Quick answer
What is the difference between GAC and PAC?
GAC is granular and used in filter beds that the liquid flows through, which suits continuous treatment. PAC is a fine powder dosed into the liquid and filtered out afterwards, which suits batch or intermittent treatment. The material is similar; particle size decides the process.
Granular activated carbon (GAC) and powdered activated carbon (PAC) are the two most common forms of activated carbon. The material is similar; what differs is particle size, and that changes how the carbon is used.
At a glance
| GAC | PAC | |
|---|---|---|
| Form | Granules | Fine powder |
| How it is used | Fixed bed in a filter or column | Dosed into the liquid, then removed |
| Best suited to | Continuous treatment | Batch or intermittent treatment |
| Removal after use | Stays in the vessel until replaced | Settling or filtration |
| After use | Can often be reactivated | Usually disposed of with the filter cake |
When GAC is the better fit
GAC suits steady, continuous flows where a filter vessel is in place: drinking water filters, effluent polishing, process liquid columns and gas phase beds. The bed keeps working until it approaches saturation, and there is no carbon to separate from the treated liquid.
When PAC is the better fit
PAC suits processes where treatment is batch-wise or needed only some of the time. In pharmaceutical and bulk drug manufacture, PAC is charged into a solution, stirred and filtered out. In water treatment, it can be dosed during periods of taste and odour trouble without installing a dedicated carbon filter.
Because the powder is fine, it acts quickly, but it must be removed completely. A filter aid is often used for this.
Questions to ask
- Is the process continuous or batch?
- Is there an existing filter vessel, or would carbon need to be dosed?
- What exactly needs removing, and to what level?
- How will spent carbon be handled?
If you are unsure, share your process details with us and we will help you narrow down the form and grade.
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