ION exchange Flashcards
What is the primary function of an ion exchange system?
Exchanges undesirable ions with more desirable ones.
What materials are commonly used for ion exchange resin beads?
Polymer resin beads (polystyrene or acrylic) or naturally occurring zeolites.
What is the typical diameter range of resin beads used in ion exchange systems?
Between 0.5 mm and 1 mm.
What happens to undesirable ions in the water during ion exchange?
They are exchanged with desirable ions attached to the functional groups on the resin beads.
What are exchange ions?
Desirable ions that are exchanged during the ion exchange process.
What is the purpose of regenerating resin beads?
To flush the beads with a strong solution of desirable ions after they are saturated.
Which solutions are commonly used for regenerating resin beads?
Brine (sodium or potassium chloride), sodium hydroxide, or strong acids (hydrochloric or sulfuric acid).
What is the effect of using water containing ions that the resin is designed to remove during regeneration?
It reduces the effectiveness of the regeneration.
What are the two directions in which units can be regenerated?
In the direction of flow used during operation (service) or in the opposite direction (counter flow).
True or False: Counter flow regeneration requires less costly equipment than service flow regeneration.
False.
What is used to monitor the effectiveness of an ion exchange unit?
The conductivity of the water produced.
List the four basic types of ion exchange resin used in water treatment.
- Weakly acidic cation
- Strongly acidic cation
- Weakly basic anion
- Strongly basic anion
According to the Bronsted-Lowry theory, what defines an acid?
A proton (H+ ion) donor.
According to the Bronsted-Lowry theory, what defines a base?
A proton (H+ ion) acceptor.
What occurs when an acid (HA) dissolves in water?
HA donates a proton to water, forming H3O+ and A-.
What are conjugate pairs in acid-base reactions?
Acid-base pairs that can donate and accept protons, respectively.
What types of cations do weakly acidic cation resins remove?
Cations associated with weak acids (e.g., carbonic and silicic acid).
What types of cations do strongly acidic cation resins remove?
Cations associated with strong acids (sulfuric, nitric, and hydrochloric).
What is a notable characteristic of strongly acidic cation resins?
They tend to remove all cations.
What do weakly basic anion resins remove?
Anions associated with strong acids but do not remove weak acids (SiO2 and CO2).
What is the main disadvantage of strongly basic anion resins?
They require strong sodium hydroxide for regeneration and have a relatively short resin life.
Fill in the blank: Weakly acidic cation resins are prone to _______.
calcium sulphate fouling.
True or False: Strongly acidic cation resins are sensitive to chlorine oxidation.
True.
What is a common issue faced during the regeneration of H+ exchange ion resins?
They can involve strong acids (HCl and H2SO4) which are hazardous to store and handle.
What is the typical resin life for strongly basic anion resins?
2-5 years.
What is the effect of thermal shock on strongly acidic cation resins?
They are sensitive to thermal shock.
What type of fouling are weakly basic anion resins relatively resistant to?
Organic fouling.
