It is well known that a variety of naturally occurring minerals, such as clay minerals that are commonly present at the bottom of lakes, ponds, and other surface water bodies possess varying degrees of net electrical charges, either negative or positive. By virtue of these net charges, they will attract oppositely charged molecules and bond together to form a different chemical molecule (ionic bond). Some of these chemical molecules can possess a very weak or partial ionic bond, and others can possess a very strong ionic bond.
The strength of the ionic bond can be calculated using the Born-Landé equation as the sum of the electrostatic potential energy, calculated by summing interactions between cations and anions, and a short range repulsive potential energy term. The electrostatic potential (Electronegativity) can be expressed in terms of the inter-ionic separation and a constant (Madelung constant) that takes account of the geometry of the crystal.
The strength of the bond between a sorbent (e.g., clay mineral) and a sorbate (e.g., phosphate) depends on a variety of factors. These factors include the structural configuration or geometric shape, including surface area of the solid phase and the zero point of charge of the solid phase (which is pH dependent) involved. In general, the larger the surface area, coupled with the strength of the electrical charge, the more it will attract and cause an ionic bond to an oppositely charged and suspended molecule. The stronger the opposite electrostatic charges are, the stronger the ionic bond. In the case of weak (or partial) ionic bonds, the more easily they can be broken apart by competing dissolved ions or a change in the aqueous phase pH. Sorption characterized by a strong ionic bond typically requires extreme chemical changes in the water, such as a very strong pH level change, which rarely occurs naturally.
TPX™ was developed with these considerations in mind to optimize its sorption characteristics with the phosphate anion. As a result, TPX™ has the strongest binding characteristics at ambient pH levels of any sorbent we have tested – including alum and various iron salts.
Technically speaking, TPX™ crystals are very similar to the chemistry of sand found in the sediment of healthy surface water bodies. Most sedimentary sand consists primarily of calcium or silica. Coral sand is composed primarily of calcium and most inland non-tropical sediment sand is primarily composed of silica. However, TPX™ crystals are engineered for the optimal shape, size, purity and chemical ionic charges to create the strongest attraction and chemical electrostatic charge possible and permanently remove excess P from the water column. Additionally, TPX™’s chemical-electrical reaction, when settling through the water column, creates a wide attraction field around our crystals. Adsorption rates for TPX™ crystals have been proven to achieve greater than 100% P adsorption (mass of P to the mass of TPX™), which is significantly greater than any other adsorbent known today. We believe that higher adsorption rates are difficult to achieve using any other chemistry. TPX™ is the only media that is inert in a typical surface water body environment and does not produce muck or other sticky, flocculent material. Additionally, it does not induce aquatic toxicity or create any of the other adverse side effects that competing nutrient removing technologies exhibit.