DOWEX Ion Exchange Resins WATER CONDITIONING MANUAL

Ion Exchange Resin Operational Information
9.6.4 Osmotic Shock
The alternative exposure of resins to high and low concentrations of electrolytes can cause resin bead
cracking and splitting due to the alternate contraction and expansion of the bead. Over time, there may be
significant reduction in particle size and an increase in resin fines, causing increased pressure drop
across the resin bed during system operation and subsequent resin losses during backwash and
regeneration. The resistance that a particular ion exchange resin has to osmotic shock can be determined
by subjecting the resin to repeated cycles of high and low concentrations of electrolytes, such as NaOH
and H2SO4.
Ion exchange resin particle size is an important factor related to osmotic shock. Smaller beads,
��������������������������������������������������������������������à ������������������
to breakage than larger particles.
9.6.5 Mechanical Attrition
The physical stability of most currently used ion exchange resins is adequate to prevent attrition losses in
column operations. Bead breakage due to mechanical attrition can occur when the resin is subjected to
unusual mechanical forces, such as a crushing valve, a pump impeller, or an abrasive action during the
movement of resin particles from one vessel to another. The broken beads will maintain the same
operating capacity as whole perfect beads, but they are more prone to fluidization during backwash, and
may be lost. In addition, the small fragments will fill the void spaces between the whole resin beads,
resulting in increased pressure drop across the bed. Large beads are more subject to mechanical attrition
than smaller ones.
9.6.6 Radiation
Since ion exchange resins are organic polymers, they can be affected by radiation. Generally, cation
exchange resins are adequately stable for almost all reasonable applications involving radioactivity.
Radiation damage shows up as a de-crosslinking of the resin. Anion exchange resins are less stable
although generally adequate for use in radiation fields.
9.7 Useful Life Remaining on Ion Exchange Resin
The degradation mechanism for cation resins is de-crosslinking of the polymer matrix, leading to an
increase in swell and water retention capacity. The approximate useful life of cation exchange resins may
therefore be evaluated by comparing the water retention capacity to the original resin. Anion resins
degrade by loss of total capacity and strong base (salt splitting) capacity, so the useful life can be
assessed by comparison of the remaining salt-splitting capacity with that of the original resin. Figure 24
and Figure 25 show these relationships.
DOWEX Ion Exchange Resins 55 Water Conditioning Manual