Potassium: Reversible binding of ions (07/03/22 18:46:09)
"Zeolites have a porous structure that can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+ and others. These positive ions are rather loosely held and can readily be exchanged for others in a contact solution. Some of the more common mineral zeolites are analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, and stilbite. An example of the mineral formula of a zeolite is: Na2Al2Si3O10·2H2O, the formula for natrolite. Cation exchanged zeolites possess different acidity and catalyse different reactions.[non-primary source needed]
Natural zeolites form where volcanic rocks and ash layers react with alkaline groundwater. Zeolites also crystallize in post-depositional environments over periods ranging from thousands to millions of years in shallow marine basins. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, metals, quartz, or other zeolites. For this reason, naturally occurring zeolites are excluded from many important commercial applications where uniformity and purity are essential."
So zeolites are candidates for potassium recovery from sewage and seawater. But from there wehave a long and thorny road in technology development: How is recovery of the salt to be done? How is the concentrated solution going to be made in an energy-responsible way? How is fouling of the absorbent by algae andbacteria to be avoided? What is to be done with end-of-useful-life-material? Landfill is not an option.
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