treatment of wastewater from catering. Make use of various methods and kinds of water purifying chemicals.
High oil, high salinity, high chroma, high nutrition, high suspended matter, high COD, odor, and perishable fermentation are the primary features of wastewater from catering. This is due to the fact that various types of leftover food, water, starch, animal fat, vegetable residue, food fiber, and other organic matter make up the majority of catering wastewater. Because these components are combined, treating the water quality of wastewater from catering is challenging and complex.
Factors influencing the effectiveness of PAM
pH
The inorganic flocculant’s use effect is significantly impacted by the water’s pH level. The type of flocculant chosen, the dosage, and the coagulation sedimentation impact all affect the pH value. The flocculant’s hydrolysis reaction involves the participation of the H+ and OH- in the water. Thus, the pH level has a significant impact on the flocculant’s rate of hydrolysis as well as the hydrolysate’s existence and functionality.
The pH value is buffered by the alkalinity of the water. Lime and other agents should be used to augment the alkalinity when it is insufficient. You must add acid to water with a high pH in order to bring it down to neutral. Polymer flocculants, on the other hand, are less sensitive to pH.
Water Temperature
The temperature of the water has an impact on the flocculant’s rate of hydrolysis as well as the structure and rate of alum formation. Coagulation hydrolysis is primarily an endothermic process. The rate of hydrolysis is slow and insufficient at low water temperatures.
Low temperatures cause the water’s viscosity to increase, Brownian motion to weaken, the number of collisions between the flocculant colloidal particles and the water’s impurity particles to decrease, and the water’s shear force to increase. These factors prevent the coagulated flocs from adhering to one another, so even though Even with the flocculant dosage, floc production is still very slow, and the small particles and loose structure make removal challenging.
Polymer flocculants are not significantly affected by low temperatures. However, it should be mentioned that the water temperature shouldn’t be too high while utilizing organic polymer flocculants. The coagulation action will be diminished by high temperatures since they will quickly age or even break down the organic polymer flocculants into insoluble materials.
Impurities
Coagulation benefits from the impurities’ variable particle sizes in the water; small, homogeneous particles will have poor coagulation effects. Coagulation is frequently hampered by impurity particle concentrations that are too low. The coagulation effect can now be enhanced by adding coagulant or refluxing sediment. The coagulation impact will be worse when there is a high concentration of organic matter in the impurity particles in the water. In these cases, the dosage must be increased or oxidants and other coagulation-related agents added. While some anions and surface active chemicals negatively impact coagulation, calcium and magnesium ions, sulfides, and phosphides in water generally aid in coagulation.
Types of flocculants
The choice of flocculant mainly depends on the nature and concentration of colloids and suspended solids in water. If the pollutants in the water are mainly in a colloidal state, inorganic flocculants should be the first choice to make them destabilize and agglomerate. If the flocs are small, it is necessary to add a polymer flocculant or use a coagulant aid such as activated silica gel.
In many cases, the combined use of inorganic flocculants and polymer flocculants can significantly improve the coagulation effect and expand the scope of application. For macromolecules, the greater the amount of charge on the chain molecules, the higher the charge density, the more fully extended the chain, the greater the range of adsorption and bridging, and the better the coagulation effect.
Flocculant Dosage
When coagulation is used to treat any wastewater, there is an optimal flocculant and an optimal dosage, which are usually determined by experiments. Excessive dosage may cause the stability of the colloid. Generally, the dosage range of ordinary iron salt and aluminium salt is 10-100mg/L, the dosage of polymer salt is 1/2～1/3 of the dosage of ordinary salt, and the dosage range of organic polymer flocculant is 1～5mg/L.
Dosing sequence of flocculant
When using multiple flocculants, it is necessary to determine the best dosing order through experiments. Generally speaking, when the inorganic flocculant is used together with the organic flocculant, the inorganic flocculant should be added first, and then the organic flocculant should be added.
When the particle size of the treated impurities is above 50μm, the organic flocculant is often added to absorb the bridge first, and then the inorganic flocculant is added to compress the electric double layer to destabilize the colloid.
Hydraulic Conditions
In the mixing stage, the flocculant and water are required to mix quickly and evenly. In the reaction stage, it is necessary to create enough collision opportunities and good adsorption conditions to allow sufficient growth opportunities for the flocs, and to prevent the small flocs that have been formed from being Broken, so the stirring intensity should be gradually reduced, and the reaction time should be long enough.
Conclusion
Cationic polyacrylamide plays a crucial role in modern wastewater treatment processes. Its ability to effectively flocculate and remove suspended particles, especially in organic-rich waste, makes it an invaluable tool across various industries. By optimizing its application and understanding the factors influencing its performance, we can significantly enhance water quality and promote environmental sustainability. The continued use and research of cationic polyacrylamide will undoubtedly contribute to more efficient wastewater management solutions.
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References
What are cationic polyacrylamide and its applications?
https://polymersco.com/cationic-polyacrylamide/
Flocculants? All you need to know about Polyacrylamide (PAM)
https://www.yasa.ltd/it/post/flocculants-all-you-need-to-know-about-polyacrylamide-pam-1
Function of cationic polyacrylamide in catering wastewater
https://www.hnsecco.com/Function-of-cationic-polyacrylamide-in-catering-wastewater.html
