Sb - Antimony

Properties

Antimony is not quite a metal, and is often referred to as a metalloid element.  It is a member of Group 15 of the Periodic Table, and is the 63rd most abundant element within the Earth’s crust. Antimony can exist in two forms: the metallic form is bright, silvery, hard, and brittle; the non-metallic form is a grey powder. Although antimony is known as a metal, it is a very poor conductor of electricity and is toxic to humans. Antimony is not attacked by dilute acids or alkalis, and is stable in air at room temperature, but it will react with oxygen if heated to form antimony trioxide, Sb2O3.  Antimony metal has a curious property: it expands when it solidifies, making it suitable for various uses.

History

Antimony and its compounds were known to the ancient world, and there are artefacts remaining from these times, such as a 5,000-year-old vase in the Louvre, which is almost pure antimony metal. Ancient Egyptian scriptures dating back to the 16th century BC mention the use of antimony sulfide (Sb2S3), and from that time onwards the black form of this pigment, which occurs naturally as the mineral stibnite, has been used as a type of mascara known as khol. The chemical symbol for antimony (Sb) was taken from the original name for the element, stibium, and its current name originated from the Greek language. Not until 1783 was the first natural occurrence of pure antimony documented. Alchemists were very intrigued by this element, as it resembled gold, in that the most powerful acid known at that time was unable to dissolve it.

Sources

The world production of antimony in 2009 was approximately 160,000 mt per year, of which China produced up to 120,000 mt. China leads in terms of production and in converting antimony concentrates to trioxide.  Although in Europe and the USA there is little production, Spain is a producer and there are a few facilities such as Sica and Campine (Belgium), which convert antimony metal to trioxide.  The total world reserves of antimony are thought to be in the region of 2,000,000 mt.  The main recycling option for antimony is from spent lead-acid batteries mainly recovered from old cars which now are made using other types, such as the flooded-cell and Absorbed Glass Mat Battery (AGM).  Heavy machinery and vehicles, however, still use the high-antimony alloys in their batteries.

Uses

Antimony had been used for millennia without the exact knowledge of what it was.  In its initial use, stibnite was used as what is known today as ‘kohl’ for black eye make-up and as a black pigment used by artists.  Today the main consumption of antimony is in fire-retardants and plastics; indeed, the primary consumption of antimony within the EU is in flame-retardant plastic, both PVC and non-PVC, comprising 37% of the EU market.  Antimony increases flame retardant effectiveness when it is used as a synergist with halogenated flame retardants in plastics, paints, adhesives, sealants, rubber and textile back coatings.  Its properties make it possible for plastics to be used in applications where, under normal circumstances they should melt, such as in computer casings and televisions.

Antimony is also used as a major catalyst in the manufacture of PET plastic (Polyethylene terephthalate) used as drinks’ bottles and packaging.  Its other slightly smaller applications are as follows:

• as an ingredient in zinc-oxide varistors
• as a clarifying aid in certain types of glass
• as a flocculant used in the production of titanium dioxide pigments
• as a component in the manufacture of complex inorganic coloured rutile pigments
• as an opacifier in cast iron bath and sink enamelling.

Finally, highly pure antimony (99.999%) is used in semi-conductors in the computer industry.

Antimony is actually substitutable in its applications by many other elements, for example, by chromium (Cr), tin (Sn), zinc (Zn), and titanium (Ti) compounds in the paint industry; by cadmium (Cd), sulphur (S), copper (Cu), and calcium (Ca) to harden lead (Pb), and a number of organic compounds can be used as fire retardants.  It is an element which is likely to meet demand in the near future, as there is sufficient recycling and production of antimony from mining and smelter production.