What is meant by a Cation Exchange? First let us try to explain what the word ‘cation’ means.A cation [cat-iron] is simply the term for an ‘ion’ that has a positive electrical charge (the ‘cat’ part).

What is an ion and cation?

An ion is an atom or a group of atoms (called molecules or particles) that have lost one or more electrons giving them a positive electrical charge. An ion with a positive charge is called a ‘cation’ and an ion with a negative charged is called a ‘anion’. As all cations ‘need’ to become neutral as quickly as possible they will attract, or be attracted to, any particles or particles with a negative charge. Most catIons are usually found in solutions.

The atoms and molecules of most heavy metals that are found in the body are the result of molecular chains of inorganic compounds that have been broken down by the intake of many substances such as preservatives, smoking, petroleum processed products and vapours, drugs, alcohol, pesticides, paints, cleaning fluids and other forms of chemical pollution. As these long chained molecules are broken down within the body they each end up with a positive charge and become cations and/or free radicals which are highly reactive.

The fact that the zeolites were formed from alkaline salts has imparted them with their natural negative charge. The zeolite’s natural negative charge can be measured and expressed as a number which is the total negative charge of that zeolite. The capacity of zeolite to absorb and hold different cations is called its ‘cation exchange capacity’ or CEC. The term ‘cation exchange’ refers to the unique ability of zeolites to exchange one cation for another.

Each deposit of zeolite has its own different CEC that is peculiar to that particular deposit.The natural CEC for the zeolite used by Natural Extracts is 147. This is a very high value when compared to most overseas and some other Australian zeolites.

The higher the CEC, the stronger the attraction of a zeolite to pull in the cations and the greater the ability of the zeolite to hold on to those cations it already has within it. The more cations and other positively charged molecules that can be held in the zeolite’s cages the more effective the zeolite. A zeolite will continue to attract and hold cations until the positive charge of the cations equals the CEC of the zeolite. At this point the zeolite will become electrochemically neutral and will not absorb any more cations.

However not all cations have the same strength of charge. The cations of most heavy metals are denser and have higher positive charges than other non-metallic elements. The strength of the charge is often shown in equations and scientific papers as a + superscript next to the symbol for the element. For example, the cations of some heavy metals are aluminium [Al+], lead [Pb2+], mercury [Hg2+],nickel [Ni2+],copper [Cu2+], iron [Fe3+], zinc [Zn2+], chromium [Cr3+] compared with larger but lighter non-metals such as sodium [Na+], potassium [K+], calcium [Ca2+] and magnesium [Mg2+].

Now why is all this technical information important?

The reason is that a zeolite’s ability to release or exchange less dense cations with lower positive charges for ones that are denser and have higher positive charges allows it to suck in some cations and release others, giving it its unique ability to purify fluids and liquids. Natural zeolites can accommodate a wide variety of cations, and many other molecules which carry a positive charge. The lighter cations Na+, K+, Ca2+, Mg2+ have a low positive charge and will be readily exchanged for the heavy metals and other inorganic compounds in any fluid or solution the zeolite is in.

This ability to preferentially adsorb certain molecules, while excluding others, has opened up a wide range of ‘molecular sieving’ applications. The term ‘molecular sieve’ refers to the particular unique property of zeolites in their ability to selectively sort molecules based primarily on their size and electrochemical charge. Sometimes it is simply a matter of the size and shape of the cages that control the access into the zeolite. In other cases different types of molecules enter the zeolite, but some diffuse through its channels more quickly, leaving others stuck behind, as in the purification of para-xylene by a zeolite called silicalite. Para-xylene is an aromatic hydrocarbon used to make an acid used in the manufacture of polyester and as a solvent used in the printing, rubber and leather industries.

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