FeCl2 and FeCl3 – Iron Chlorides
FeCl2 and FeCl3 – Iron Chloride: An Indispensable Industrial Chemical in Water Treatment & Manufacturing
Quick Summary: FeCl2 (Ferrous Chloride / Iron(II) Chloride) and FeCl3 (Ferric Chloride / Iron(III) Chloride) are two important industrial chemicals. FeCl2 is used in the Fenton reaction, for Cr(VI) reduction, and in Wastewater Treatment. FeCl3 is used for PCB etching and water coagulation. Both are supplied by Loc Thien Chemicals in Ho Chi Minh City.
What are FeCl2 and FeCl3? A Quick Overview
FeCl2 (Ferrous Chloride) and Ferric Chloride Used in textile fiber preparation and related alkaline process steps prior to dyeing.
These two chemicals are often confused due to their similar names, but they have completely different properties and uses. This article explains each type in detail, compares their differences, and provides guidance on selecting the correct type based on actual needs.
Part 1: FeCl₂ – Ferrous Chloride
1.1 Basic Information
| Specifications | Value |
|---|---|
| Chemical Name | Ferrous chloride |
| Formula | Iron(II) chloride |
| CAS Number | 7758-94-3 |
| Molar mass | 126.75 g/mol |
| Commercial content / Purity | 15–30% (solution) |
| Common sources | Vietnam |
| Packaging | 30 kg can / 200 kg drum / IBC tank / Tank truck |
1.2 Physical Properties
FeCl₂ exists in two main forms:
- Anhydrous form: A white or pale gray solid with a density of 3.16 g/cm³ and a melting point of 677°C.
- Hydrated form FeCl₂·4H₂O: Light green or pale blue crystals, density 1.93 g/cm³, melting point 105°C.
- Highly soluble in water: 64.4 g/100 mL (10°C) → 105.7 g/100 mL (100°C).
- Upon exposure to air, it is easily oxidized to FeCl₃.
1.3 Chemical Properties
FeCl₂ exhibits all the properties of a salt, particularly strong reducing properties:
Reaction with bases:
FeCl₂ + 2NaOH → Fe(OH)₂↓ + 2NaClReaction with salts:
FeCl₂ + 2AgNO₃ → Fe(NO₃)₂ + 2AgCl↓It is oxidized by Cl₂ to form FeCl₃:
2FeCl₂ + Cl₂ → 2FeCl₃1.4 Applications of FeCl₂
✅ Industrial wastewater treatment
FeCl₂ is an effective coagulation agent in Wastewater Treatment systems. It reacts with impurities to form precipitated iron hydroxide, which carries contaminants, heavy metals, phosphates, and organic matter to the bottom of the tank.
Specific applications:
- Textile Dyeing Wastewater Treatment (Decolorization)
- Livestock wastewater treatment
- Electroplating wastewater treatment (removal of chromium and nickel)
- Hospital wastewater treatment
- Landfill leachate treatment
✅ Textile Dyeing
FeCl₂ is used as a mordant in the dyeing of natural fabrics, helping colors adhere more firmly and increasing colorfastness during washing and when exposed to light.
✅ Metallurgy and Electroplating
- Rust removal and surface preparation of metals prior to electroplating
- Provides a corrosion-resistant protective layer for steel and alloys
✅ Intermediate Chemicals
FeCl₂ is a raw material used to synthesize FeCl₃, Fe₂O₃, and many other iron compounds in the chemical and pharmaceutical industries.
✅ Laboratory & Research
Used as a standard substance in chemical analysis and for the synthesis of iron complexes.
ion" id="Part_2_FeCl%E2%82%83_%E2%80%93_Sat_III_Ferric_Chloride"> Part 2: FeCl₃ – Ferric Chloride
2.1 Basic Information
| Specifications | Value |
|---|---|
| Chemical Name | Iron(III) Chloride / Ferric Chloride |
| Other Names | Ferric Chloride |
| Formula | Iron(III) chloride |
| CAS Number | 7705-08-0 |
| Molar mass | 162.20 g/mol |
| Commercial content / Purity | 36–42% (solution) |
| Common sources | Vietnam, China |
| Packaging | 30 kg can / 200 kg drum / IBC tank / Tank truck |
2.2 Physical Properties
- Anhydrous form: Dark brown to black crystals, density 2.90 g/cm³, melting point 306°C, boiling point 315°C.
