Introduction
Buying PAC and PAM is straightforward — buying the RIGHT PAC and PAM for your specific application is not. Many procurement decisions are made on price per ton alone, ignoring specifications that directly determine the total cost per cubic meter treated. This guide provides a systematic checklist of 10 specifications to evaluate when purchasing water treatment chemicals, helping you avoid costly mistakes and supplier quality issues.
1. Al2O3 Content (PAC) — But It’s Not Everything
What it means: Aluminum oxide content as a percentage by weight. Industry standard: 28% or 30%.
Why it matters: Higher Al2O3 = more active coagulant per kg. A 28% PAC requires 7% more product than a 30% PAC for the same dose.
How to verify: Request COA with Al2O3 by titration method (not calculated from Al content). Beware of suppliers inflating Al2O3 — claim 30% but deliver 26-28%. Independent lab verification recommended for initial shipments.
Common mistake: Buying purely on Al2O3%. A 30% Al2O3 PAC with 40% basicity may perform WORSE than a 28% Al2O3 with 70% basicity for your application. Al2O3 is quantity of aluminum; basicity determines the effectiveness of that aluminum.
2. Basicity (%OH) — The Hidden Performance Factor
What it means: Degree of pre-hydrolysis (see our PAC Basicity Guide for full details).
Why it matters: Determines coagulation mechanism (charge neutralization vs bridging), pH range, and dosage requirement.
How to verify: COA should state basicity by standard titration method. Typical commercial ranges: 40-85%.
Specification tip: Specify a range, not a minimum. “Basicity 65-80%” is better than “Basicity >65%” — too-high basicity can cause re-stabilization in low-turbidity applications.
3. Heavy Metal Content — Especially for Drinking Water Applications
Critical metals: Arsenic (As), Lead (Pb), Cadmium (Cd), Chromium (Cr), Mercury (Hg).
Limits: Vary by application. Drinking water grade: As <2 mg/kg, Pb <10 mg/kg. Industrial grade: typically 2-5x higher limits.
How to verify: Request heavy metal analysis by ICP-MS or AAS from an accredited lab. Supplier in-house testing is acceptable if the lab is ISO 17025 accredited. For drinking water, request NSF/ANSI 60 certification or equivalent national standard compliance letter.
Red flag: Supplier cannot provide heavy metal test data. Every legitimate PAC manufacturer has this data — not having it means either not testing (negligent) or hiding results (worse).
4. Water Insolubles — The Invisible Wasted Chemical
What it means: Percentage of PAC that does not dissolve in water. Consists of unreacted raw material, clay/silica impurities, and manufacturing residues.
Why it matters: Insoluble PAC doesn’t coagulate — it just adds to sludge. 1% insolubles in 100 tons/year = 1 ton of inert waste you paid coagulant prices for, plus sludge disposal cost.
Specification target: Spray dried PAC: <0.2%. Drum dried PAC: <1.0%. Drinking water grade: <0.1%.
How to verify: Simple field test: Dissolve 10g PAC in 1000mL distilled water, stir 15 min, filter through pre-weighed filter paper, dry and weigh residue. Insolubles % = (residue weight / 10g) x 100.
5. Dissolution Rate — Matters for Automated Plants
What it means: Time for PAC powder to fully dissolve in water at a specified temperature and mixing speed.
Why it matters: Slow-dissolving PAC in an automatic dosing system = undissolved powder reaching the dosing point = wild swings in effective dose. Spray dried PAC: 3-8 minutes. Drum dried PAC: 15-45 minutes.
How to verify: Conduct dissolution test at your plant’s water temperature and mixing conditions. Record time to visually clear solution (no visible particles).
6. Molecular Weight (PAM) — The Floc Size Determinant
What it means: Average molecular weight of PAM polymer chains, measured in millions of Daltons (e.g., 15 million MW).
Why it matters: Higher MW = longer polymer chains = larger flocs = faster settling. But too high MW = fragile flocs that break under shear; too low MW = fine flocs that settle slowly.
Selection guide:
- Mining tailings, coarse particles: 12-18 million MW
- Fine clay, general wastewater: 18-22 million MW
- Ultra-fine particles (phosphate clay): 22-25 million MW
- Sludge dewatering (cationic): 5-12 million MW
How to verify: Intrinsic viscosity measurement by Ubbelohde viscometer, converted to MW using Mark-Houwink equation. Supplier COA should state MW. Field proxy: Solution viscosity at 0.1% concentration — higher MW PAM gives noticeably more viscous solution.
