Packed columns utilizing filter media for chemical exchange are the most common devices used in the chemical industry for reactant contact optimization. Packed columns are used in a range of industries to allow intimate contact between two immiscible/partly immiscible fluids, which can be liquid/gas or liquid/liquid. The fluids are passed through a column in a countercurrent flow. 
In the column it is important to maintain an effective mass transfer, so its essential that a packing is selected which will support a large surface area for mass transfer.