I think the powdered activated carbon is better due to its' higher specific surface area.

Powder or granular should not change (much) the surface area.

Powdered carbons are easy to be used in laboratory studies (mount in small reactors, place in analysis equipment, etc), however, its difficult to use them in industrial applications or pilot plants (slower diffusion through particles and high pressure loss across the bed). That's why in industry granular porous samples are always used: better mechanical by sacrificing some efficiency.

So in general, powder for lab and higher rates, and granular for industry but more or less useless where you want fast rates.

Fernando is correct - the active surface is almost entirely within the pore, with relatively little on the surface of the particle.  For this reason a given carbon has about the same active area whether in granular or powdered form.  In general, powedered carbons  are used only for batch treatment of liquids - otherwise granular carbons are used.

It does not matter whether it is in granular or powdered form. The important things are pore size and pore volume of the porous carbon. It has been shown that fine micropores (0.4 cm3/g) of fine micropores would be the best candidate for CO2 adsorption. See following articles for more details.

http://pubs.rsc.org/en/content/articlelanding/2013/ta/c2ta00388k#!divAbstract

http://pubs.acs.org/doi/abs/10.1021/am400112m?prevSearch=nilantha&searchHistoryKey=

http://pubs.acs.org/doi/abs/10.1021/cm5001895?prevSearch=nilantha&searchHistoryKey=

http://www.sciencedirect.com/science/article/pii/S0008622313007963

For adsorption performance, Nilantha is right, powdered or granular doesn't matter.  The issue is pressure drop, which is too high for powdered carbon to be packed into a column.  Larger particle size granular carbons are used to treat gases because the higher diffusivity in the gas (vs. in a liquid) allows use of the larger particle, with the benefit of lower pressure drop.  Powdered carbons are used to treat liquids in a batch process.

Another form of carbon sorbents are the fibers. Their hydrodynamic resitance is lower than that of particles of the same diameter. Has anyone interest to check the performance of nanoporous (D~0.6 nm) carbon fibers? Is so, send a mail to [email protected]

Yes, the regeneration of sorbent is unimportant if the material is cheap or even vey cheap.

GAS is efficient for Gas adsorption practice. Because, if PAS is used the contaminated air will form a cloud or dust of powdered activated carbon, this makes the researcher to install precipators (cotroll's) to precipate the soot materials due to powdered form of Activated carbon or very fine filteres are to be installed. If it is a granualar, these type of practical dificulties will be over come. The granualar form is better than powered form.

I agree with what has been said about pressure drop. This factor and the practical difficulties of handling the powdered form when trying to pass a gas through it is the key. GAC is always the first choice for ambient and industrial air monitoring for organics unless thermal desorption is to be used. There is a good reason for that.

It really depends on what types of reactors/adsorbers you are going to choose. Each type of activated carbon has its own advantages and disadvantages. 

In general, GAC or pelleted AC is recommended and used due to favorable pressure drop. However, choice  depends on size of an adsorber, amount of adsorbent used, conditions (pressured or not), static or flow adsorber. Jacek

For acid gas adsorption I don't know how efficient is activated carbon as adsorbent.

You may need to be impregnated the powdered AC with organic (monoethanolamine, MEA) or inorganic (KOH) bases. 

PAC is alright for using in a gas scrubber, pressure drop would not be an issue for fluid like gas. 

Dear Antonio,

Please try to choose granular AC since its operation is much easy or reactor or adsorber management cost is lower.   

If Some  granular ACs have very high surface areas.

It is better to use sulphuric acid activated coconut shell activated carbon which is having more pores and very effective activation site in amorphous and granular form and it proves to be very efficient and harmless and easily recharged and commercially available comparatively it is economic cost.  

Try to surface modifies the activated carbon by silanation or by doping material like palladium, that may be a good adsorbent for gas separation

powdered AC may have good adsorption property that granular, as the particle size decreases, the surface area increases and adsorption rate increases.

Debashis I respectfully disagree with your answer, but you are not alone in this misconception.  Smaller particles do not provide greater surface area because the vast majority of areas for adsorption is in the internal pores, not the external surface.  The advantage of smaller particles is mass transfer - that is, the diffusion path is shorter, so molecules to be adsorbed can reach available adsorption sites faster.  This is useful with liquids, in which diffusivity is lower than with gases.  For gases, larger particles can be used, lowering pressure drop, because diffusivity is higher.  To the original question, powdered carbon is used only for liquids, in batch - it cannot be used in a continuous column because the pressure drop is too high.  GAC is used for gases.  Hope this helps!

Granular activated carbon is recommended to reduce pressure drop in the adsorption bed. Of course the specific surface are of the adsorbent is not a function of particle size since we are dealing with a highly porous material.   

granular activated carbon is a better option for gas absorption due to the as gheir diffusion rate into the granular particles is fatser than in powdered  carbon. see this link: http://www.newworldencyclopedia.org/entry/Activated_carbon

It totally depends on the process you plan to use. In packed beds you can only use granulated material. If, however, you have both a very large gas volume (around 100.000 m³/h or thereabouts) *and* a fairly high adsorption, so that one equilibrium step would be enough, you can inject powdered carbon into the gas stream, have it fly with the gas and filter it out in the end. This is only done for some special indurstial application, your garden vartiety air purification filter always has granulated carbon.

Dear Antonio, More is the surface area, pore volume , more is the adsorption. So you should choose the AC whose surface area is more. Eg: Darco type

Powdered AC with very high surface area and higher total volume contributed by the micro-porosity would be the best choice but for packing in a column it needs to be converted into pellet using suitable binder. Impregnated by alkali will improve the quality of AC for CO2 adsorption. 

Why pellet, see the link

file:///C:/Users/Amina/Downloads/ijms-13-08388.pdf