DOWEX Ion Exchange Resins WATER CONDITIONING MANUAL

Terms, Acronyms, And Abbreviations
Term Definition
Degree of crosslinking Effective amount of crosslinking present in an ion exchange resin, normally expressed as
an equivalent amount of physical crosslinking agent (e.g., divinylbenzene).
Deionization Removal of ionizable (soluble) constituents and silica from a solution by ion exchange
processing. Normally performed by passing the solution through the hydrogen form of
cation exchange resin and through the hydroxide form of an anion exchange resin, either
as a two-step operation or as an operation in which a single bed containing a mixture of
the two resins is employed.
Deionized water Water that has had all dissolved ionic constituents removed. Cation and anion exchange
resins, when properly used together, will deionize water.
Demineralization See Deionization.
Density Weight of an ion exchange material, usually expressed as wet g/L or lb/ft 3 .
Desalination Removal of dissolved salts from a solution.
Diffusion Process whereby ions, atoms, and molecules move in a mix. The movement is random,
with the net effect being movement from a higher concentration zone to a lower
concentration zone until the zones have equalized.
Dissociation Process of ionization of an electrolyte or salt upon being dissolved in water, forming
cations and anions.
Distributor Piping inside an ion exchange vessel that evenly distributes flow across the resin bed.
Divinylbenzene Difunctional monomer used to crosslink polymers.
DOWEX resins Ion exchange resins used for treatment of water and other liquids. A trademark of The
Dow Chemical Company.
Double pass Process by which a stream is treated twice in series by ion exchange resins. Normally a
cation exchange resin and anion exchange resin are followed by a mixed bed or another
cation exchange resin and anion exchange resin step.
Downflow Operation of an ion exchange column in which the regenerant enters the top of the ion
exchange column and is withdrawn from the bottom. This is the conventional direction of
water flow in a co-current ion exchange column.
Dry weight capacity Amount of exchange capacity present in a unit weight of dried resin.
Eductor Device that draws a solution into the water stream by using a flow of water to create a
vacuum.
Effective size Particle size expressed in millimeters equal to the 90% retention size determined from a
particle size analysis.
Efficiency Measure of the quantity of regenerant required to remove a chemical equivalent weight
of contaminant in the influent water. For a sodium softener, this is usually expressed as
pounds of salt per kilograin or kg salt per equivalent of hardness removed.
Effluent The solution that emerges from an ion exchange column or vessel.
Eluate The solution resulting from an elution process.
Elution The stripping of sorbed ions from an ion exchange resin by passing solutions containing
other ions in relatively high concentrations through the resin column.
Exchange sites The reactive groups on an ion exchange resin.
Exchanger bed Ion exchange resin contained in a suitable vessel and supported by material, such as
grated gravel, screen-wrapped pipe, or perforated plate, which also acts as a liquid
distribution system.
Exhaustion Step in an ion exchange cycle in which the undesirable ions are removed from the liquid
being processed. When the supply of ions on the ion exchange resin that are being
exchanged for the ions in the liquid being processed is almost depleted, the resin is said
to be exhausted.
DOWEX Ion Exchange Resins 11 Water Conditioning Manual