Questions about ion exchange

Certification Action Line features questions and answers typical of those appearing in Water Quality Association (WQA) certification examinations. Some answers may not satisfy everyone or every condition.

Answers to these questions appear at www.watertechonline.com/certification-action-line.

1. The word “macroreticular” in describing ion exchange resins means:
      a) very intricate
      b) more polystyrene chains
      c) large pores
      d) all of the above

2. Macroporous resins are sometimes called gelular resins.
      a) True
      b) False

3. For many ion exchange applications, a resin bead size in the range of 20 to 50 mesh (0.84 to 0.297 millimeters in diameter) is chosen because this size:
      a) exhibits an acceptable amount of bed expansion during back wash (to classify the bed and to remove fine particles and dirt from the resin bed).
      b) exhibits a reasonably low pressure drop in a 30-inch deep packed bed.
      c) maintains a large surface area of the ion exchange beads and thereby reasonably fast ion exchange kinetics to accommodate higher flow rates per unit volume of resin.
      d) all of the above.

4., 5., 6. & 7. Resin beads sometimes are built with monomers that already contain ion exchange functional groups, but mostly they have to be further treated or reacted to add the ion exchange functional groups to the resin. Match the following type of resin with its respective permanently affixed ion exchange functional group.

8. What is the maximum amount of water that can be entrained in one cubic foot of resin in a packed bed?
      a) 7.5 gallons
      b) one cubic foot
      c) three gallons
      d) one gallon

9. What minimum straight sidewall height would be necessary to accommodate a resin bed depth of 30 inches, six inches of resin underbedding and 40 percent bed expansion.
      a) 48 inches
      b) 54 inches
      c) 40 inches
      d) 45 inches

10. In addition to pressure drop from water flow through the resin bed depth, the next most significant source of water pressure loss through a typical water softener is:
      a) the valve
      b) the resin interface with the distributor
      c) the riser tube
      d) the inlet distributor