- Solution form 40%: Yellowish-brown to reddish-brown liquid with a faint odor of HCl.
- Highly soluble in water: 92 g/100 mL (20°C).
- pH of a 0.1 M solution ≈ 1.8 (strong acid).
2.3 Chemical Properties
FeCl₃ is a strong Lewis acid (electron-pair acceptor) and an effective oxidizing agent:
Reacts with metallic copper (an important reaction in PCBs):
2FeCl₃ + Cu → 2FeCl₂ + CuCl₂Reaction with bases:
FeCl₃ + 3NaOH → Fe(OH)₃↓ (nâu đỏ) + 3NaClHydrolysis reaction:
Fe³⁺ + 3H₂O → Fe(OH)₃ + 3H⁺2.4 Applications of FeCl₃
✅ Water & Wastewater Treatment — Top application
>FeCl₃ is the world’s leading coagulation agent for water treatment. When added to water, Fe³⁺ ions hydrolyze to form colloidal Fe(OH)₃, which is capable of adsorbing and flocculating suspended particles, microorganisms, phosphates, and colorants.
Mechanism of Action:
- Coagulation: Fe³⁺ neutralizes the negative charge of suspended particles
- Flocculation: Particles aggregate into large flocs
- Separation: Flocs settle to the bottom or are filtered out
Advantages over other methods of coagulation:
- Effective over a wide pH range (5–9)
- Reduces phosphate to very low levels (< 0.1 mg/L)
- Removes color and odor from Textile Dyeing wastewater
- Sludge conditions allow for easier dewatering
Specific applications:
- Municipal wastewater treatment plants
- Industrial Wastewater Treatment (paper, textile, and chemical plants)
- Eutrophication control in lakes and rivers
- Landfill leachate treatment
- Sludge thickening and dewatering (sludge conditioning)
✅ Electronic Circuit Board Etching (PCB Etching)
This is a classic application of FeCl₃ in the electronics industry. FeCl₃ and 40% are used to remove unwanted copper from the surface of printed circuit boards (PCBs), creating precise electrical pathways.
Copper etching reaction:
2FeCl₃ + Cu → 2FeCl₂ + CuCl₂Advantages in PCB etching:
- Operates at room temperature (no heating required)
- Does not react with photoresist or toner transfer
- Controllable etching rate: 0.025–0.05 mm/min
- Visual feedback: fresh solution is amber → turns dark blue when saturated
✅ Metal surface treatment & Electroplating
- Cleaning and activating steel surfaces prior to Electroplating
- Etching designs on metal for art and craftsmanship
✅ Chemical catalysis
FeCl₃ is an important Friedel-Crafts catalyst in industrial organic synthesis, particularly in the production of pharmaceuticals, printing inks, and polymers.
✅ Textile Dyeing Industry
Used as an oxidizing agent in black aniline dyeing to produce durable brown and black colors on fabric.
Section 3: Comparison of FeCl₂ and FeCl₃
| Criteria | FeCl₂ (Iron II) | FeCl₃ (Iron(III)) |
|---|---|---|
| Iron Valence | +2 (Ferrous) |
Select FeCl₂ when:
- Wastewater Treatment for hydrogen sulfide (H₂S) — FeCl₂ effectively precipitates iron sulfide
- A lower-cost chemical with acceptable performance is required
- Textile Dyeing applications (color fixation)
Choose FeCl₃ when:
- Water treatment requiring thorough phosphate removal
- PCB etching
- Colored wastewater treatment (Textile Dyeing and paper industry wastewater)
- Rapid coagulation is required
Section 4: Safety Instructions
Mandatory protective equipment
- 🧤 Thick nitrile gloves
- 🥽 Chemical-resistant safety goggles
- 👔 Apron or protective clothing
- 😷 Face mask (if handling large quantities)
- 💨 Work in a well-ventilated area
Important notice
- FeCl₃ is highly acidic (pH ~1.8) and causes severe skin and eye corrosion
- Avoid contact with metal—it corrodes most common metals
- Store in HDPE plastic or glass containers; avoid using metal
- Do not mix with strong alkalis or strong reducing agents
Spill Response
- Contain the spill area
- Neutralize with Soda Ash (
First aid in case of contact
- From: Rinse immediately with clean water for ≥15 minutes
- Eye: Rinse continuously with clean water for ≥20 minutes; seek medical attention
- If Swallowed: Do not induce vomiting; drink plenty of water; seek immediate medical attention
Section 5: Storage & Transportation
| Factor | Requirements |
|---|---|
| Storage Temperature | 5–35°C |
| Environment | Dry, cool, and away from direct sunlight |
| Packaging | HDPE cans, plastic drums, IBC tanks |
| Storage | Keep away from alkalis, metals, and flammable materials |
| ADR Classification | Corrosive — Class 8 |
| Transport | Comply with regulations for the transport of hazardous chemicals |
Section 6: Frequently Asked Questions (FAQ — AEO Optimized)
How do FeCl2 and FeCl3 differ?
