About Filter Grade Diatomaceous Earth
Filter grade diatomaceous earth is a milled and classified diatomite used as a filter aid in pressure leaf, plate and frame, candle and rotary vacuum filters. The rigid, porous diatom fragments pack loosely, forming a cake with a high void fraction. Fine suspended solids are trapped inside the cake rather than blinding the filter cloth or screen, which keeps flow rates steady for longer.
Each permeability class is a balance between clarity and flow. Finer classes retain smaller particles and give a brighter filtrate, while coarser classes support higher throughput on liquids with a heavy solids load. We help customers select a class for a precoat layer and a body-feed dosage, based on the liquid, the filter type and the clarity target.
Typical duties include clarification of edible oils after bleaching and dewaxing, sugar and glucose syrups, chemical intermediates, plating solutions, lubricating oils and process water. The material is chemically inert across a wide pH range and does not react with the liquid being filtered. Obsidian Minerals produces filter grade diatomaceous earth in Gujarat, tests every batch in an NABL-accredited laboratory, and supplies it with a Technical Data Sheet and Certificate of Analysis. Customers using it in food-contact processes should confirm suitability against their local regulations.
Typical specifications
| Parameter | Typical Value | Test Method |
|---|---|---|
| SiO₂ | 80–90 % | XRF |
| Permeability | 0.1–2.0 Darcy (class dependent) | Internal method |
| Wet cake density | 0.30–0.45 g/cm³ | Internal method |
| Moisture | ≤ 1.0 % | Loss on drying, 105 °C |
| pH (10 % slurry) | 6.0–9.0 | Internal method |
| Fe₂O₃ | ≤ 2.0 % | XRF |
| Appearance | Off-white to light buff powder | Visual |
Typical values for guidance. Permeability class is agreed at order. Guaranteed limits are stated on the Technical Data Sheet and batch CoA.
Key features & benefits
Open, incompressible filter cake
The rigid diatom skeletons resist compression under pressure, so the filter cake stays permeable through the cycle. This keeps differential pressure rising slowly and extends run length between cleanings on many filter types.
Graded permeability classes
Filter grade diatomaceous earth is classified into permeability classes, allowing operators to choose a finer class for polishing or a coarser class where throughput and high solids loading are the priority.
Chemically inert silica
Amorphous silica does not react with oils, syrups or most process chemicals, and it contributes little colour, odour or taste. Soluble iron and other impurities are monitored batch by batch in our laboratory.
Precoat and body-feed use
The same grade can be used to form a protective precoat on septum or screen and as a continuous body feed. One material for both steps simplifies stock holding and dosing at the plant.
Applications
Edible oil filtration
Used after bleaching, winterisation and dewaxing of palm, soybean, sunflower and rice bran oils to remove spent clay, waxes and fine solids before deodorisation or packing.
Sugar and syrup clarification
Supports clarification of cane sugar liquor, glucose and other syrups where a bright, haze-free product and steady filter cycles are needed. Suitability for food processing should be verified locally.
Chemical and process liquids
Removes fine suspended matter from chemical intermediates, plating baths, lubricating oils and process water, protecting downstream equipment and improving product appearance in industrial filtration circuits.
Usage & handling
- Precoat: typically 0.5–1.5 kg per m² of filter area, applied as a slurry before the main filtration cycle.
- Body feed: typically 0.1–0.5 % of liquid weight, adjusted to solids load and target clarity.
- Slurry the powder gently; high-shear mixing breaks diatom fragments and reduces permeability.
- Store in a dry, covered area and keep bags closed to prevent moisture and dust pick-up.
Packaging & supply
- 25 kg or 50 kg HDPE or paper bags
- 1 MT or 1.2 MT jumbo (FIBC) bags
- Custom and private-label packaging on request
Frequently asked questions
How do I choose the right permeability for filter grade diatomaceous earth?
Start with your clarity target and the solids load of the liquid. Fine classes give the clearest filtrate but lower flow; coarse classes give higher throughput where clarity is less critical. We recommend a lab or pilot trial with two adjacent classes, and our team can suggest a starting point if you share your filter type and liquid details.
Can this filter aid be used for edible oil refining?
Yes. It is used in edible oil refineries to filter oil after bleaching and dewaxing and to build precoat on leaf filters. Refiners should confirm that the grade meets the food-contact requirements in their market, and we can supply the documentation needed for that review.
What is the difference between precoat and body feed?
Precoat is a thin layer of filter aid deposited on the filter septum before filtration starts. It protects the cloth and gives immediate clarity. Body feed is filter aid dosed continuously into the unfiltered liquid, keeping the growing cake porous so that pressure rises slowly and the cycle lasts longer.
Is the filter grade natural or calcined?
The process route is selected to suit the permeability class and the customer's application. The route, together with typical permeability and crystalline silica content, is stated on the Technical Data Sheet and SDS for each class. Please share your requirement and we will confirm the most suitable option.