Ask: What is the relationship between ammonium metatungstate (AMT) and rewriting paper?

Answer: Nothing direct.

Ask: Then, why you put both of them together?

Answer: Because ammonium metatungstate is the raw material for preparing tungsten dioxide (WO₂), while tungsten dioxide is one of the two material of rewriting paper.

 

Paper wasting is one of the biggest problems we meet in environment protection currently, we know that, the raw materials of papermaking are plant fiber (such as woods, bamboo, grass), mineral fiber (asbestos, glass fiber, etc), other fiber (nylon, metal wire, etc.), and the polymer material which get from oil cracking. At present, papers used for writing, painting and packing are still manufacturing from plant fiber, which will bring huge threat to environment protection.

 

Recently, one research team came up with an interesting solution – the rewriting paper, which is using two materials of tungsten dioxide (WO₂) and polyvinyl pyrrolidone; this rewriting paper not only can save water, energy, space, but also can reduce the emissions of greenhouse gas; in addition, this kind of rewriting paper has non-toxic effect, and has been proved to be used for the field of medicine and food. The rewriting paper is through the appearing and fading of blue to realize function of rewriting, if this material is exposed to UV light for more than 30 seconds, the color will automatically become dark blue; while, the blue will fade when exposed in the outdoor for a or two days, or heated; moreover, the addition of polyvinyl pyrrolidone can extend the duration of blue to 10 days, and increase circulation writing to 40 times.

 

Ammonium metatungstate is a kind of white or yellowish powder with water solubility, and the solubility can reach to 300g/100ml in the water under 20°C, an important tungsten compound in tungsten metallurgy industry. Ammonium metatungstate is mainly used for preparing tungsten oxide, such as tungsten trioxide (WO₃), tungsten dioxide (WO₂), blue tungsten oxide (WO_2.9) and violet tungsten oxide (WO_2.72), tungsten powder, tungsten based carbide; furthermore, AMT is also used in many kinds of petroleum and chemical catalysts, the main raw material of W-based catalyst for oil refineries.