Effect of pulp density on acidulation mechanisms in low-grade phosphate rock using biogenic acid generated by Acidithiobacillus thiooxidans.

Sandra Restrepo , Henry Alonso Colorado Lopera, Marco Antonio Márquez Godoy

Phosphorus is essential for global food security, but traditional extraction using thermal and hydrometallurgical methods is hampered by the depletion of deposits and high energy costs. This study evaluates the recovery of low-grade Colombian phosphate rock (5.5% w/w P) through biogenic leaching. Unlike chemical acidulation, which consumes a lot of water and tends to produce disruptive foam, this biotechnological approach offers a controlled and sustainable alternative.
A biological leaching agent was obtained using Acidithiobacillus thiooxidans (ATCC 13977), with systematic control of pH, sulfate generation, and biomass kinetics. The process was tested with pulp densities of 20% and 30% (w/w). Comprehensive characterization using XRF, XRD, FTIR, and SEM-EDS revealed significant mineralogical transformations and morphological changes in the residues. UV-Vis spectroscopy confirmed the effective solubilization of P.
By operating at room temperature and replacing concentrated chemical reagents, this method significantly reduces the carbon and water footprint. The results demonstrate that bioleaching is a technically viable circular approach to transforming mineral waste into strategic nutrients. This research promotes technological sovereignty and industrial sustainability by providing an efficient way to use low-value natural resources.