Neutralizing Acid with Lime Ca(OH)2: Dosage, Cost & Supply
Tóm tắt nội dung
- Why Use Lime to Neutralize Acid in Wastewater
- Mechanism of Acid Reaction with Lime
- How to Calculate Lime Dosage
- Lime Ca(OH)2 vs NaOH — Operating Costs
- Specifications and Supply of Industrial Lime
- Frequently Asked Questions
- Is Lime Powder or Lime Slurry More Effective?
- Does Lime Cause Pipe Blockages?
- How to Ensure Industrial Lime Quality?
- Where to Buy Lime for Industrial Park Wastewater Treatment Plants in the South?
- Can Lime Treat Heavy Metals?
5 Key Points to Remember:
- Lime has lower cost/kg alkali than NaOH — a popular choice for large-scale wastewater treatment plants
- CaSO₄ is sparingly soluble and causes scaling — dosage control and periodic cleaning are necessary when the primary acid source is H2SO4
- Theoretical dosage multiplied by 1.2–1.5 — actual dosage determined by jar testing on real wastewater samples
- 20 tankers of 5–30 tons + 6 warehouses across 3 regions — delivery within 4 hours in Ho Chi Minh City, 24 hours to industrial parks in the South
- COA/MSDS per batch — verify actual Ca(OH)2 content before receiving the goods
Why Use Lime to Neutralize Acid in Wastewater
Wastewater from electroplating, zinc plating, battery production, and metal cleaning often has a pH of 2–5 due to excess H2SO4 or HCl. QCVN 40:2025/BTNMT requires the effluent pH to be 6–9 before discharge. Lime Ca(OH)2 is a popular choice due to its lower cost per kilogram of alkali compared to NaOH, and it provides calcium ions that help precipitate heavy metals and phosphates.
Mechanism of Acid Reaction with Lime
Lime reacts with acid through neutralization equations: H₂SO₄ + Ca(OH)₂ → CaSO₄↓ + 2H₂O and 2HCl + Ca(OH)₂ → CaCl₂ + 2H₂O. Each mole of Ca(OH)₂ (74.1 g) neutralizes 2 moles of H⁺. An important difference: CaSO₄ is sparingly soluble, forming gypsum precipitate that can scale pipes and tanks, while CaCl₂ is fully soluble — this should be considered when the primary acid source is H2SO4.
How to Calculate Lime Dosage
The theoretical lime dosage is calculated based on the excess acid concentration in the wastewater, converted to the moles of H⁺ that need to be neutralized. For example, 1 m³ of wastewater with pH 2 contains approximately 0.01 mol H⁺/L, equivalent to 10 mol H⁺/m³, requiring 5 mol Ca(OH)₂ ≈ 370 g of pure lime. In practice, multiply by a factor of 1.2 to 1.5 due to impurities and buffering — the exact result is determined by jar testing on real wastewater samples. The actual Ca(OH)2 content in industrial lime is clearly stated on the COA for each batch.
Lime Ca(OH)2 vs NaOH — Operating Costs
| Criteria | Lime Ca(OH)2 | NaOH 32% |
|---|---|---|
| Form Supplied | Powder or lime slurry | Solution |
| Cost/kg Alkali | Low | 2–4 times higher |
| Reaction Rate | Slow, requires mixing | Fast, instantaneous |
| By-products | CaSO₄ precipitate (scaling) | Sodium salts fully soluble |
| Sludge Volume | Higher | Lower |
Lime is suitable for large flow rates, limited chemical budgets, and systems with sludge settling tanks. NaOH is suitable when fast reaction, precise pH control via dosing pumps, and minimizing pipe scaling are required.
Specifications and Supply of Industrial Lime
Industrial lime is supplied in 25 kg powder bags or pre-mixed lime slurry for large wastewater treatment plants. Supplier selection criteria: COA per batch stating actual Ca(OH)2 content, uniform particle size, and reliable delivery capacity. Loc Thien supplies lime for industrial park wastewater treatment plants from 6 warehouses across 3 regions, delivered via 20 tankers of 5–30 tons, with COA/MSDS per batch.
Frequently Asked Questions
Is Lime Powder or Lime Slurry More Effective?
Lime slurry reacts faster as it is evenly dispersed, reducing mixing time. Lime powder is cheaper and easier to transport but requires a separate slurry mixing tank and labor for dissolution. Wastewater treatment plants handling over 500 m³/day typically choose pre-mixed lime slurry.
Does Lime Cause Pipe Blockages?
It can, if the primary acid source is H2SO4 — CaSO₄ formed is sparingly soluble, scaling pipes and tanks. Solutions: dose lime in areas with strong mixing, control pH not exceeding 9 (avoid overdosing), and periodically clean pipes with dilute acid.
How to Ensure Industrial Lime Quality?
Three COA indicators: Ca(OH)2 content (minimum 85–90% for industrial lime), particle size, and moisture. Lime is highly hygroscopic — open packaging causes clumping and reduces activity, so inspect goods upon receipt.
Where to Buy Lime for Industrial Park Wastewater Treatment Plants in the South?
Choose a supplier with warehouses near your plant to shorten delivery time and reduce transportation costs. Loc Thien has 6 warehouses across 3 regions (Ho Chi Minh City, Dong Nai, Bac Ninh, Da Nang, Can Tho, BR-VT) — delivery within 4 hours in Ho Chi Minh City, 24 hours to industrial parks in the South.
Can Lime Treat Heavy Metals?
Yes — calcium ions and the alkaline environment from lime help precipitate heavy metals as hydroxides (Cr(OH)₃, Ni(OH)₂, Zn(OH)₂) and phosphates as Ca₃(PO₄)₂. This is why lime both neutralizes acid and removes heavy metals in one step.
Request a Quote for Industrial Lime
Your business is evaluating lime sources for wastewater treatment plants — verify Loc Thien’s capabilities:
- Call 0979 891 929 — consult on lime dosage for your wastewater treatment system, receive a quote within 15 minutes
- Send wastewater samples for Loc Thien technicians to assist with jar testing to determine actual dosage
- Download lime vs NaOH comparison table (PDF) — based on flow rate and wastewater characteristics
Proven Capabilities — Verifiable:
- 20 tankers of 5–30 tons — directly owned, not outsourced. Vehicle registration numbers provided during audits
- 6 warehouses across 3 regions: Ho Chi Minh City, Dong Nai, Bac Ninh, Da Nang, Can Tho, BR-VT — specific addresses for each warehouse
- COA/MSDS per delivery batch — 100% of shipments come with documentation, compliant with ISO 9001/14001
- Direct imports — customs documents ready for NDA signing
LOC THIEN INVESTMENT DEVELOPMENT CO., LTD — Tax Code: 0313650856 · Hotline: 0979 891 929 · hoachatlocthien.com