Acid
A substance which releases hydrogen ions when dissolved in water. Most
acids will dissolve the common metals and will react with a base to
form a neutral salt and water.
Acrylic Resin
Resin that is made with an acrylic polymer instead of a styrene polymer.
Acrylic resins can be activated with weakly acidic, weakly basic, or
strongly basic exchange groups.
Anion Resin
A positively charged resin bead that exchanges negatively charged ions
in the water. (See ProSelect™)
Bed Expansion
The increase in volume of a bed of ion exchange resin or filter media
during upflow operations such as backwashing, due to lifting and separation
of bed materials.
Capacity
The amount of an element that resin will pick up before it needs to
be regenerated. With softening resin, this usually applies to hardness
measured in kilograms per cubic foot of resin. Standard cation resins,
once in service, will generally remove 30,000 kilograms of hardness
after it is regenerated with salt (sodium chloride). With nitrate removal,
resin calculations can be done to estimate the ppm (parts per million)
of nitrate removal before the resin bed is exhausted and another regeneration
of salt is needed. Capacity is measured in many different ways and other
elements can run interference on a resin’s capacity.
Cation Resin
A negatively charged resin bead that exchanges positively charged ions
in the water. Cation resin is most often used for removing calcium and
magnesium (hardness) from water. (See ProSoft™)
Contact Time
The time that brine or other regenerant at the
proper strength is moving through the resin bed.
Crosslink
A chemical bridge that connects the polymer chains of a resin bead;
the glue that holds the resin beads together. Generally, the higher
the crosslink, the tougher the resin. For cation resins, higher crosslinking
also means more resistance to chlorinated water.
DVB
Stands for "Divinylbenzene." Divinylbenzene is the chemical
most commonly used to cross link polymers that are used to make ion
exchange resins.
Dyed Resin
Resin that is colored with a dye that is pH sensitive and changes color
as the pH of the resin changes.
Effective Size
A measure of the size of particles of an ion exchange resin or filter
media, defined as the diameter of a specific particle in a bed, batch
or lot which has ten percent smaller and 90 percent larger particles.
Elution
The stripping of ions from an ion exchange material by other ions, either
because of greater affinity or because of much higher concentration.
Fouling
The process in which undesirable foreign matter accumulates in a bed
of filter media, ion exchange resin or membrane process, clogging pores
and coating surfaces, thus inhibiting the proper operation of the system.
This can be due to the presence of suspended solids, precipitated salts
or biological growth, and can cause a decrease in both the amount of
water produced and the quality of water.
Freeboard
The vertical distance between the top of a resin bed or filter media
and the overflow or collector for backwash water. This may be expressed
either as a linear distance or a percentage of bed depth.
Gel Resin
Resins that do not have discrete pores and are translucent in appearance.
Gel resins generally have higher capacity than macroporous resins.
Ionic Form
Refers to the particular type of ion that is exchanged onto an ion exchange
resin. (e.g. - The ionic form of ProSelect™ Tannin is Cl (chloride)
and the regenerant used is salt (sodium chloride). This means that the
chloride side of the salt is the exchanged ion.
Leakage
The presence of a consistent concentration of ions in the effluent of
an ion exchange system, due to incomplete removal of the ions.
Macroporous Resins
Resins that have discrete pores and are opaque in appearance. Macroporous
resins are generally stronger than gel resins.
Mixed Bed
The blending of cation and anion resins into a single bed. These resins
are mostly used in D.I. or specialty applications. By mixing and matching
different resins and ratios, different results can be accomplished.
Operating Capacity
The quantity of ions that can be exchanged by a resin before leakage
bleed-through of ions occurs. This term also refers to resin in service,
rather than resin fresh out of the bag.
ProSelect™
At SWT, we believe it is the best anion resin you can buy.
ProSoft™
At SWT, we believe it is the best cation resin you can buy.
Regeneration
This process includes the backwash, brine, and fresh water rinse steps
necessary to prepare a water softener ion exchange bed for service after
exhaustion.
Selectivity (Relative Affinity)
A quantitative measure of a resin’s preference for various ions
at equilibrium between the resin and water. In general, an ion with
greater selectivity will be removed preferentially to an ion with lower
selectivity (as in the case of "nitrate selective" resins).
Strong Base
Anion resins that are capable of splitting salts and can therefore operate
in an alkaline environment and can remove weakly ionized substances,
such as carbon dioxide and silica.
Total Capacity
The maximum quantity of ions that a resin is capable of exchanging.
Total Dissolved Solids (TDS)
The quantity of all the dissolved minerals in water.
Type 1
Strong base anion resins that are activated with trimethylamine. These
resins are relatively more stable and produce higher water quantity,
but have lower capacity and give off a "fishy" odor when used
in the hydroxide form.
Type 2
Strong base anion resins that are activated with dimethylethanolamine.
These resins have a higher capacity and are more easily regenerated,
but do not produce as high of a water quality and generally have a shorter
life.
Weak Base
Anion resins that can only function under acidic conditions, can only
exchange for strong acids, and can not remove weakly ionized substances.
Zeolite
A class of inorganic ion exchange materials that are based on aluminosilicate
chemistry (e.g. — clay based compounds). Zeolites have lower capacities
than ion exchange resins, but are more selective for certain ions.
