Every activated carbon product starts as the same thing: a carbonized raw material activated into a porous adsorbent. What separates the products on a supplier's price list is mostly physical format. Granules, powder, pellets, sintered blocks, and woven cloth all adsorb through the same mechanism, but they behave completely differently in a real system: different pressure drop, different contact kinetics, different handling, different replacement logic.
Format is the first decision in any activated carbon purchase, before grade, before source material, before price. This guide walks through all five formats, what each is actually built for, and how to pick between them. The size ranges below reflect the formats Carbeva stocks and ships.
Why Format Matters as Much as Grade
A carbon's grade determines how much it can adsorb. Its format determines whether your system can use that capacity at all. Put fine powder in a flow-through filter bed and it packs solid, choking the flow. Put coarse granules in a batch decolorization tank and the kinetics are too slow to finish the job in the available contact time. Neither failure has anything to do with quality. The material was simply the wrong shape for the process.
"Grade tells you how much the carbon can capture. Format tells you whether your process will ever give it the chance."
Carbeva Technical Notes
Granular Activated Carbon (GAC)
GAC consists of irregular granules, typically specified by mesh range such as 8x30 or 12x40, roughly 0.4 to 2.4 millimeters. It is the workhorse of flow-through systems: water treatment vessels, point-of-entry home filters, and air treatment beds. Fluid flows through a packed bed of granules, and contaminants adsorb along the way. GAC balances two competing needs, enough surface exposure for adsorption and enough space between particles to keep pressure drop manageable, and it can often be reactivated and reused, which matters at industrial scale.
Powdered Activated Carbon (PAC)
PAC is milled fine, typically 100 to 325 mesh, roughly 44 to 149 microns. It is not used in packed beds. Instead it is dosed directly into a liquid, mixed for a defined contact time, and then removed by settling or filtration. The fine particle size gives PAC very fast adsorption kinetics, which is why it dominates batch processes: decolorizing sugar syrups and glycerin, treating seasonal taste and odor events in municipal water, and purification steps in food and pharmaceutical production. It is a single-use format: once spent, it leaves with the filter cake.
Activated Carbon Pellets
Pellets are extruded cylinders, usually 1 to 4 millimeters in diameter, with uniform shape and size. That uniformity is the point: a pellet bed packs consistently, producing low and predictable pressure drop, which makes pellets the preferred format for air and gas-phase systems where a fan or blower pays for every unit of resistance. Pellets are also mechanically hard and low-dust, so they survive handling, deep beds, and vibration better than granules.
Carbon Block
Carbon block is fine carbon powder fused with a binder into a solid porous form, most familiar as the cartridge inside point-of-use water filters. Because water is forced through the block's fine, continuous pore structure, a block combines adsorption with mechanical particle filtration in a single stage, often rated down to defined micron levels. The trade-offs are a higher pressure drop than any loose-media format and no possibility of topping up or reactivating: when a block is spent, the cartridge is replaced.
Activated Carbon Cloth, Felt and Sheets
Carbon cloth and felt are activated carbon in textile form, produced by carbonizing and activating a woven or non-woven fabric. The format puts the entire adsorbent within microns of the passing air stream, giving fast kinetics in a thin, flexible, cuttable layer. It appears where space and weight are constrained: respirator and mask layers, cabin air filters, odor-control inserts, wound dressings, and flat filter sheets for equipment housings. Capacity per unit is small compared to a granular bed, so cloth suits polishing and short-life applications, not bulk loads.
All Five Formats at a Glance
Here is the full comparison in the order buyers usually evaluate it.
| Parameter | GAC | PAC | Pellets | Block | Cloth / Felt |
|---|---|---|---|---|---|
| Typical size | 8x30 to 12x40 mesh | 100 to 325 mesh | 1 to 4 mm dia. | Molded cartridge | Sheet / roll |
| How it's used | Packed flow-through bed | Dosed into liquid, then removed | Packed bed, mainly gas phase | Pressure-driven cartridge | Thin layer in an assembly |
| Adsorption kinetics | Moderate | Fastest | Moderate | Fast at low flow | Fast, low total capacity |
| Pressure drop | Low to moderate | Not bed-applicable | Lowest for beds | Highest | Low per layer |
| Dust and handling | Some fines | High, needs dust control | Lowest dust | None in service | None |
| Reusable / reactivatable | Yes, at scale | No, single use | Yes, at scale | No, replace cartridge | No, replace layer |
| Typical applications | Water treatment, POE filters | Decolorization, taste and odor, food and pharma | Air and gas treatment, odor control | POU drinking water | Masks, cabin air, equipment inserts |
How to Choose: Start From the Process, Not the Product
The reliable way to pick a format is to describe your process first. Continuous flow through a vessel points to GAC for liquids or pellets for gas. A batch tank with mixing and downstream filtration points to PAC. A compact point-of-use device points to block. A thin layer inside a wearable or an equipment housing points to cloth. Only after the format is fixed does it make sense to compare grades, iodine numbers, and source materials within that format, because a spec comparison across formats is comparing products that will never compete for the same job.
| GAC | PAC | Pellets | Cloth |
| 8x30 mesh | 100–325 mesh | 1–4 mm | Sheet form |
Common Mistakes When Choosing a Format
- Buying by price per kilogram across formats. PAC is often cheapest per kilo, but it cannot do a packed-bed job at any price.
- Using GAC where PAC kinetics are needed. Batch decolorization with coarse granules runs out of contact time long before it runs out of capacity.
- Ignoring pressure drop in gas-phase systems. Granules in a deep air bed can cost more in fan energy than pellets cost in media premium.
- Assuming all formats can be reactivated. Only bulk GAC and pellets realistically return for reactivation; PAC, blocks, and cloth are replace-only.
- Ordering a format without confirming your downstream separation. PAC needs a settling or filtration step to leave the process; without one, it ends up in your product.
Ordering Samples Across Formats
If you are genuinely between two formats, the fastest resolution is to test both under your real operating conditions. Tell us your process, flow or batch, liquid or gas, contact time available, and the contaminant you are targeting, and we will recommend a format and grade, then ship samples with each batch's tested specs attached so the comparison is settled by data rather than by catalog copy.
Frequently Asked Questions
What are the main types of activated carbon?
Five physical formats cover nearly all applications: granular activated carbon (GAC), powdered activated carbon (PAC), extruded pellets, sintered carbon block, and activated carbon cloth or felt. All adsorb the same way; they differ in particle size, structure, and how a system uses them.
What is the difference between GAC and PAC?
GAC is coarse granules used in packed flow-through beds and can often be reactivated. PAC is fine powder dosed directly into liquids for fast batch treatment, then removed by settling or filtration and discarded.
Are pellets better than granules?
For gas-phase and air treatment, usually yes: uniform pellets produce lower pressure drop and less dust. For liquid-phase beds, granules remain the standard. Neither is better in the abstract; the process decides.
Which type of activated carbon is best for home water filters?
Point-of-use drinking water filters typically use carbon block for combined adsorption and particle filtration, while whole-house point-of-entry systems typically use GAC beds for higher flow at low pressure drop.