Foszfátionok

Foszfátionok, or phosphate ions, are inorganic anions derived from phosphoric acid and its successive deprotonations. The term covers orthophosphate species such as PO4^3− and its protonated forms, as well as condensed phosphates like pyrophosphate (P2O7^4−) and tripolyphosphate (P3O10^5−). In aqueous solution, the relative amounts of these species depend strongly on pH.

At low pH, H3PO4 is present; near neutral pH the dominant species are H2PO4− and HPO4^2−, while at higher pH PO4^3− becomes prevalent. The approximate pKa values are 2.1, 7.2, and 12.3, which explains the buffering action of the phosphate system around physiological pH. Phosphates readily form complexes with metal ions such as Ca^2+, Mg^2+, and Fe^3+, and they can participate in precipitation reactions to form metal phosphates.

Occurrence and biological relevance: foszfátionok occur naturally in rocks (as apatite), soils, and water bodies, and are essential nutrients for plants and animals. They are central to biology, forming the backbone of nucleic acids (DNA and RNA) and energy carriers like ATP.

Applications: phosphate salts are used as fertilizers, food additives, buffering agents, and sequestering agents in water treatment. Polyphosphates are employed in detergents and industrial processes to bind hardness-causing cations and to stabilize formulations. They can influence water chemistry by preventing scale or, conversely, by contributing to eutrophication if released in excess.

Environmental considerations: phosphate runoff can stimulate algal blooms and eutrophication; many jurisdictions regulate phosphate discharges and ban certain phosphate-containing detergents.