Relative importance of protons and solution calcium concentration in phosphate rock dissolution by organic acids

TLDR: A series of experiments was conducted to quantify the relative contribution of protons and other mechanisms to the dissolution of phosphate rocks (PRs) from six countries in solutions of low-molecular-weight aliphatic organic acids as mentioned in this paper.

Abstract: A series of experiments was conducted to quantify the relative contribution of protons and other mechanisms to the dissolution of phosphate rocks (PRs) from six countries in solutions of low-molecular-weight-aliphatic organic acids. The amounts of P and Ca released after 3 d of incubation at 28°C were determined in all the experiments. In the first experiment the solubility of the PRs < 500 μm particle size) in 100 M (25 mL g-1 PR) oxalic, tartaric, and citric acids was compared with that in three mineral acids and four chelating compounds. There were no differences in the amount of P released by the mineral acids, but the organic acids released more P than could be accounted for by protonation. The chelating compounds were the least effective. In the second experiment, 1 g each of Sri Lanka and Togo PRs was incubated with 2.5 mmol of the organic acids using three acid concentration (mM) : acid volume ratios (250:10, 100:25, and 25:100). The amount of P dissolved from the PRs and the amount of ac...