PolyDADMAC (polydimethyldiallylammonium chloride)is a cationic organic high-molecular flocculant, widely used in wastewater treatment. It mainly removes suspended solids, colloids and organic pollutants in water through charge neutralization and adsorption bridging. The following are its specific applications and mechanisms of action in wastewater treatment:
1. Principle of action
Charge neutralization: PolyDADMAC carries a high density of positive charge (strong cationic property), which can neutralize negatively charged colloidal particles (such as bacteria, humic acid, clay, etc.) electrically, destroying the stability of the colloid and causing it to destabilize and aggregate.
Adsorption bridging: Its long-chain polymer structure can adsorb multiple particles, forming a “bridging” effect, promoting the aggregation of tiny flocs into large particles, which is convenient for subsequent sedimentation or filtration.
2. Application scenarios
Municipal and industrial wastewater treatment
Primary flocculation: As a pretreatment agent, it can quickly remove suspended solids (SS) and colloidal substances in wastewater and reduce turbidity.
Enhanced coagulation: When used in combination with inorganic coagulants (such as PAC and aluminium sulfate), it enhances the flocculation efficiency and reduces the dosage of inorganic chemicals.
Sludge dewatering: As a conditioner, it improves the settling property and dewatering performance of sludge and reduces the volume of sludge
Specific wastewater treatment
Oily wastewater: Neutralize the surface charge of oil droplets and promote the separation of oil and water.
Printing and dyeing wastewater: Remove negatively charged dye molecules (such as reactive dyes and acid dyes).
Papermaking wastewater: Capture anionic impurities (such as lignin, fine fibers) to reduce COD and color.
3. Key Points for Use
Dosage optimization: The optimal dosage needs to be determined through experiments (such as beaker tests). Excessive dosage may cause charge inversion (re-stabilization of the colloid).
pH adaptability: It is effective within a wide pH range (3-10), but under acidic conditions, the positive charge density is higher and the effect is better.
Compatibility: It can be used in stages with anionic flocculants (such as PAM), but direct mixing should be avoided to prevent sedimentation.
4. Advantages and Limitations
Advantages:
The reaction speed is fast and the flocs are dense.
There is no residue of metal ions, making it suitable for processes sensitive to metals.
Resistant to chlorine oxidation and highly stable.
Limitations:
The removal effect on dissolved organic matter (such as small molecule organic matter) is limited;
The cost is higher than that of inorganic coagulants.
5. Environment and Safety
Biodegradability: It is difficult to biodegrade, but the residue is low and usually meets the discharge standards.
Toxicity: Low toxicity, but the dosage needs to be controlled to avoid potential inhibition on microorganisms (such as biochemical treatment units).
PolyDADMAC is used as an efficient flocculant in wastewater treatment, especially suitable for wastewater with high turbidity and high colloidal content. Its core value lies in the rapid realization of solid-liquid separation, and it is often used in combination with other water treatment technologies (such as activated sludge process and membrane filtration) to optimize the overall treatment effect. In practical applications, parameter adjustments need to be made in combination with the characteristics of water quality.
