Choosing the wrong iron coagulant not only affects treatment performance—it directly increases your chemical dosage costs, raises sludge volume, and puts your discharge permit at risk with QCVN 40:2011/MONRE industrial wastewater or QCVN 14:2008/BTNMT (domestic wastewater). Yet FeCl2 (ferrous chloride) and FeCl3 (ferric chloride) are routinely confused at the procurement stage, leading to plant upsets that take weeks to correct.
This guide compares both iron coagulants side by side—chemistry, operating conditions, optimal use cases, available specifications in Vietnam, and how to source them with full ZDHC/MSDS documentation from a reliable local supplier.
FeCl2 vs. FeCl3: Key Chemical Differences
Ferrous chloride (FeCl2) and ferric chloride (FeCl3) are both iron-based coagulants derived from hydrochloric acid treatment of iron, but they carry iron in different oxidation states — Fe²⁺ and Fe³⁺ respectively — and this single difference drives very different behavior inside a treatment system.
FeCl2 — Ferrous Chloride (Fe²⁺)
- Molecular weight: 126.75 g/mol
- Iron oxidation state: +2 (divalent)
- Color in solution: Light green to pale yellow
- Requires dissolved oxygen or a co-oxidant (e.g., Cl₂, H₂O₂) to convert Fe²⁺ → Fe³⁺ for effective floc formation at higher pH
- Effective coagulation pH: 8.5 – 11 (best in alkaline conditions)
- Produces a denser, faster-settling sludge when operated correctly
- CAS Number: 7758-94-3
Ferric Chloride (Fe³⁺)
- Molecular weight: 162.20 g/mol
- Iron oxidation state: +3 (trivalent)
- Color in solution: Dark amber to brown
- Hydrolyzes spontaneously to form Fe(OH)₃ floc without additional oxidant
- Effective coagulation pH: 5.0 – 9.0 (wider range; works in acidic conditions)
- Reacts faster; lower dosage typically needed compared to FeCl2 for equivalent TSS removal
- CAS Number: 7705-08-0
The fundamental rule: FeCl3 is the more versatile coagulant for most wastewater streams. FeCl2 is the preferred choice when your process operates at high alkalinity, or when you are targeting specific contaminants such as sulfides or certain heavy metals that benefit from a reducing iron environment.
FeCl2 (Ferrous Chloride) is primarily used for the following purposes: * **Wastewater Treatment:** It's a common reducing agent and precipitating agent used to remove pollutants from industrial and municipal wastewater. * **Phosphate Removal:** FeCl2 reacts with phosphates to form insoluble iron phosphates that can be easily removed. * **Sulfide Removal:** It effectively precipitates hydrogen sulfide (H₂S) as ferrous sulfide (FeS), which helps control odor and prevent corrosion. * **Heavy Metal Removal:** It can help precipitate certain heavy metals from wastewater. * **Flocculation:** In water treatment, FeCl2 can act as a coagulant, causing small suspended particles to clump together into larger flocs that are easier to settle out. * **Chemical Intermediate:** It serves as a precursor in the production of other iron compounds. * **Pigments:** It is used in the manufacturing of certain pigments. * **Dyeing and Printing:** In the textile industry, it can be used as a mordant to help dyes adhere to fabrics. * **Reduction Agent:** In various chemical processes, it's employed as a reducing agent. * **Catalyst:** In some specific chemical reactions, it can function as a catalyst. It's important to note that while ferric chloride (FeCl3) is more commonly used for many of these applications, ferrous chloride (FeCl2) has specific advantages in certain situations, particularly when a milder reducing agent or precipitant is needed.
FeCl2 is the coagulant of choice in three principal application scenarios in Vietnam’s industrial wastewater sector:
Textile Dyeing and Finishing Wastewater
Vietnam’s textile industry—concentrated in provinces such as Bình Dương, Đồng Nai, and Long An—generates highly alkaline wastewater with pH values often ranging from 9 to 12 after the desizing and scouring steps. In this alkaline environment, FeCl2 oxidizes in situ to Fe(OH)3 floc without needing additional acidification, making it cost-effective where pH adjustment chemicals would otherwise be required. It is particularly effective at adsorbing reactive dyes and azo dye intermediates onto the iron hydroxide floc structure.
