PAC Technology: Comparison, Classification of PAC Powder & Production Process
5 key points to remember:
- Basicity is the most important technical parameter — determines the percentage of aluminum in active polymer form
- PAC powder (28-30%) saves 60-70% transportation costs compared to liquid PAC with the same active content
- PAC is produced from Al(OH)₃ + HCl at 120-180°C, pressure 0.2-0.5 MPa
- Quality standard: GB 15892-2020 (China) — request COA when purchasing
- Loc Thien Chemicals provides standard-compliant PAC, COA/MSDS per batch — call 0979 891 929
1. Basicity — The Key Technical Parameter Determining PAC Quality
1.1. What is Basicity?
The basicity of PAC, denoted as B (%), is defined as the molar ratio between hydroxyl groups [OH⁻] and aluminum [Al³⁺] in the molecule:
B (%) = ([OH⁻] / 3[Al³⁺]) × 100
In other words, basicity reflects the degree of polymerization of PAC — the percentage of Cl⁻ positions in AlCl₃ that have been replaced by OH⁻ groups to form polymer chains [Al₂(OH)ₙCl₆₋ₙ]ₘ.
1.2. Effect of Basicity on Coagulation Efficiency
| Basicity | Characteristics | Suitable Applications |
|---|---|---|
| 40–55% (Low) | High free Al³⁺ content, low polymerization. Slower coagulation, requires alkaline pH. | Mildly acidic wastewater, low turbidity water |
| 55–70% (Medium) | Balance between monomer and polymer. Good efficiency across a wide pH range. | Conventional water treatment |
| 70–85% (High) | High polymerization, fast coagulation, large flocs, rapid settling. Widest pH range. | High turbidity source water, industrial wastewater |
| >85% (Very High) | Very long polymers, easy floc formation but difficult to store (prone to gelation). Shorter shelf life. | Special applications, requires strict control |
Practical Note: PAC 31% in the Vietnamese market typically has a basicity of 60–80%. PAC with higher basicity tends to have a darker color (dark yellow to brown) — this is a natural characteristic of the product, not a sign of poor quality.
2. Comparison of PAC Powder and PAC Liquid — Which Form to Choose?
2.1. Comprehensive Comparison Table
| Criteria | PAC Powder 28–30% | PAC Liquid 10–31% |
|---|---|---|
| Actual Al₂O₃ | 28–30% | 3–10% (depending on type) |
| Transportation Cost/kg Al₂O₃ | VERY LOW — mainly transporting active content | HIGH — transporting 70–90% water |
| Storage | 25kg bags on pallets, dry warehouse | FRP/HDPE tanks, large area |
| Operation | Requires preparation (powder → 5–10% solution) | Direct pumping from tank/drum |
| Labor | Requires 1–2 workers for preparation | Fully automated with dosing pumps |
| Dust/Safety | PAC dust causes respiratory irritation — PPE required | Dust-free, safer operation |
| Shelf Life | 12 months (sealed, dry) | 6 months (liquid PAC degrades faster) |
| Suitable Users | Plants far from supply, export, no large storage tanks | Plants near warehouses, stable capacity, have storage tanks |
2.2. When to Choose PAC Powder?
Choose PAC powder when:
- Your plant is far from the supply source (Central, Central Highlands, Northern mountainous regions) — transportation cost for liquid PAC (containing 70–90% water) will be very high
- You need to export — PAC powder in 25kg bags is easy to transport in containers
- Your plant has an existing preparation system (mixing tank, solution storage tank)
- Consumption is seasonally unstable — powder has a longer shelf life, no risk of spoilage
2.3. When to Choose PAC Liquid?
Choose PAC liquid when:
- Your plant is near large industrial parks (Binh Duong, Dong Nai, Ho Chi Minh City, Long An, Hanoi) — Loc Thien delivers directly
- Capacity is stable, high consumption (>5 tons/month)
- You want full automation — liquid PAC is pumped directly, no preparation needed
- No investment in preparation and dust handling systems
3. PAC Production Process
3.1. Production Principle
PAC is produced by the reaction between aluminum hydroxide Al(OH)₃ and hydrochloric acid HCl under controlled temperature and pressure:
x Al(OH)₃ + y HCl + z H₂O → [Al₂(OH)ₙCl₆₋ₙ·xH₂O]ₘ (PAC)The reaction is carried out in a pressure reactor (autoclave reactor) at 120–180°C and pressure 0.2–0.5 MPa for 4–8 hours. The molar ratio of Al(OH)₃:HCl and reaction conditions determine the basicity of the final product.
