Carolyn Rulli

Chemistry 503

Molecule Report

 

Sodium Zeolite

 

          Sodium Zeolite is a a white powdery substance with a cubic crystal structure.  It has a density of 0.40 to 0.48 g/ml. In water, it hydrolyzes to give a basic pH.  A 1% dispersion of sodium zeolite in water has a pH range of 10.1 to 11.4.  Because Sodium Zeolite is a mineral, its chemical composition can vary somewhat.  Average chemical composition of sodium zeolite is reported as Sodium Oxide - 17%, Aluminum Oxide -  28%, Silicon dioxide – 33% and water – 22%.1  The formula of sodium zeolite may be represented by NaAlSi2O6-H2O.  Another name for this substance is hydrated aluminum silicate.  The structure of sodium zeolite is an isometric trapezohedron.  This structure contains a relatively large central open area will allows large ions or other molecules to move through or reside within its framework.  As a result, sodium zeolite can function as a chemical sieve.  Deposits of this mineral can be found in New Jersey. 2

          One of the most important uses for this mineral is in detergents.  Sodium Zeolite replaces sodium tripolyphosphate in detergents as a water softener.  (Phosphates in detergents were responsible for the increased algae growth in the waste-water.)  Sodium Zeolite acts as an ion exchange medium.  Calcium cations in water are exchanged for the sodium ions of the zeolite.  In addition to water softening, sodium zeolite has been used as a catalyst in the cracking of petroleum, as a drying agent, and as an absorbant.3   This material has also been used as a stabilizing agent which, when added to PVC, can prevent the degradation of water pipes.4

          Sodium Zeolite can be extracted from detergents.  Since zeolites are relatively insoluble in water, they can be separated from an aqueous solution of detergent by filtering.  Heating the residue will drive off any waters of hydration.  The zeolite extract can then be tested for properties of water softening, dessicant ability, ion exchange and its effect as a dehydration catalyst in a procedure outlined in the Journal of Chemical education, Vol. 74, No. 5, May 1997, p.569-570.5

                Sodium Zeolite is a member of a class of compounds commonly referred to as zeolites.  Generally, zeolites have a general formula [(SiO2)(AlO2)x]M x/n n+ · w H2O. M is a cation with positive charge equal to n.  It is usually a group I or II metal ion.  The silicon and aluminum oxide part of the substance provide the framework of interconnected tetrahedral structures.  The metal ions inhabit the inner open area of the compound.  These open areas can be connected and act as channels.  The diameter of the pores in most zeolites ranges from 0.26 to 0.74 nm.  The actual pore size for many zeolites is known and can be selectively used as a specific molecular sieve.6   Although there are many types of natural zeolites, some are synthesized in the laboratory for either commercial or research use.  Several million tons of zeolites are used globally each year.7 

Zeolites can be used to catalytically crack petrochemicals.  Non-branched alkanes can be cracked to form branched chains, increasing the octane rating for the fuel.    Zeolite Hydrogen Y can be used to catalyze the ester formation from an organic acid and an alcohol.  This reaction is classically catalyzed with concentrated sulfuric acid.  Replacement of the sulfuric acid, results in a safer procedure.  The zeolite catalyst, insoluble in water, can be reclaimed at the end of the reaction and reused.8

Environmentally, zeolites are friendly chemicals.  Mentioned previously, zeolites replaced phosphates in detergents, significantly reducing water pollution globally.  Zeolites have acidic properties and can replace more toxic acids in some commercial applications..  They can also absorb harmful atmospheric gases such as CFC’s and gases from automobile exhaust.  In water treatment, zeolites can remove harmful organics as well as heavey metal ions.9

          Zeolites are uniquely able to dehydrate or rehydrate without affecting their structure.  They can also absorb gases.  Since the innerchannel is an open framework, zeolites can allow solution to flow through their structure.  Addition of zeolites to animal feed has been shown to absorb toxic materials.  Zeolites can also remove ammonia and other toxins from aquariums.  Currently, there 45 different types of natural zeolites have been identified.  Synthetic zeolites may also be prepared.  This diverse group exhibits at least 120 different structures.  It is reported that each year, more are being synthesized.10

            

References

 

1.     Advera Specialty Zeolites, Valley Forge Pa., Product Information Page, April 22, 2004.

2.      The Mineral Galleries, http://mineral.galleries.com/minerals/silicate/analcime/analcime.htm

3.     Smoot, A., Lindquist, D., Properties of Zeolite A Obtained from Powered Laundry Detergent, Journal of Chemical Education, Vol. 74, No.5, May 1997, p 569-570.

4.     The PQ Corporation Product Specification Sheet, Advera® 401/401P Hydrated Sodium Zeolite A, http://www.pqcorp.com/Products/advera401p.asp, April 20,2004.

5.     Smoot, A., Lindquist, D., Properties of Zeolite A Obtained from Powered Laundry Detergent, Journal of Chemical Education, Vol. 74, No.5, May 1997, p 569-570. 

6.     Coker, E. and Davis, P., Experiments with Zeolites at the Secondary School Level: Experience from the Netherlands, Journal of Chemical Education, Vol. 76, No. 10, October 1999, p 14171419.

7.     What are Zeolites?, http://www.bza.org/zeoliets.html, April, 20, 2004.

8.     Coker, E. and Davis, P., Experiments with Zeolites at the Secondary School Level: Experience from the Netherlands, Journal of Chemical Education, Vol. 76, No. 10, October 1999, p 14171419.

9.     What are Zeolites?, http://www.bza.org/zeoliets.html, April, 20, 2004.

10. The Mineral Gallery – The Zeolite Group, http://mineral.galleries.com/minerals/silicate/zeolites.htm, April 20, 2004.