2. Phosphorus Removal (Biological + Chemical Combination)
In activated sludge processes for BOD removal, FeCl2 is often dosed directly into the aeration tank or at the outlet of a secondary clarifier to precipitate soluble phosphate as vivianite (Fe₃(PO₄)₂). The reaction under aerobic conditions produces an insoluble Fe-P complex that exits in the waste sludge. Effluent total phosphorus can be reduced to below 4 mg/L, the threshold required under QCVN 40:2011, Column B.
3. Sulfide and Heavy Metal Control
In industrial parks where electroplating, metal surface treatment, or leather tanning processes generate sulfide-laden wastewater, FeCl2 reacts with sulfide ions to precipitate FeS. This serves as both a coagulation step and a chemical oxidation/precipitation step. Similarly, in moderately alkaline conditions, FeCl2 aids in the co-precipitation of heavy metals such as cadmium (Cd²⁺) and lead (Pb²⁺).
Practical note for Vietnam operations: FeCl2 in liquid form degrades faster than FeCl3 when exposed to air. Oxidation to FeCl3 occurs over time, which changes the product's behavior. Always store drums sealed and use within the supplier's stated shelf life. Request MSDS documentation to confirm storage protocol.
When to Use FeCl₃ (Ferric Chloride)
FeCl3 is the dominant iron coagulant in global wastewater practice, and for good reason: it works across a wide pH range, reacts quickly, and produces a robust floc that settles well in standard clarifiers.
1. PCB (Printed Circuit Board) Etching in Electronics Manufacturing
The electronics manufacturing sector in Vietnam — anchored by Samsung, Intel, and hundreds of component suppliers in Hanoi, Thai Nguyen, and Ho Chi Minh City — uses FeCl3 as the primary etchant to selectively dissolve unwanted copper from PCB substrates. The reaction is:
2 FeCl₃ + Cu → 2 FeCl₂ + CuCl₂
Concentration for PCB etching: typically 36–40% w/v liquid solution. Spent etchant is recovered for copper extraction, and the residual FeCl2/FeCl3 mixture is then treated in the wastewater system. Suppliers like Loc Thien Chemical ship FeCl3 in IBC tanks (1,000 L) or drums (200 L) to electronics parks in the North and South.
2. Municipal and Mixed Industrial Wastewater
For wastewater treatment plants serving mixed-source industrial zones (food processing + light manufacturing + domestic), FeCl₃ provides reliable TSS, BOD, and phosphorus removal across the variable influent quality these plants encounter. It can be dosed at pH 6–8 without auxiliary alkalinity addition in most cases, simplifying operations.
3. Color and Turbidity Removal
FeCl3 is significantly more effective than FeCl2 for color removal from surface water and from wastewater containing humic substances, tannins, or direct/reactive dyes at acidic-to-neutral pH. The higher charge density of Fe³⁺ destabilizes colloidal color particles more effectively.
Practical note: FeCl₃ is strongly acidic (pH of a 36–40% solution ≈ 1–2). Handle with full PPE—face shield, acid-resistant gloves, rubber boots. Never add water to concentrated FeCl₃; always add FeCl₃ to the dilution water. The MSDS must be available on-site before handling.
FeCl2 vs FeCl3: Side-by-Side Comparison Table
| Parameter | Ferrous Chloride | Ferric Chloride |
|---|---|---|
| Iron Oxidation State | Fe²⁺ | Fe³⁺ |
| Effective pH Range | 8.5 – 11.0 | 5.0 – 9.0 |
| Typical Liquid Concentration (Vietnam) | 25 – 30% w/v | 36 – 40% w/v |
| Typical Dosage (wastewater) | 150 – 400 mg/L | 50 – 200 mg/L |
| Floc Settling Speed | Moderate – Fast (in alkaline conditions) | Fast |
| Sludge Volume | Lower (denser floc) | Moderate |
| Colour Removal Efficiency | Moderate | High |
| Phosphorus Removal | Good (alkaline, aeration systems) | Good (wider pH range) |
| PCB Etching Suitability | Not applicable | ✅ Primary etchant |
| Sulfido precipitation | ✅ Effective | Limited |
| Availability in Vietnam | ✅ Available (Loc Thien Chemical) | ✅ Available (Loc Thien Chemical) |
| ZDHC / MSDS Documentation | ✅ Provided | ✅ Provided |
| Relative Cost (per kg Fe) | Generally lower unit cost | Slightly higher; lower dosage compensates |
| Storage Sensitivity | Oxidizes on air exposure; keep sealed | Stable; corrosive to metals |
| Primary Use Cases Vietnam | Textile wastewater treatment, phosphorus removal, heavy metals | PCB etching, municipal WWT, colour removal |
FeCl2 and FeCl3 Supply at Loc Thien Chemical
Loc Thien Chemical (Hóa Chất Lộc Thiên) is a Vietnam-based industrial chemical distributor supplying both ferrous chloride and ferric chloride to factories, wastewater treatment plants, and electronics manufacturers across the country.
