Flocculant Selection Chart: PAM vs PolyDADMAC vs Polyamine by Charge and Application

Organic flocculants build coagulated particles into flocs that settle, float or dewater. Choosing the right one is mostly about charge and molecular weight – after coagulation has done its job. This page pulls the three main organic flocculants (polyacrylamide, PolyDADMAC and polyamine) into one chart, with the charge logic that decides the choice.

1. The sequence: coagulant first, flocculant second

Coagulants (PAC, alum, ferric) destabilise particles and neutralise charge. Flocculants then bridge those particles into large, fast-settling flocs. Using a flocculant without proper coagulation gives poor, expensive results – the two work as a pair.

2. Two questions decide the flocculant

Charge. Opposites attract: a cationic flocculant acts on negatively charged particles (most organic sludge, many waters); an anionic flocculant acts on positively charged particles (metal hydroxides, mineral tailings).
Molecular weight and charge density. High molecular weight bridges flocs for settling/dewatering; high charge density neutralises and coagulates. Match to the job.

3. Side-by-side comparison

Factor	PAM (polyacrylamide)	PolyDADMAC	Polyamine
CAS	9003-05-8 (typical)	26062-79-3	42751-79-1
Charge type	Anionic, cationic or nonionic	Cationic (high charge)	Cationic
Molecular weight	Low to very high (by grade)	Low to medium	Low to medium
Charge vs pH	Depends on grade	Essentially pH-independent	pH-dependent
Main role	Bridging flocs; clarification and dewatering	Charge neutralisation + coagulation	Charge neutralisation + coagulation
Best for	Sludge dewatering, tailings, clarification, agriculture	Drinking water, papermaking, industrial clarification	Wastewater, sludge dewatering, oil-water separation

4. PAM: pick the charge first

PAM type	Charge	Typical use
Anionic	Negative	Mineral tailings, metal hydroxide sludge, high-turbidity inorganic solids; often high molecular weight
Cationic	Positive	Organic sludge dewatering (municipal/industrial), papermaking, water with negative colloids
Nonionic	Neutral	Specific slurries where charge is not the driver; some mineral and industrial uses

See anionic vs cationic vs nonionic PAM for the full grade logic.

5. Selection chart by application

Application	First choice	Notes
Drinking water clarification	PolyDADMAC (or a cationic coagulant)	High charge, pH-independent; check the drinking-water approvals (NSF standards)
Municipal / industrial sludge dewatering	Cationic PAM	High molecular weight for strong, dry cake
Mineral tailings thickening	Anionic PAM (high MW)	See PAM in mining
Paper and board (retention / drainage)	PolyDADMAC or polyamine	Charge-driven; works with the wet-end chemistry (PolyDADMAC in papermaking)
Oil-water separation / produced water	Polyamine or cationic PAM	Charge neutralisation of oily emulsions (polyamine for oil-water separation)
High-colour / high-NOM water	Cationic polymer with a coagulant	Pair with PAC or ferric for best results
Agriculture / erosion control	Anionic PAM	Soil conditioning (PAM in agriculture)

6. Quick decision rules

Organic sludge / negative colloids? Cationic polymer (cationic PAM, polyamine or PolyDADMAC).
Mineral / inorganic solids? Anionic PAM (high molecular weight).
Need charge neutralisation more than bridging? High-charge polymer (PolyDADMAC, polyamine).
Need fast settling / dry cake? High-molecular-weight PAM.
Drinking water? PolyDADMAC with the right approvals; avoid unapproved grades.
pH varies? PolyDADMAC’s charge is pH-independent; polyamine’s is not.
Always jar-test or plant-trial the grade: two polymers with the same nominal charge can behave very differently.

7. Typical dosage

Use	Typical dose (starting point)
Clarification	About 0.5 – 5 mg/L active polymer
Sludge dewatering	Set by kg polymer per tonne dry solids; test per sludge
Tailings thickening	About 10 – 50 g per tonne of solids

Flocculant dose is always set by test – jar test for clarification, plant trial for dewatering.

8. Make-up and dosing

Dilute first. PAM is made up to about 0.1-0.5% before dosing.
Avoid shear. Over-mixing breaks flocs and wastes polymer.
Dose point. Add after coagulation, with gentle mixing and enough contact time.
Water quality. Use clean, low-hardness water for make-up.

Frequently Asked Questions

What is the difference between a coagulant and a flocculant?

Coagulants (PAC, alum, ferric) destabilise and neutralise particles; flocculants (PAM, PolyDADMAC, polyamine) bridge them into large flocs that settle or dewater.

Which flocculant for sludge dewatering?

Usually a cationic PAM, selected by charge density and molecular weight in a plant trial on your sludge.

Which flocculant for mineral tailings?

Usually an anionic, high-molecular-weight PAM. See the mining tailings guide.

Can PolyDADMAC be used for drinking water?

Yes, where the grade meets the relevant drinking-water approvals (for example NSF-listed). Check the certification for your market.

Why do two similar PAMs behave differently?

Charge type, charge density, molecular weight and the polymer’s structure all affect performance, so grades that look alike on paper can behave very differently on the same slurry – test them.