3.2. Main Production Steps
- Feeding: Al(OH)₃ (white powder, purity ≥99%) + HCl (31–33%) + water are fed into the reactor in calculated ratios
- Reaction: Heating to 120–180°C, maintaining pressure at 0.2–0.5 MPa, continuous stirring for 4–8 hours. During this stage, Al(OH)₃ gradually dissolves in HCl, hydrolysis and polymerization occur simultaneously
- Cooling: Reducing temperature to <80°C
- Filtration: Removing insoluble residues (excess Al(OH)₃, impurities) through a filter
- Adjustment: Adjusting Al₂O₃ concentration to target levels (10%, 5%, 3%) by adding water or concentrating
- Quality Check: Sampling to test Al₂O₃, basicity, pH, metal impurities — issuing COA
- Packaging: Liquid PAC → finished product tank; PAC powder → spray drying → 25kg bags
3.3. PAC Powder Production (Spray Drying)
To produce PAC powder from liquid PAC:
- Liquid PAC is sprayed into mist in a drying tower at 200–300°C
- Water evaporates instantly, PAC precipitates into fine powder particles
- Powder is collected via cyclone, packed immediately while still warm to avoid moisture absorption
- High-quality PAC powder has an ivory to light yellow color, dissolves quickly in water
4. Quality Standards and How to Read COA
4.1. Reference Standards
| Standard | Scope |
|---|---|
| GB 15892-2020 | Chinese standard — most common for PAC imported into Vietnam |
| TCVN | Vietnamese standard — reference, applied for domestically circulated PAC |
| AWWA B408 | American standard — applied for PAC used in drinking water |
| EN 883 | European standard — PAC for drinking water |
4.2. How to Read COA — 5 Most Important Indicators
When receiving COA from suppliers, engineers should focus on 5 indicators:
| Indicator | Meaning | Target Value |
|---|---|---|
| Al₂O₃ (%) | Active content | As labeled (±0.5%) |
| Basicity (%) | Degree of polymerization | 40–90%, higher is better for fast coagulation |
| Water Insolubles (%) | Inert residues, inactive | <0.5% (powder), <0.2% (liquid) |
| Fe (mg/kg) | Iron impurities — causes yellowing of treated water | <500 mg/kg (drinking water), <2,000 mg/kg (wastewater) |
| Heavy Metals (As, Pb, Hg, Cd, Cr⁶⁺) | Toxicity | Meets TCVN for drinking water (for PAC used in drinking water) |
5. Loc Thien — Source of Standard-Compliant PAC
Loc Thien Chemicals provides PAC from ISO 9001, ISO 14001 certified factories, with full COA for each batch:
- Transparent Origin: PAC imported officially from China and India — full COA, MSDS, C/O (Certificate of Origin)
- 6 Warehouses Nationwide — quality control at input and proper storage
- 20 Dedicated Tank Trucks — no cross-contamination, no degradation during transportation
- Technical Support: Loc Thien engineers advise on selecting PAC suitable for water source parameters and plant treatment processes
Call 0979 891 929 — quote within 15 minutes, with COA for current batch.
6. Frequently Asked Questions
What is the Best Basicity for PAC?
There is no absolute “best” number. PAC with basicity 70–85% offers the highest coagulation efficiency for most water sources. However, PAC with basicity >85% is harder to store (prone to gelation). For mildly acidic wastewater, PAC with basicity 50–65% may be more suitable.
Why Does Liquid PAC with the Same Al₂O₃ Content Have Different Prices Among Suppliers?
Because of differences in basicity and impurities. PAC with high basicity (70–85%) has higher production costs than PAC with low basicity (40–55%). Additionally, PAC meeting drinking water standards (very low heavy metal content) is more expensive than technical PAC for wastewater.
Does Self-Prepared PAC Powder Reduce Quality?
If prepared correctly (powder → water, stirring for 30-60 minutes) and used within 24-48 hours, quality is not compromised. However, self-prepared PAC powder may have insoluble residues if the mixing water has high hardness (Ca²⁺, Mg²⁺ precipitates with PAC) — use clean water, tap water for preparation.
Can PAC Be Combined with FeCl₃?
Yes. Combining PAC + FeCl₃ (ratio 2:1 or 3:1) often yields higher coagulation efficiency in treating wastewater with stubborn color (dyeing wastewater, leachate). Jar test is needed to determine the optimal ratio.
How to Detect Poor Quality PAC Upon Receipt?
3 quick checks: (1) Measure density — PAC 31% must reach 1.19-1.21 g/cm³, lower means diluted, (2) Prepare 1% solution and measure pH — must be within 3.5-5.0, (3) Run jar test comparing with previously used PAC sample — if dosage is 1.5 times higher but efficiency is still poor → suspect quality.
LOC THIEN INVESTMENT DEVELOPMENT COMPANY LIMITED
Tax Code: 0313650856 — Address: 219/19A, Binh Phuoc B Hamlet, Binh Chuan Ward, Thuan An City, Binh Duong Province
Hotline: 0979 891 929 — Email: [email protected]
Website: hoachatlocthien.com