Montmorillonite

The montmorillonite is a Minéral composed of Silicate of Aluminum and Magnésium hydrated, formula (Na, Ca) 0,3 (Al, Mg) 2Si4O10 (OH) 2.nH2O, and pertaining to the group of the Smectite of the family of the Phyllosilicate S.

Data

  • external Surface: 80 m ² per gram
  • Surface inerne: 720 m ² per gram
  • Are an entire surface of exchange of 800 m ² per gram (very reactive)
  • 10 layers piled up form an elementary crystallite
  • Type of assembly: in house of cards
  • interfoliaceous Space (between the layers) open with a long distance (variable) between the layers
  • isomorphic Substitutions possible

Layer

The montmorillionite is a clay of the type 2/1. That means that layer of montmorillionite is made of three layers:
  • an octahedral layer; Al (OH-) _5O: 7 atoms for 6 tops + Aluminimum in the center. The OH- and the oxygen being divided between the different octahedral ones which compose the layer.
  • and two layers tetrahedral which recover each with dimensions the octahedral one; SiO_4: 5 atoms for 4 tops + the Silica in the medium. Oxygens being divided between the various tetrahedrons which compose the layer.

Layers

The name comes from the locality Montmorillon, in the Vienna. Montmorillonite layers exist with the USA (Utah, Wyoming, Upon, Texas). Montmorillonite with kaolinite are very widespread clays on the surface of the sphere.

This mineral is present also on others Planet S, in particular Mars.

Properties

One of the most remarkable properties of montmorillonites is their capacity of swelling resulting from the presence of water in space between the layers. A montmorillonite put in solution gives a stable colloidal solution very easily. Their properties of plasticity and impermeability are also very required in industry.

Contrary, these capacities of swelling pose problems in the field of the Géotechnique, by imposing sometimes important displacements on the foundations with the liking of the variations of moisture of the basement.

Use

In Pharmacy, this substance is used against the Gastro-entérite.

Agriculture

Montmorillonite is the constituent main thing of the inflating Argile S, which have the property to create broad slits of desiccation in period of dryness. These slits can be deep one meter and ensure a work of in-depth ground. Thus marked seasons make it possible to carry out a tillage only before sowing.

These characteristics come from the fitting of its layers in a context of adequate pH (presence of Ion Calcium which bridge the layers between-them).

In agriculture, these characteristics are appreciated by the increase in useful reserves which they bring on the cultivated ground.

Nuclear power

Montmorillonites are one of materials under consideration with the granite and salt like materials of coating and containment of the radioactive waste with high activity. In France, the possibility of an in-depth and reversible storage with fact of privileging clays like principal choice. The underground laboratory built by the ANDRA and located with Bure is located in an argillaceous layer at 500 m of depth.

Other names

See too

External bonds

  • the chapter “ clay and medicine ” of the following site describes the role of montmorillonite against gastro-enteritis.
  • Montmorillonite over Mars Iron-montmorillonite: spectral analog Martian soil
  • BRGM has off set up a gate of information on the problems of withdrawal-swelling of the grounds.

Random links:Phaenomys | Costa LED Ground | Leigneux | Memories (film, 1995) | Turtle-dove with white wings | Équilibrage_de_la_charge_(calcul)