Example – oxidation of manganese dioxide
Generic product activity or name
KMn04 and K2CO3, potassium permanganate, potassium carbonate
Context and background
Manganese dioxide is an inorganic compound with the formula MnO2 which is a precursor for KMnO4 (Potassium permanganate) and K2CO3 (Potassium carbonate)(Open Chemistry Database 2015a and 2015b).
Potassium permanganate is a strong oxidizing agent and is used as an oxidizing agent in many chemical reactions. It is used as an antiseptic and as an antifungal treatment as well as to prolong the shelf life of some fruits. It is also used extensively for wastewater treatment and against certain invasive species such as the zebra mussels. Potassium carbonate is a white salt, soluble in water, where it forms a strong alkaline solution. Potassium carbonate is used in such products as soap and glass and as a corrosion inhibitor.
Presentation of example
The activity “oxidation of manganese dioxide” (present in the ecoinvent database v3.0) has two co-products: potassium permanganate and potassium carbonate. The manganese dioxide (MnO2) is fused with potassium hydroxide and heated with a source of oxygen to give potassium manganate:
2 MnO2 + 4 KOH + O2 → 2 K2MnO4 + 2 H2O
Boiling the manganate solution in the presence of carbon dioxide then gives potassium permanganate and potassium carbonate:
3 K2MnO4 + 2 CO2 → 2 KMnO4 + 2 K2CO3 + MnO2
Although there are other possible ways of production, the described activity is the only industrial production route for potassium permanganate.
For potassium carbonate, the current predominating manufacturing process is by electrolysis of potassium chloride followed by carbonation using carbon dioxide (Open Chemistry Database – PubChem 2015b, Wikipedia 2015):
2KOH + CO2 → K2CO3 + H2O
Because potassium permanganate does not have any other industrial production routes, while potassium carbonate has another production route, we can identify potassium permanganate as the determining product, while potassium carbonate is identified as a dependent by-product of the “oxidation of manganese dioxide” activity.
Information sources used
Ullmann’s Encyclopedia of Industrial Chemistry is the classic reference work related to industrial chemistry, which is also published online. Another good source is the Open Chemistry Database, which has the added benefit of being free of charge. Wikipedia is also an excellent starting place for these chemicals.
Open Chemistry Database – PubChem (2015a) – Potassium Permanganate. National Center for Biotechnology Information. http://pubchem.ncbi.nlm.nih.gov/compound/potassium_permanganate (accessed June 8, 2015)
Open Chemistry Database – PubChem (2015b) – Potassium carbonate. National Center for Biotechnology Information. http://pubchem.ncbi.nlm.nih.gov/compound/potassium_carbonate (accessed June 8, 2015)
Wikipedia 2015 – Potassium carbonate
http://en.wikipedia.org/wiki/Potassium_carbonate (accessed June 8, 2015)
Ullmann’s Encyclopedia of Industrial Chemistry 7th ed. (1999-2012). NY, NY: John Wiley & Sons: http://onlinelibrary.wiley.com/book/10.1002/14356007
Author of this example
How to reference this
Weidema B P (2014), Example –oxidation of manganese dioxide. Version: 2014-01-30 www.consequential-lca.org