Measurement of acid attack on phosphate rocks

A continuous analyser of thermometric type was modified and connected to a batch reactor to obtain quick kinetic curves of phosphate rock acid attack. Different kinds of rocks and two acids were tested in the physical conditions where the dissolution velocity is slow (diluted solutions and low temperatures). A mass transfer model, based on calcium diffusion from the rock particle to the liquid bulk, was verified, although at the beginning of the reaction a delay (as yet of unknown origin) appeared as described in the literature.