Ferrous Sulfate Heptahydrate
FeSO₄·7H₂O
Ferrous sulfate heptahydrate is a crystalline iron(II) salt (FeSO₄·7H₂O, minimum 98% purity) supplied as pale blue crystals. It is used as a water and wastewater coagulant, as a reducing agent for hexavalent chromium, and as a cement additive for chromate reduction. CHIMI ART supplies the product from Egypt in 25 kg and 50 kg bags or in bulk, with a certificate of analysis.
Product Overview
Ferrous sulfate heptahydrate is a crystalline iron(II) salt (FeSO₄·7H₂O, minimum 98% purity) supplied as pale blue crystals. It is used as a water and wastewater coagulant, as a reducing agent for hexavalent chromium, and as a cement additive for chromate reduction. CHIMI ART supplies the product from Egypt in 25 kg and 50 kg bags or in bulk, with a certificate of analysis.
Technical Specifications
- Chemical Formula
- FeSO₄·7H₂O
- CAS Number
- 7782-63-0
- Appearance
- Pale blue crystalline powder
- Concentration
- ≥ 98% FeSO₄·7H₂O
- Specific Gravity
- 1.90 (solid)
- pH Range
- 3.0-5.0 (1% solution)
- Solubility
- Water soluble
- Available Packaging
- 25kg bags · 50kg bags · Bulk
- Shelf Life
- 24 months
- Storage Conditions
- Dry, cool place
| Property | Value |
|---|---|
| Chemical Formula | FeSO₄·7H₂O |
| CAS Number | 7782-63-0 |
| Appearance | Pale blue crystalline powder |
| Concentration | ≥ 98% FeSO₄·7H₂O |
| Specific Gravity | 1.90 (solid) |
| pH Range | 3.0-5.0 (1% solution) |
| Solubility | Water soluble |
| Available Packaging | 25kg bags · 50kg bags · Bulk |
| Shelf Life | 24 months |
| Storage Conditions | Dry, cool place |
Applications
Dosing Guidelines
Dissolve the crystals in water before application — typically in a stirred make-down tank using non-metallic or lined equipment — and dose the resulting solution with a metering pump. Typical coagulation doses are in the range of 100-500 mg/L depending on the application and water characteristics, with the site-specific optimum set by jar testing. For chromium reduction, the dose is established against the measured Cr(VI) load and confirmed analytically; for cement addition, follow the plant's mix design and verify soluble chromate in the finished product.
How It Works
Dissolved in water, ferrous sulfate heptahydrate releases Fe²⁺ ions that neutralise the negative charges stabilising colloidal particles, letting them collide and grow into flocs; reaction with alkalinity forms iron hydroxide precipitates that enmesh remaining fines, and any oxidation to the ferric state produces denser, faster-settling floc. As a reducing agent, Fe²⁺ converts toxic, mobile hexavalent chromium, Cr(VI), to the far less soluble trivalent form, Cr(III), which can then be precipitated as hydroxide and removed with the sludge — the basis of chromium treatment in metal-finishing effluents. The same reaction is used in cement manufacture, where a small addition of ferrous sulfate reduces soluble chromates in the finished cement. Jar or bench testing establishes the effective dose for each duty.
Usage Tips
Store ferrous sulfate heptahydrate in a dry, cool place in tightly closed bags; correctly stored, shelf life is 24 months. The crystals absorb moisture and can cake, and on prolonged exposure to humid air the surface slowly oxidises and discolours, so reseal opened bags and keep them on pallets off damp floors. Prepare solutions in corrosion-resistant equipment, avoid dust generation during handling, and wear gloves, eye protection and a dust mask when charging make-down tanks. Wash spills away with plenty of water.
Certifications & Compliance
Frequently Asked Questions
Why is ferrous sulfate heptahydrate added to cement?
It acts as a reducing agent for soluble chromates in cement, converting hexavalent chromium, Cr(VI), to the far less soluble trivalent form, Cr(III). This addition is widely applied to limit the soluble chromate content of finished cement for the protection of handlers, with the dose set in the plant's mix design and verified analytically in the product.
How does ferrous sulfate remove hexavalent chromium from wastewater?
The Fe²⁺ ion reduces Cr(VI) to Cr(III), which is then precipitated as hydroxide under pH control and removed with the sludge. The dose is set against the measured chromium load and removal is confirmed by laboratory analysis of the treated effluent — a standard approach in plating and metal-finishing wastewater.
How should the crystals be prepared for dosing at a treatment plant?
Dissolve the crystals in a stirred make-down tank built from non-metallic or lined materials, then dose the resulting solution with a metering pump at a point of good mixing. The optimum dose is determined by jar testing on the actual water and re-checked as water quality changes.
How do I keep the product free-flowing during storage?
Keep bags tightly sealed in a dry, cool store on raised pallets, and reseal any opened bag immediately — the crystals are hygroscopic and cake when they take up moisture. Correctly stored, shelf life is 24 months; rotate stock on a first-in, first-out basis.
What purity is supplied and how is it documented?
The product is supplied with a minimum FeSO₄·7H₂O content of 98%, and a certificate of analysis documenting the batch parameters accompanies every delivery. The Technical Data Sheet (TDS) and Safety Data Sheet (SDS) are available on request or from the product page.
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