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20
2025
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03
Comparative analysis of polyacrylamide with other flocculants (such as PAC, aluminum sulfate)
In the fields of wastewater treatment, sludge dewatering, and industrial solid-liquid separation, the choice of flocculant directly affects treatment efficiency and cost. Polyacrylamide (PAM), polyaluminum chloride (PAC), and aluminum sulfate, as three mainstream flocculants, have different application scenarios due to their differences in chemical properties and mechanisms of action. This article objectively compares them in terms of technical performance, economy, and environmental protection, providing a reference for industry selection.
I. Differences in mechanism of action and chemical characteristics
Polyacrylamide (PAM)
Type: Organic polymer flocculant, divided into anionic, cationic, and non-ionic types.
Mechanism: Through the "adsorption bridging" action of the long-chain molecular structure, it quickly aggregates suspended particles to form large flocs, suitable for high-turbidity wastewater or systems containing fine particles.
Characteristics: High molecular weight (usually over 10 million), low dosage (0.1~10 ppm), but the dissolution concentration and stirring speed must be strictly controlled.
Polyaluminum chloride (PAC)
Type: Inorganic polymer coagulant, existing in the form of hydroxyl complexes.
Mechanism: By compressing the colloidal double electric layer through the electric neutralization effect, it promotes particle destabilization and coagulation, suitable for medium and low turbidity water bodies (such as drinking water pretreatment).
Characteristics: Wide applicable pH range (5~9), dense flocs, but high dosage (10~100 ppm).
Aluminum sulfate
Type: Traditional inorganic salt coagulant.
Mechanism: Hydrolysis generates aluminum hydroxide colloid to adsorb impurities, and needs to be effective in a weakly acidic environment (pH 6~7).
Characteristics: Low cost, but high dosage (50~200 ppm), high sludge production, and easy to cause pH fluctuations in water.
II. Comparison of core performance and economy
III. Typical application scenarios and selection suggestions
Scenarios where PAM is preferred
Industrial wastewater: Systems with high suspended solids such as oily wastewater and papermaking black liquor;
Sludge dewatering: Used with filter presses to improve dewatering efficiency;
Special needs: Projects requiring rapid sedimentation or reduced sludge volume.
Applicable fields of PAC
Municipal wastewater: Primary treatment of domestic sewage;
Drinking water purification: Low toxicity characteristics meet water quality safety requirements;
Sudden pollution: Rapid addition in emergency treatment.
Economical solution of aluminum sulfate
Small wastewater treatment plants: Scenarios with limited budget and small water quality fluctuations;
Pretreatment of acidic wastewater: Adjust pH while achieving preliminary coagulation.
IV. Environmental protection and future trends
Environmental risks
Excessive addition of PAM should be avoided to prevent residual monomer pollution;
The problem of aluminum salt residue in PAC promotes the research and development of low-aluminum products;
Acidic by-products of aluminum sulfate need to be neutralized.
Technical trends
Compound flocculants: PAM and PAC are combined to enhance synergistic effects;
Green modification: Developing biodegradable PAM and efficient and low-consumption preparation processes;
Precise dosing: Intelligent dosing system based on online water quality monitoring.
Conclusion
Polyacrylamide, PAC, and aluminum sulfate form a complementary pattern in the field of flocculation. Selection should comprehensively consider water quality characteristics, treatment goals, and the whole life cycle cost, avoiding blindly pursuing low price or single performance indicators. With the increasingly stringent environmental regulations and technological progress, efficient, low-consumption, and environmentally friendly flocculation technology will become the core direction of industry upgrading.
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