Recovery of Phosphorus from Low-Grade Ores and Waste Materials Via Bioleaching As a Function of Poorly Crystalline Fe/Al Mineral Content.

Phosphorus fertilizers are essential to increase agronomic yields and maintain or attain food security for a growing global population; however, some estimates indicate that economic rock phosphate reserves may become a regionally-critical resource within the next century.  The future supply of rock phosphate is expected to become progressively lower in quality, contaminated foremost with cadmium and uranium, less accessible and more unequally distributed around the world.  There is thus a need for efficient, cost effective treatment technologies to recover fertilizer-grade phosphorus from unexploited resources such as low-grade phosphate reserves, sub-economic rock phosphate deposits, waste rock, tailings, or other phosphorus-containing waste materials.  This in turn will contribute to global food security by providing a low-cost form of the phosphorus that is essential for food production, thereby reducing dependence on non-renewable high-grade rock phosphate reserves.  Partial acidulation of rock phosphate with mineral acid or biological leaching of phosphorus-containing materials may be viable alternative treatment techniques for the recovery of phosphate from solid materials containing relatively low levels of phosphorus, or which are otherwise difficult to handle or treat.  In this study, phosphorus-solubilizing bacteria were isolated from selected Australian apatite ores and identified using 16S RNA gene sequencing.  We quantified phosphorous solubilization via bioleaching using isolated phosphorus solubilizing bacteria and partial acidulation with mineral acid, respectively, as a function of poorly crystalline oxide/(oxy)hydroxide mineral content using a range of rock phosphate ores.  The results obtained provide a baseline understanding of phosphorus solubilization from partially acid leached and biologically leached apatite as a function of time.  Ultimately this knowledge will contribute to the optimization of bioleaching technologies for the generation of partially acidulated rock phosphate from low-grade phosphate mineral resources and other sub-economic mineral P reserves for use as slow-release P fertilizer.