The influence of pyrite on the solubility of minjingu and panda phosphate rocks

Abstract

A laboratory study was conducted to investigate the effect of pyrite rock on the solubility of Minjingu and Panda phosphate rocks. The rocks were ground to 100 mesh (0.045 mm) after which each phosphate rock was mixed with pyrite at P:S ratios of 1:4, 1 :3, 1:2, 1:1, 2:1, and 3: 1. The mixtures were moistened and incubated at 250 C. A sample was taken weekly from the mixtures and tested for pH, soluble P, Al and Mn. Results showed that mixing phosphate rocks with pyrite lower the pH and increases water soluble P of the incubation mixture. This effect was higher with Panda than with Minjingu phosphate rock. Mixing Panda phosphate rock with pyrite also resulted into high amounts of A I and Mn being released in solution. The rate of P release increased with the period of incubation up to the constant value. In mixtures with low P:S ratios this point was attained earlier than those with high P:S ratios.

Keywords: Pyrite rocks, minjingu rocks, panda phosphate rocks, incubation mixture

Tanzania J. Agric. Sc. (1998) Vol 1, No.2, 157-166