Potassium (K) and water
Potassium and water: reaction mechanisms, environmental impact and health effects
|Seawater contains about 400 ppm potassium. It tends to settle, and consequently ends up in sediment mostly. Rivers generally contains about 2-3 ppm potassium. This difference is mainly caused by a large potassium concentration in oceanic basalts. Calcium rich granite contains up to 2.5% potassium. In water this element is mainly present as K+ (aq) ions. |
40K is a naturally abundant radioactive potassium isotope. Seawater contains a natural concentration of about 4.5 . 10-5 g/L.
Potassium reacts rapidly and intensely with water, forming a colourless basic potassium hydroxide solution and hydrogen gas, according to the following reaction mechanism:
2K (s) + 2H2O (l) -> 2KOH (aq) + H2 (g)
Potassium is non-water soluble, but it does react with water as was explained earlier. Potassium compounds may be water soluble. Examples are potassium dichromate with a water solubility of 115 g/L, potassium permanganate with a water solubility of 76 g/L, potassium iodide with a water solubility of 92 g/L, and potassium iodide, of which even up to 1480 g may be dissolved in one litre of water.
Potassium occurs in various minerals, from which it may be dissolved through weathering processes. Examples are feldspars (orthoclase and microcline), which are however not very significant for potassium compounds production, and chlorine minerals carnalite and sylvite, which are most favourable for production purposes. Some clay minerals contain potassium. It ends up in seawater through natural processes, where it mainly settles in sediments.
Potassium is an dietary requirement for nearly any organism but a number of bacteria, because it plays an important role in nerve functions.
Potassium is a dietary requirement for us, and we take up about 1-6 g per day at a requirement of 2-3.5 g per day. The total potassium amount in the human body lies somewhere between 110 and 140 g and mainly depends upon muscle mass. The muscles contain most potassium after red blood cells and brain tissue.
Potassium may be removed from water by means of reverse osmosis.