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<p>This study investigates the dissolution kinetics of a sedimentary phosphate ore sourced from the Djebel Onk deposit (Algeria) in dilute H<sub>2</sub>SO<sub>4</sub>, with the objective of supporting the optimization of wet-process phosphoric acid production. The ore, primarily composed of fluorapatite associated with carbonate gangue minerals (calcite and dolomite) and containing 23–26% P<sub>2</sub>O<sub>5</sub>, was leached at ambient temperature using 3% H<sub>2</sub>SO<sub>4</sub>. To assess the dissolution behavior of magnesium-bearing carbonates, the release of Mg<sup>2</sup>⁺ was monitored throughout the leaching experiments. In addition, experiments were conducted across various particle size fractions to evaluate the influence of granulometry on the dissolution process. The kinetic data were interpreted using two complementary modeling approaches: a first&#xa0;order reaction model and a non-linear dependence model accounting for ion exchange phenomena. The results reveal a significant dependence of dissolution behavior on particle size. Specifically, application of the first&#xa0;order model to the coarse fraction (− 1.25 + 0.08&#xa0;mm) yielded a dissolution rate constant (k) of 0.10 ± 0.01&#xa0;min⁻<sup>1</sup> and an equilibrium Mg concentration of 0.82 ± 0.03&#xa0;g/L. In contrast, for the finer fraction (− 0.5 + 0.1&#xa0;mm), while the rate constant remained comparable at 0.09 ± 0.01&#xa0;min⁻<sup>1</sup>, the equilibrium Mg concentration increased markedly to 2.96 ± 0.17&#xa0;g/L. Furthermore, the more complex dependence model confirmed that particle size influences the underlying dissolution mechanism. Although the rate constant remained stable (~ 0.09&#xa0;min⁻<sup>1</sup>) for both fractions, the finer fraction exhibited a reduced dependence on ion exchange (with an estimated ion exchange parameter of 0.5) compared to the coarser fraction (1.02), thereby indicating a shift in the rate-limiting step. Taken together, these findings highlight that both granulometry and ionic interactions are critical factors governing the dissolution kinetics of phosphate ore in sulfuric acid. Consequently, this underscores the need to tailor operating conditions to specific mineral fractions in order to optimize the recovery of magnesium and, by extension, other associated elements.</p>

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Kinetic modeling of sulfuric acid leaching for phosphate rock dissolution

  • 期刊论文

  • 发表日期：

    2026年4月7日

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  • Saida Yakoubi,
  • Louisa Bounemia,
  • Hocine Boutoumi,
  • Hussein Khalaf

摘要

This study investigates the dissolution kinetics of a sedimentary phosphate ore sourced from the Djebel Onk deposit (Algeria) in dilute H2SO4, with the objective of supporting the optimization of wet-process phosphoric acid production. The ore, primarily composed of fluorapatite associated with carbonate gangue minerals (calcite and dolomite) and containing 23–26% P2O5, was leached at ambient temperature using 3% H2SO4. To assess the dissolution behavior of magnesium-bearing carbonates, the release of Mg2⁺ was monitored throughout the leaching experiments. In addition, experiments were conducted across various particle size fractions to evaluate the influence of granulometry on the dissolution process. The kinetic data were interpreted using two complementary modeling approaches: a first order reaction model and a non-linear dependence model accounting for ion exchange phenomena. The results reveal a significant dependence of dissolution behavior on particle size. Specifically, application of the first order model to the coarse fraction (− 1.25 + 0.08 mm) yielded a dissolution rate constant (k) of 0.10 ± 0.01 min⁻1 and an equilibrium Mg concentration of 0.82 ± 0.03 g/L. In contrast, for the finer fraction (− 0.5 + 0.1 mm), while the rate constant remained comparable at 0.09 ± 0.01 min⁻1, the equilibrium Mg concentration increased markedly to 2.96 ± 0.17 g/L. Furthermore, the more complex dependence model confirmed that particle size influences the underlying dissolution mechanism. Although the rate constant remained stable (~ 0.09 min⁻1) for both fractions, the finer fraction exhibited a reduced dependence on ion exchange (with an estimated ion exchange parameter of 0.5) compared to the coarser fraction (1.02), thereby indicating a shift in the rate-limiting step. Taken together, these findings highlight that both granulometry and ionic interactions are critical factors governing the dissolution kinetics of phosphate ore in sulfuric acid. Consequently, this underscores the need to tailor operating conditions to specific mineral fractions in order to optimize the recovery of magnesium and, by extension, other associated elements.