The name bentonite derives from large deposits of clay mineral associated with Bentonite shale at Rock River, Montana USA. Some 85% of bentonite consists of forms of aluminium silicate known as montmorillonite which was identified in 1847 at Montmorillon France. Calcium montmorillonite is readily leached with mineral acid increasing its adsorption, surface area and catalytic activity.
Fuller’s earth deposits are formed by the accumulation of volcanic ash in sea water. Over a long geological time period this forms stable smectite clay which is found close to the surface in sedimentary basins. This way the unique properties so formed by due geological process preserve the unique properties of the Fuller’s earth. No deep mined Fuller’s earth is seen since the condition encountered with progressive increase in depth alters the clay minerals present, producing clay with no required useful properties.
The origin of Fuller’s earth dates back hundreds of years when the raw clay was used for cleaning woollen fleeces and woollen cloths, a process known as “fulling”. From approximately the year 1900 Fuller’s earth uses were expanded to include applications as diverse as bonding agents for foundry clays, carriers for pesticide and herbicides, drilling mud used in civil engineering projects, edible oil and fat refining, an essential ingredient in the manufacture of carbonless copying paper (NCR), and even utilised in the cosmetics industry. Fuller’s earth raw clay is always modified, depending on the required end product. When production of activated bleaching earth is required then the raw clay is activated or leached with mineral acid, washed, dried and milled, and sold for the refining of edible oils and fats and mineral oils in the petrochemical industry. Calcium smectite is the main component of Fuller’s earth and has a unique number of properties, which include a high cation-exchange capacity with a large active surface area. It is none hazardous and utilised throughout the world.
The activated bleaching earth supplied by AMC (UK) Ltd is made from sedimentary clay known as a smectite. Smectite clays are the main constituent of Fuller’s earth. The most common of the smectite clay is the clay mineral montmorillonite, which has a high Cation-exchange capacity (CEC). The main constituent of the smectite clay is calcium smectite, from which the activated bleaching clay is derived. The high quality and consistency of the activated clay supplied is in no small part due to the high purity of the calcium montmorillonite in the raw clay. Typically the raw clay comprises 95 % calcium montmorillonite; with remaining minerals accounting for some 5% and a common impurity is quartz. Globally speaking, bentonite is a commonly used term to describe smectite enriched clays, which can occur as the calcium (Ca) or sodium (Na) smectite forms. The calcium smectite or calcium montmorillonite is non-swelling clay capable of achieving high levels acid-activation and is utilised globally in the refining of edible oils and fats and petrochemical mineral oil processing. Sodium bentonite is used in the foundry business may be modified into organo clays for a host of alternative applications.