Ferric Chloride
FeCl3 · 30–150 mg/L
High-performance coagulant for high-turbidity, high-COD industrial effluent. Precipitates phosphate as FePO4 (optimal pH 5–7), strips heavy metals such as chromium and zinc, removes colour, and doubles as a sludge-thickening aid — forming dense, fast-settling flocs.
Specifications
| Chemical Formula | FeCl3 |
|---|---|
| Primary Function | Coagulant for high-turbidity, heavy metal & phosphate removal |
| Physical Form | Dark liquid / anhydrous solid |
| Application Point | High-COD primary ETPs / sludge pits |
| Typical Dosage | 30–150 mg/L |
| Phosphate Removal | Optimal at pH 5–7 |
| Packaging | Carboys / drums / tankers |
Where it's used
- High-COD Industrial ETPs
- Phosphate Removal
- Heavy Metal Precipitation
- Sludge Thickening
- Colour Removal
Related solutions
What it is and when to use it
Ferric chloride (FeCl₃) is an iron-based coagulant for difficult industrial effluent with high turbidity, high COD, phosphate or heavy metals. Use it when PAC or alum cannot achieve the required clarity, or when phosphate precipitation and metal removal are needed, with heavy, fast-settling flocs.
Ferric chloride hydrolyses to form ferric hydroxide flocs, which are dense and settle quickly. It precipitates phosphate as ferric phosphate (FePO₄), most effectively at pH 5–7, and helps remove metals such as chromium and zinc. It is also used as a sludge-conditioning and thickening aid.
It is strongly acidic and corrosive, so it consumes alkalinity and lowers pH. Downstream pH correction is often needed, and storage and dosing equipment must be made of corrosion-resistant materials such as FRP, HDPE or rubber-lined steel. It is supplied as a dark liquid or anhydrous solid in carboys, drums or tankers. The typical dosage is 30–150 mg/L, but confirm it by jar test.
Use it for
- High-COD, high-turbidity industrial effluent in primary treatment
- Chemical phosphate removal
- Heavy metal precipitation, including chromium and zinc
- Sludge thickening and conditioning
How to choose
- Jar-test ferric chloride against PAC to compare clarity, sludge volume and cost
- Allow for alkalinity consumption and plan pH correction if needed
- Use corrosion-resistant storage tanks, pumps and piping
- Choose liquid or solid form based on volume and handling capability
- Consider colour: iron residuals can tint water if dosing is poorly controlled
Frequently asked questions
When should I use ferric chloride instead of PAC?
Use ferric chloride for heavy industrial effluent with high COD and turbidity, when you need chemical phosphate removal, or when heavy metals must be precipitated. PAC is usually preferred for general clarification and drinking water, where its wider pH window and lower sludge volume matter. A jar test comparing both on your effluent will show the better option.
Does ferric chloride affect pH?
Yes. Ferric chloride is strongly acidic and consumes alkalinity as it reacts, so pH drops after dosing. In low-alkalinity water, that can take pH outside the optimum range for coagulation or downstream biology. Monitor pH after the flash mixer and add caustic soda or lime if correction is needed.
How should ferric chloride be stored and handled?
Ferric chloride is corrosive to most metals, so store and dose it using FRP, HDPE, PVC or rubber-lined equipment. Operators should wear chemical-resistant gloves, goggles and aprons, and spills should be contained and neutralised. Follow the safety data sheet supplied with the product.
Technically reviewed by Prashant Dwivedi, Co-Founder & Director ·