7. Ionic Charge and Charge Density (PAM)
What it means: For anionic PAM: degree of hydrolysis (% carboxyl groups). For cationic PAM: degree of cationization (% quaternary ammonium groups).
Why it matters: Charge density determines how the polymer interacts with particle surfaces and dissolved ions in the water. High-charge PAM is more sensitive to hardness (Ca2+, Mg2+) — the charge gets neutralized by hardness ions, collapsing the polymer chain.
Selection guide:
- Low charge (5-15%): High-hardness water (>500 mg/L CaCO3), high-TDS applications
- Medium charge (15-30%): General purpose, moderate hardness
- High charge (30-50%): Low-hardness, low-TDS water. Best flocculation but narrowest operating window
8. Bulk Density and Packaging Integrity
Why it matters: Affects shipping cost (lower density = more bags per ton of active = higher freight per active kg), storage volume, and moisture absorption during storage.
What to check:
- Bulk density: Spray dried PAC 0.55-0.70 g/cm3, drum dried 0.65-0.85 g/cm3. Significant deviation from these ranges may indicate product change or quality issue
- Bag integrity: PE inner liner must be intact. Torn liner = PAC absorbs moisture = clumps and loses dissolution speed
- Moisture content: <3% for powder PAC. High moisture = caking and reduced active content per kg
9. Batch-to-Batch Consistency
Why it matters: If each container of PAC has different basicity or Al2O3, the plant must constantly adjust dosing — leading to treatment upsets. This is a major quality indicator separating professional manufacturers from traders who blend from multiple sources.
How to check:
- Request COAs for the last 5 production batches. Look at the range (max – min) for key parameters. Al2O3 range should be <1.0%; basicity range <5%
- Blend a sample from each bag in the first container (composite 20 bags) and test Al2O3 and basicity. Compare with the supplier’s COA
- Repeat on the next container. Compare results. Large variation = the supplier is blending from multiple sources
10. Supplier Reliability — Beyond the COA
Check before you commit to a bulk purchase:
- Factory visit or third-party audit: Verify production equipment (stainless steel for drinking water grade, spray tower for spray dried claims), raw material storage, and QC lab
- Production capacity vs your demand: A supplier producing 5,000 tons/year cannot reliably supply your 2,000 tons/year order — they’ll blend or trade to fill the gap
- Export experience: Documentation (COA, MSDS, certificate of origin, SONCAP, SASO, etc.) should be standard, not something they “can arrange.” Export-experienced suppliers provide these without being asked
- Sample consistency with bulk shipment: Request a production sample (from an actual production batch, not a “special sample”). Compare with the pre-shipment sample from your first bulk order. They should match
- Communication responsiveness: How long do they take to respond to technical questions? 24-48 hours is normal. Weeks of delay = they won’t support you if a quality problem arises
Checklist Summary
| # | Specification | PAC Target | PAM Target | Verification Method |
|---|---|---|---|---|
| 1 | Active content | Al2O3 28-30% | Solid content >88% | Titration / COA |
| 2 | Basicity (PAC only) | 40-85% (application-specific) | — | Titration / COA |
| 3 | Heavy metals | As <2, Pb <10, Cd <2, Cr <5 mg/kg (drinking water) | Not typically specified | ICP-MS by accredited lab |
| 4 | Water insolubles | <0.2% (spray dried) | <1.0% | Filtration + gravimetric |
| 5 | Dissolution rate | <10 min (spray dried) | 60-90 min (complete) | Visual + turbidity |
| 6 | MW (PAM only) | — | 8-25 million (application-specific) | Intrinsic viscosity |
| 7 | Charge density (PAM) | — | 5-50% (application-specific) | Colloid titration / COA |
| 8 | Bulk density | 0.55-0.85 g/cm3 | 0.6-0.8 g/cm3 | Weigh fixed volume |
| 9 | Batch consistency | Al2O3 range <1%, basicity range <5% | Viscosity range <10% | Compare 5 batch COAs |
| 10 | Supplier reliability | Audit, references, export documentation capability, sample consistency | Factory audit, references | |
HydroChemix provides complete COA documentation, batch-to-batch consistency data, and pre-shipment samples for all orders. Contact jingshuicc@gmail.com for product specifications, sample COAs, and to discuss your procurement requirements.