Beneficiation of creek calcareous phosphate ore using acetic acid solutions

The enrichment of the low-grade natural phosphate ores from Epirus area (Greece) by selective dissolution of calcite using dilute acetic acid and the optimization of this process studied by kinetic and textural analysis is given. The used conditions of the dissolution were the reaction time, stirring speed, acetic acid concentration, temperature, particle size fraction, and stoichiometry. The specific surface area, pore size distribution, and SEM photographs were used for textural analysis. We found that the more effective experimental conditions led to a concentration of about 31% of P2O5 or 95% of francolite. The dissolution of calcite spaces took place in two steps. The first step was attributed to the dissolution of liberated calcite particles and/or spaces on the particles, and the second one was attributed to the dissolution of calcite in the interspaces between phosphopeloids. A rate equation of the general form ln[1/(1-X)] = kt(m) was found to represent these data.