Granular Ferric Hydroxide (GEH)
Granular ferric hydroxide (GEH) is a porous, iron hydroxide-based adsorbent. It separates target compounds such as arsenic from water by binding them to its iron-based surfaces.
Its granular form creates an adsorption bed through which water flows. Retention capacity depends on more than grain size; surface properties and interactions with other dissolved compounds also matter.
Technical Specifications
| Mineral phases | β-FeOOH and Fe(OH)₃ |
|---|---|
| Dry solids | 58% |
| Iron in dry solids | 600 g/kg |
| Particle size range | 0.2–2.0 mm |
| Undersize fraction (upper limit) | 10% |
| Combined undersize and oversize (upper limit) | 20% |
| Backwashed bulk density | 1,150 kg/m³ |
| Specific surface area (BET) | 300 m²/g |
Application and use
- For arsenic-bearing groundwater, an adsorption bed is evaluated against the required treated-water quality.
- Water treatment for food production requires assessment of both the selected grade and the complete process.
- Phosphate and silicate in the feed are considered when assessing competing adsorption and bed life.
- Outlet sampling tracks breakthrough so replacement can be scheduled for the actual contaminant load.
Frequently asked questions
Does As(III) need a separate oxidation step?
It depends on the selected product. Some ferric-hydroxide adsorbents capture both arsenic species; As(III) oxidation can improve removal with other grades. Verify speciation and product code.
Can bed life be stated in advance as a fixed number?
No. Capacity depends on raw-water composition, operating conditions and the target outlet level. Water analysis and effluent monitoring are needed.
Can it be used when phosphate and silicate are present?
These constituents can also bind to iron-based adsorbents. Include their concentrations in the water analysis when assessing arsenic-bed life.
Does backwashing renew adsorption capacity?
No. Backwashing hydraulically removes bed fines; it does not restore exhausted adsorption capacity.
Can the material be stored dry?
It depends on the grade. Some granular ferric hydroxides must be protected from drying and sunlight; other iron-oxide adsorbents are supplied dry. Follow the supplied product instructions.