FeCl₂ contains ferrous iron (Fe²⁺), which is reducing in nature and has a pale yellow color. FeCl₃ contains ferric iron (Fe³⁺), which is a strong oxidizing agent, has a reddish-brown color, and exhibits higher coagulation efficiency. FeCl₃ is more commonly used in water treatment and PCB etching.
FeCl3 What is it used for in Wastewater Treatment?
FeCl₃ is a coagulation agent; when added to water, Fe³⁺ ions hydrolyze to form Fe(OH)₃, a colloidal form that traps suspended particles, color, odor, and phosphates, which then settle or are filtered out. Effective in industrial and domestic wastewater treatment and for controlling eutrophication.
How are FeCl3 and 40% used in PCB etching?
Immerse the copper circuit board (with resist applied to the areas to be retained) into a solution of FeCl₃ 40%. Reaction: 2FeCl₃ + Cu → 2FeCl₂ + CuCl₂ removes the exposed copper, leaving only the circuit traces as designed. At room temperature (25–32°C), the etching time is approximately 10–30 minutes, depending on the concentration and thickness of the copper.
Can FeCl2 replace FeCl3 in water treatment?
Yes, but it is less effective. FeCl₂ is suitable when it is necessary to remove sulfides (H₂S) from wastewater. For the removal of phosphates or color treatment, FeCl₃ remains the preferred choice.
Where can I buy FeCl2 and FeCl3 in Vietnam?
Many industrial chemical suppliers in Vietnam distribute FeCl₂ and FeCl₃, including Loc Thien Chemicals, VietChem, Hanimex, Ngọc Gia Nguyễn, and Sài Gòn Chem. You should choose
The supplier has clear COA and MSDS documentation, and the product quality is guaranteed.What is the dosage of FeCl3 for Wastewater Treatment?
It depends on the pollutant load. Typically, 20–200 mg/L for municipal wastewater and 100–500 mg/L for concentrated industrial wastewater. A Jar Test is required beforehand to optimize the specific dosage.
Is FeCl3 toxic?
FeCl₃ is not acutely toxic when ingested at low doses but is corrosive to the skin and eyes. In aquatic environments, high concentrations may be harmful. Proper treatment is required before discharge into the environment.
Section 7: Relevant Standards & Certifications
When purchasing FeCl₂ or FeCl₃ for industrial purposes, request that the supplier provide:
- Certificate of Analysis: Confirmation of content / purity
- MSDS/SDS (Safety Data Sheet): Comprehensive safety guidelines
- ZDHC Certification (for the textile industry): Ensures the absence of hazardous chemicals in the textile supply chain
- ISO 9001: Supplier Quality Management System Certification
- Hazardous Chemicals Business License in accordance with Decree 113/2017/NĐ-CP
Conclusion
FeCl₂ and FeCl₃ are two essential industrial chemicals, each with its own specific application strengths:
- Iron(II) chloride is suitable for wastewater treatment with high sulfur content, as well as in the Textile Dyeing and Electroplating industries, at a lower cost
- Iron(III) chloride is the top choice for large-scale water/wastewater treatment, PCB etching, and applications requiring highly effective phosphate coagulation
Selecting the correct type and concentration, combined with a reputable supplier that provides all necessary documentation, will help optimize costs and treatment efficiency in industrial production.