Zeolite Addendum

1
Zeolite Addendum

• Additional material for Class 11

2
Handouts

• Zeolite text or handbook, origin unknown
• Preprint Comparison of Materials for Making
  Hydroceramic Waste Forms, D. D. Siemer, M. W.
  Grutzeck, and B. E. Scheetz
• Why Hydroceramic Solidification Makes More Sense
  Than Vitrification For Ineel High Level Waste, D.
  D. Siemer
• Zeolite Review Brief commentary on zeolites as
  a HLW form, G. Beitel
• Zeolite Materials, pdf file from Penn State
• Paper on manufacturing glass from Titanite
  zeolite
• 1972 NAS Evaluation of SRP HLW, Interesting
  Historical Summary

3
Zeolites

• The zeolites are a popular group of minerals for
  collectors and an important group of minerals for
  industrial and other purposes. They combine
  rarity, beauty, complexity and unique crystal
  habits. Typically forming in the cavities, or
  vesicles, of volcanic rocks, zeolites are the
  result of very low grade metamorphism. Some form
  from just subtle amounts of heat and pressure and
  can just barely be called metamorphic while
  others are found in obviously metamorphic
  regimes. Zeolite crystals have been grown on
  board the space shuttle and are undergoing
  extensive research into their formation and
  unique properties.
• The zeolites are framework silicates consisting
  of interlocking tetrahedrons of SiO4 and AlO4.
  In order to be a zeolite the ratio (Si Al)/O
  must equal 1/2. The alumino-silicate structure
  is negatively charged and attracts the positive
  cations that reside within. Unlike most other
  tectosilicates, zeolites have large vacant spaces
  or cages in their structures that allow space for
  large cations such as sodium, potassium, barium
  and calcium and even relatively large molecules
  and cation groups such as water, ammonia,
  carbonate ions and nitrate ions. In the more
  useful zeolites, the spaces are interconnected
  and form long wide channels of varying sizes
  depending on the mineral. These channels allow
  the easy movement of the resident ions and
  molecules into and out of the structure.
  Zeolites are characterized by their ability to
  lose and absorb water without damage to their
  crystal structures. The large channels explain
  the consistent low specific gravity of these
  minerals.

4
Minerals

• Scolecite CaAl2Si3O10-3H2O, Hydrated calcium
  aluminum silicate
• ChabaziteCaAl2Si4O12 - 6H2O, Hydrated calcium
  aluminum silicate
• Laumonite Ca(4) Al(8) Si(16) O(48).16H2O
  Hydrated calcium aluminum silicate
• Analcime NaAlSi2O6-H2O, Hydrated sodium aluminum
  silicate
• Natrolite Na2Al2Si3O10-2H2O, Hydrated sodium
  aluminum silicate
• Stilbite NaCa2Al5Si13O36 -14H2O, Hydrated sodium
  calcium aluminum silicate
• Heulandite (Ca, Na)2 - 3Al3(Al, Si)2Si13O36 -
  12H2O, Hydrated calcium sodium aluminum silicate
• Mesolite Na2Ca2Al6Si9O30 - 8H2O, Hydrated sodium
  calcium aluminum silicate
• Phillipsite KCaAl3Si5O16 - 6H2O, Hydrated
  potassium calcium aluminum silicate.
• Harmotome BaAl2Si6O16 - 6H2O, Hydrated barium
  aluminum silicate
• etc.

5
Observations

• All zeolites have waters of hydration
• If the water is driven off, the zeolite is
  transformed to a Feldspar (a German word for
  field rock, i.e., a common rock
• The most common feldspar is NaAlSi3O8, Sodium
  aluminum silicate
• If a water is transformed to a hydroxl, OH-,
  probably with the loss of sodium also, the
  zeolite transforms to a clay, for example,
• Kaolinite Al2Si2O5(OH)4 Aluminum Silicate
  Hydroxide

6
Observations Continued

• It is this interchange and relationship to long
  term natural analogues that make zeolites
  interesting for waste management
• If they pick up water they behave like clays
  which have a strong attraction for metal ions
• If they lose water they become more feldspathoid
  (rock like)
• If they just hold the water, as zeolites they are
  geologically stable and a powerful ion exchange
  media

7
Cl and Nitrate

• Cancrinite and Sodalite
• Close relatives of zeolites both contain
  chlorine (Cl-) Cancrinite is hydrated and
  sodalite contains no H2O or OH-
• There are no minerals which contain NO3- with the
  sole exception of NaNO3 and KNO3

8
Synthesis of Zeolite (paper handout)

• This is a difficult paper to read, but provides
  the details of past attempts in the non-waste
  world to synthesize zeolites.
• Hundreds of zeolites have been synthesized
• Key points
• Temperatures less than 500C, most often less than
  200C, some as low as 100C
• Typical ingredients
• NaOH
• Silica Gel
• Diatomite
• Sodium Silicate
• Clays and glass
• Water as steam
• Both Calcium and Sodium based zeolites have been
  prepared