FeCl2 (Ferrous Chloride) - Product Specifications
- Product ID: 534
- Form: Liquid solution, 25–30% w/v
- Appearance: Light green to pale yellow liquid
- Primary applications: Textile dyeing wastewater treatment, phosphorus precipitation, heavy metal co-precipitation, industrial park WWTPs
- Packaging: Drums (200 L), IBC tanks (1,000 L), bulk tanker on request
- Documentation: MSDS (Vietnamese + English), ZDHC MRSL Level 1 compliance documentation available
- Product URL: https://hoachatlocthien.com/en/product/fecl2-sat-ii-clorua
FeCl3 (Ferric Chloride) — Product Specifications
- Product ID: 772
- Form: Liquid solution, 36–40% w/v
- Appearance: Dark amber/brown liquid
- Primary applications: PCB etching (electronics manufacturing), municipal and industrial WWTP coagulation, colour and turbidity removal
- Packaging: Drums (200 L), IBC tanks (1,000 L), bulk tanker on request
- Documentation: MSDS (Vietnamese + English), ZDHC MRSL Level 1 compliance documentation available
- Product URL: https://hoachatlocthien.com/en/product/fecl3-sat-iii-chloride
Delivery to Industrial Zones in Vietnam
Loc Thien Chemical operates from a warehouse and distribution facility in Ho Chi Minh City and provides scheduled and on-demand delivery of FeCl2 and FeCl3 to industrial zones and factories throughout Vietnam:
| Region | Coverage |
|---|---|
| Ho Chi Minh City | All districts; same-day or next-day delivery for standard orders |
| Binh Duong | VSIP I & II, Mỹ Phước, Đại Đăng, and other KCN — 1–2 business days |
| Dong Nai | Amata, Long Thành, Nhơn Trạch — 1–2 business days |
| Long An / Tây Ninh | 2–3 business days |
| Nationwide | Freight delivery available to all provinces; contact for schedule and MOQ |
Logistics notes:
- Both FeCl2 and FeCl3 are classified as hazardous goods for transport — all deliveries include compliant dangerous goods documentation (DG manifest, MSDS)
- IBC and drum return/exchange programme available for regular customers
- Emergency top-up deliveries available for plants facing unplanned demand spikes — call +84 979 891 929
Contact & Ordering:
📞 Hotline: +84 979 891 929
✉️ Email: locthien@locthien.vn
📍 Address: 452/6B Tỉnh Lộ 10, P. Bình Trị Đông, Q. Bình Tân, TP.HCM
Frequently Asked Questions
Ready to order FeCl2 or FeCl3 for your plant?
Whether you operate a textile dyeing WWTP, a PCB etching facility, or a municipal wastewater treatment plant, Loc Thien Chemical has the right iron coagulant, the correct concentration, and the compliance documentation your team needs.
- ✅ FeCl2 (Ferrous Chloride): Liquid 25–30%, ideal for alkaline wastewater, textile, phosphorus removal
- ✅ FeCl3 (Ferric Chloride): Liquid 36–40%, ideal for PCB etching, colour removal, general WWTP coagulation
- ✅ MSDS + ZDHC documentation included
- ✅ Delivery to HCMC, Bình Dương, Đồng Nai, and nationwide
- ✅ Same-day delivery available in HCMC
Contact our technical team today:
📞 +84 979 891 929
✉️ locthien@locthien.vn
📍 452/6B Tỉnh Lộ 10, P. Bình Trị Đông, Q. Bình Tân, TP.HCM