The animal feed industry uses a wide range of inorganic compounds, collectively referred to as clays or toxin binders. It may be interesting to know about its emergence, widespread use, effectiveness, and other related factors.
Clay is a heavy type of soil that has unique properties. When wet, it is sticky and mushy, and when dried or heated, it hardens. In fact, the first-ever ceramic substance discovered was clay.
Clay is inherently inorganic and a product of natural mines. They are simply endowed with a variety of innate qualities by the earth, which carves them into its crust. There are approximately 90 elements in the earth’s crust, but only a few are necessary to create soil, rocks, and minerals. Some “non-silicate” minerals, such as carbonates, oxides, halides, sulphites, etc., are composed of these elements but are not the subject of the discussion here. Here we discuss the remaining 90% of the earth’s crust, which has the highest concentration of silicon.
The form of silicon that is present in the crust of the earth is silicon dioxide, usually referred to as “quartz” (SiO2). It may easily combine with other substances to create “Silicates,” which then act as adsorbents.
Silicon Dioxide bonds very easily with native minerals, aluminium & we get our next abundant constituent, the “Aluminosilicates”. Silicon dioxide (Silicates) together with Sodium & Potassium forms Sodium silicate or Potassium silicate commonly known as “Feldspar” (an important ingredient of drinking glasses & window panes). Here is the classification of Silicates & further Aluminosilicates in brief.
Silicates and Aluminosilicates
A basic silicate is a mineral containing silicon & oxygen in tetrahedral (SiO4)4- units, which are linked together in different patterns.
The formation of HSCAS
The SiO2 (or Silicate) always reacts with one or the other metal cations like Sodium, to form Sodium Silicate (Na2SiO3), with Calcium to form Calcium Silicate (Ca2SiO4), Magnesium to form Magnesium Silicate (MgSiO3), Potassium to form Potassium Silicates (K2O3Si) or Aluminium to form Aluminium silicate, commonly, Aluminosilicates. Aluminosilicates may be hydrated or anhydrous, which may occur in nature as minerals or may be synthetically produced for commercial purposes. When aluminosilicates occur with one or more cation, like sodium and calcium, we call them, Sodium Calcium Aluminosilicates, when it is hydrated, it is named Hydrated Sodium Calcium Aluminosilicates (HSCAS), sometimes they are known as hydrated Bentonites and commonly as Zeolites.
Further, the framework silicates, the 2D silicates with plate-like arrangement or phyllosilicates, and the 3D Silicates or net-like arrangement or tectosilicates (Classification I) along with metal cations are broadly used as clays for toxin binding and can be further classified as follows.
Some phyllosilicates possess coordinated positions with two of the octahedral sites occupied by metal cations are called Dioctahedral phyllosilicates and the phyllosilicates with three octahedral sites occupied by metal cations are called Trioctahedral phyllosilicates. One tetrahedral sheet for each octahedral sheet represents 1:1 Phyllosilicates and similarly, one tetrahedral sheet for two octahedral sheets represents 1:2 Phyllosilicates. These ratios represent the number of cations that the clay or phyllosilicates can acquire and are associated with the CEC value of the clay. CEC, the Cation Exchange Capacity of clay is a property, that determines its efficacy in sequestering polar toxins. CEC becomes more important when selecting the clays as a toxin binder and the extent to which they can spare the essential nutrients in animal feed. Various silicates highlighted in the classification are among the most suitable clays that are commonly used in animal feed to bind various toxins.
The nomenclature story of clays
We often come across various names that are associated with the clays, the very common being the Bentonite. Let us unravel how these names are being conferred. “Bentonite” got its name from the place, Fort Benton, in Montana state of the USA, where it was discovered. Bentonite is typically a name given to the phyllosilicate of the Smectite class that is predominantly a Montmorillonite, as classified. Bentonites are one of the first rocky formations of swelling type of clays. (Informativa E Prestazione DCASD 196/2003). Similarly, “Montmorillonite” got its name from the place, Montmorillonite, a commune in France, where it was discovered. Whereas, by classification, it is a Smectite clay which is dioctahedral in its structure. In nature, Montmorillonite occurs along with metal cations like Sodium and Calcium and is often identified as Na-Montmorillonite and Ca-Montmorillonite. Further, Saponite, a phyllosilicate of the smectite class, got its name from Latin sapon, meaning soap, because of its appearance and ability to clean. The name “Kaolinite”, a phyllosilicate, got its name after the Kao-ling, a mountain in Jiangxi Province of China, where this silicate was first identified. Kaolinite was the first sample of clays used in the manufacturing of porcelain. “Illite” a non-expanding phyllosilicate of the mica category, interestingly, got its name from the place of its origin, Illinois in the USA. We might just have categorized the clays as phyllosilicates or tectosilicates based on their structural makeup, and we might be using them as toxin binders in our practice.
The classification, simplification, and differentiation of clays based on their common names and the rationale behind their nomenclature, on the other hand, is always interesting. Together with varying degrees of expandability and cationic exchange capacity, all the clays are efficient enough to bind various toxins in animal feed electrostatically and therefore are the super engineers.
by Dr. Rajib Upadhyaya, Cargill India