Characteristics of Zeolite Ore

• Like any other matters, Zeolite has two major characteristics which are:

1.      a chemical composition having zeolitic water, and

2.      An excellent ion exchange capability.

Zeolitic water is unique in the composition which is hardly observed in other minerals, as dehydration occurs without changing the crystal structure under heating. This hydration behaviour enables zeolite to be used as moisture absorbent.

In addition, the dehydrated zeolite has a myriad of holes like a honeycomp and the holes have such small sizes in the order of angstroms (Symbole:Å, unit cm/100 million). Accordingly a mixture of gasses with different molecular sizes, which are chemically difficult to separate at the molecular level, can be sieved through zeolite. This is called the “molecular sieve effect.”

The Cation exchange capacity of zeolite is explained as follows:

The general chemical composition of zeolite in general is indicated by

(M²⁺,M₂₊)O.Al₂O₃.mSiO₂.nH₂O. The symbols in the parentheses at the beginning of the formula indicate exchangeable cations. Cations in zeolite are exchangeable with other cations in aqueous solutions. In chemical terms, material with a positive charge is referred to as a base. The ability to exchange bases is Base Exchange capability (or cation exchange capability), while the capacity to exchange bases is base exchange capacity (or cation exchange capacity) and is called C.E.C., the acronym for “Cation Exchange Capacity.”

Ion exchangeability allows silicon (Si) atoms located in the centre of the zeolite crystal lattice to be partially replaced with aluminium (Al) atoms, resulting in the loss of cations. Cations such as sodium (Na), Calcium (Ca) are captured in the crystal lattice to compensate for the shortage.

The function of C.E.C. is similar to that of the liver of an animal which stores nutrients. Zeolite adsorbs and stores fertilizer components (bases) such as sodium, potassium and calcium to supply the nutrients (fertilizer components) to crops in response to request.

The unit of cation exchange capacity is represented by mg equivalent (meq) per 100g of soils or zeolite rocks.

The cation capacities of clay minerals are different depending on the type of minerals. Montmorillonite is the main mineral source for bentonite which exhibits the highest C.E.C. after zeolite.

Reference:

Boiling stone (zeolite), Zeolite Dynamics, Lecture Notes.

Roskill Report (1990)

Annual Reports of Various Companies.

Nouko to Engei (Agriculture and Horticulture), September 1978.

JACT News.