The most common question we get from new customers: "Should I use anionic or cationic PAM?" The answer depends on your water chemistry, not on price or availability. Using the wrong type will give you poor flocculation no matter how much you dose. Here is the decision framework we use with customers across 45+ countries.
Side-by-Side Comparison
| Property | Anionic PAM (APAM) | Cationic PAM (CPAM) |
|---|---|---|
| Charge | Negative (anionic) | Positive (cationic) |
| Charge density range | 0–45% hydrolysis | 5–70% charge density |
| Molecular weight range | 6–28 million Da | 6–20 million Da |
| Best for | Inorganic solids, mining, drinking water | Organic sludge, municipal wastewater |
| Optimal pH range | 6–12 (neutral to alkaline) | 4–9 (acidic to neutral) |
| Typical dosage | 1–10 ppm | 3–8 kg/ton dry solids |
| Price (approx.) | $1,600–2,200/ton | $1,800–2,500/ton |
The Core Rule: Match Charge to Particle
Flocculation works by charge neutralization and polymer bridging. The polymer charge must attract the particle charge — opposites attract.
Most suspended particles in water carry a negative surface charge: clay minerals, silica, metal hydroxides, and most inorganic solids. These respond to cationic PAM (positive charge attracts negative particles).
For projects like this, our high charge density CPAM delivers consistent results with factory-direct pricing.
Wait — that seems backwards from the table above. Here is the nuance: for sludge dewatering, you are treating organic sludge (negatively charged bacteria and organic matter) with CPAM. For clarification of inorganic-heavy water, APAM works through bridging rather than charge neutralization, and it is often used after an inorganic coagulant (alum, ferric) that has already neutralized the charge.
When to Use Anionic PAM
APAM is the right choice in these situations:
- Mining and mineral processing — tailings clarification, thickener feed, water recovery. The high molecular weight (15-28M Da) creates large, fast-settling flocs from fine mineral particles.
- Drinking water treatment — used as a coagulant aid after alum or ferric dosing. Must be NSF/ANSI 60 certified with residual monomer ≤0.05%.
- Industrial wastewater with inorganic solids — electroplating, metal finishing, sand washing, stone cutting.
- Oil drilling — PHPA (partially hydrolyzed PAM) stabilizes wellbore and reduces fluid loss.
- Sugar industry — juice clarification in sugar mills.
Our APAM range: 6-28 million molecular weight, 0-45% hydrolysis degree. For mining applications, we typically recommend 18-25M MW with 25-35% hydrolysis. For drinking water, 10-15M MW with 10-20% hydrolysis.
When to Use Cationic PAM
CPAM is the right choice when you are dealing with organic-rich water or need to dewater sludge:
- Municipal sludge dewatering — belt press, centrifuge, filter press. This is the largest application for CPAM globally.
- Industrial organic wastewater — food processing, slaughterhouses, breweries, paper mills.
- Paper making — retention aid and drainage aid on the paper machine.
- Oilfield produced water — treating water separated from crude oil.
- Textile wastewater — when pH is in the 5-8 range.
Our CPAM range: 6-20 million molecular weight, 5-70% charge density. The charge density selection matters more than molecular weight for most sludge applications. Start with 30-40% charge density and adjust based on jar test results.
See our detailed guide on cationic PAM selection and bulk pricing.
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Decision Flowchart
Follow these questions in order:
- Is the pH below 4? → Use nonionic PAM (NPAM). Both APAM and CPAM lose effectiveness in strongly acidic conditions.
- Are you dewatering sludge? → Use CPAM. Sludge is organic and negatively charged.
- Is the wastewater primarily organic? (food, paper, municipal) → Use CPAM.
- Is it primarily inorganic? (mining, metal processing, sand) → Use APAM.
- Is it for drinking water? → Use APAM with NSF certification.
- Still unsure? → Run a jar test with both types at 2-5 ppm and compare settling rate and supernatant clarity.
Can You Mix APAM and CPAM?
No. Mixing anionic and cationic PAM causes immediate precipitation — the opposite charges react and form an insoluble complex. Always dose them separately, and never mix them in the same preparation tank. For proper dissolution techniques, see our PAM dissolving method guide.
In some two-stage treatment systems, APAM is used in the first stage (clarification) and CPAM in the second stage (sludge dewatering). This is fine as long as they are dosed at different points in the process. Learn more about dosage calculation and molecular weight selection.
Our Product Range
At our Zhengzhou factory, we produce both APAM and CPAM on dedicated production lines with 100,000 tons/year total capacity. Every batch goes through 3-tier quality control: in-process monitoring, full batch testing, and pre-shipment inspection.
Key specs we guarantee: solid content ≥92%, dissolution time ≤90 minutes, residual monomer ≤0.05%. We hold ISO 9001, ISO 14001, ISO 45001, and NSF certifications.
MOQ is 500kg for first orders — enough to run thorough jar tests and pilot trials before committing to bulk supply. Standard delivery is 7-10 days; urgent orders ship in 3-5 days from stock.
Not Sure Which to Choose?
Send us your wastewater analysis (pH, TSS, COD, conductivity) and we will recommend the right type and grade within 24 hours. We also offer free samples for testing.
WhatsApp: +86 150-0381-8598 | Request a quote
Get a Quote
Our factory in Zhengzhou produces 100,000 tons/year of PAM across 18+ grades. MOQ 500kg, delivery 7-10 days standard. Contact us for pricing and free sample:
- WhatsApp: +86 150-0381-8598
- Email: info@chinapolyacrylamide.com