Bentonite and Fuller's Earth
Bentonite and Fuller's Earth are the two important naturally occurring clays of great commercial importance possessing inherent bleaching properties. They are, therefore commonly called bleaching clays. They fall mainly under montmorillonite group containing a varying amount of attapulgite. The clay minerals of montmorillonite and attapulgite groups are distinguished by their adsoption characteristics. The chemical composition of these clays is similar to that of other common clays and it is rarely that these clays can be identified by chemical analysis. The natural activity in the clay is determined by actual trials. The other important property of the montmorillonite group of minerals is possession of exchangeable ions.
Bentonite Properties
In the early years, all naturally occurring activated clays having good bleaching properties were called fuller's earths. The word fuller's earth has been named after the practise of fulling or cleaning the grease and stains from wool and cloth.
The essential difference between bentonite and fuller's earth is in their modes of occurrence and other physical properties. Bentonite is regarded to have been formed by the alteration of volcanic ash deposits, mostly in upper Cretaceous formations. Fuller's earth represent a shaly facie of Tertiary rock. Two types of bentonite are generally identified. One is called the swelling type or sodium bentonite, which has single water layer particles containing Na+ as the exchangeable ion. The other has double water layer particles with Ca++ as the exchangeable ion. It is called calcium bentonite or non-swelling type. Na+ or Ca++ is exchanged by Mg++ or Fe++. A third type of montmorillonite has been identified with zero water layer particles and is probably electrostatically neutral. Calcium bentonite is usually referred to as fuller's earth by a number of authorities because chemically and also in physical properties it is identical to calcium-montmorillonite.
Bentonites having low iron content, have been found to be good catalytic agents in petroleum refining. The bentonites having Ca and / or Mg as exchangeable ions are good decolourizers. Bentonites can absorb water to a greater extent than ordinary plastic clays. Fuller's earth, on the other hand, is non-plastic or semi-plastic in character. It has a foliated structure. Dry or dehydrated fuller's earth adheres strongly to the tongue. The absorption of water in sodium bentonite proceeds with a considerable increase in volume (as much as 14 times its original volume) creating an excellent gel and viscous material which is invaluable for the preparation of drilling muds and in grouting of dams, wells etc. Sodium bentonite has an excellent thixotropic property, i.e. the gel becoming stiff on standing and reverting to fluidity when shaken. The swelling type bentonite when dispersed in water, separates into suspendible flakes which are all finer than 0.5 micron. Calcium bentonite yields about 35% finer than 0.5 micron. Calcium bentonite yields about 35% finer than 0.5 microns. The difference in bentonite and other clays lies in lattice structure. The sheet of atoms in bentonite are much thinner and more easily separable in water. That is why bentonite occupies more surface area than other clays. This property is known as dispersibility, which is unique to swelling type of bentonite.
Bentonite Procedure
Weigh accurately about 200 gm. of the alkali refined ground oil in a round-bottom flask. Immerse the flask in a water-bath maintained at 90º to 95ºC, slowly bubble carbon dioxide gas through the oil. When the temperature of the oil has reached 90ºC momentarily remove the cork and introduce 2.0 gm. of the material. Start the stirrer and adjust its speed to about 350 rpm. The bottom end of the stirrer should be adjusted to a level at which intimate mixing is ensured. Maintain the temperature at 90ºC for 20 minutes and then stop stirring. Remove the flask from the water-bath, allow the oil to cool in the atmosphere of carbon dioxide and filter the oil through filter paper Watman No. 1. Determine oil in the glass cell using a Lovibond tintometer.
In order to obtain a better insight into the performance of the materials, it is recommended that the procedure mentioned be repeated with at least three additional quantities of the material, say, 1.0 gm., 3.0 gm., and 4.0 gm., and the values for decolourizing power plotted against the percentage of material added.
By agreement between the purchaser and the seller, any vegetable oil, other than alkali-refined groundnut oil of agreed colour intensity, may be used for this test. In such a case, it may also be necessary to use a glass cell of some other thickness and also to express the colour reading in terms of factor other than.
Clay, generally of 200 mesh is used in the contact process and 60 to 80 mesh in the percolation process. A bleaching clay is evaluated for three percolation process. A bleaching clay is evaluated for three properties: Bleaching efficiency, Settling efficiency.
Bentonite Crusher & Bentonite grinding mill
Bentonite crusher is a type of stone crushers that is used to crush Bentonite. Bentonite is the raw materials for construction, road, bridge and railway buiding and small gravel are also important for the manufacture of concrete. Bentonite has all kinds of shape and size. So it is not suitable for buiding material. Bentonite crusher can crush native rock into all kinds of size to create Bentonite for use in the concrete for the dam and other buiding. Bentonite crusher is the esssential mining and construction machine. And you can grind the bentonite into powder with bentonite grinding mill.
SBM bentonite crusher Machinery manufactures a full line of crusher and grinding equipment for use in processing quarried bentonite. SBM Machinery specializes in designing and manufacturing of bentonite crusher for our clients. You can talk to the 24-hour customer service for relevant information.
