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<p> Purpose: We investigated the influence of residence time on phosphorus (P) sorption by the main clay-sized minerals of Oxisols (kaolinite, gibbsite, hematite, and goethite) and its subsequent extractability using Mehlich I solution (0.0500&#xa0;M HCl + 0.0125 M H<sub>2</sub>SO<sub>4</sub>). Additionally, we assessed the application of X-ray photoelectron spectroscopy (XPS) for detecting residual P on mineral surfaces following extraction with that solution. Methods: Natural kaolinite and synthetic gibbsite, hematite, and goethite samples were analyzed by X-ray diffraction to assess mineralogical purity and by nitrogen adsorption to determine specific surface area. Batch sorption experiments were performed under acidic condition (pH 4.5) to determine P sorption isotherms over 24&#xa0;h and to assess P sorption kinetics across residence times ranging from 3 to 912&#xa0;h. At 3 and 912&#xa0;h, P was extracted using Mehlich I solution. Subsequently, the minerals were washed with deionized water, lyophilized, and analyzed by XPS. Results: Kaolinite exhibited slow P sorption but nearly complete extractability with Mehlich I solution, even after 912&#xa0;h of residence time. In contrast, goethite showed rapid P sorption and the lowest extractability. Both gibbsite and hematite exhibited reduced P extractability as residence time increased from 3 to 912&#xa0;h, with hematite contributing more significantly to non-labile P formation than gibbsite. XPS analysis detected residual P within the top ~ 2.5&#xa0;nm of the gibbsite, hematite, and goethite surfaces. Conclusions: Temporal effects on P sorption and sequestration varied among minerals, with goethite acting as the primary P immobilizer and kaolinite showing minimal P fixation. Combined extraction and XPS data suggested that the rapid formation of stable surface complexes on goethite and the temporal reorganization of these complexes on gibbsite and hematite, rather than intraparticle diffusion alone, limit complete P extraction from these iron and aluminum (hydr)oxides by Mehlich I solution.</p>

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Residence Time Effects on the Sorption and Extraction of Phosphorus by Mehlich I Solution in Typical Clay-Sized Minerals of Oxisols

  • 期刊论文

  • 发表日期：

    2025年12月17日

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  • Nathália Cristina Marchiori Pereira,
  • Flávio César Vicentin,
  • Maksuda Kathun,
  • Marcelo Eduardo Alves

摘要

Purpose: We investigated the influence of residence time on phosphorus (P) sorption by the main clay-sized minerals of Oxisols (kaolinite, gibbsite, hematite, and goethite) and its subsequent extractability using Mehlich I solution (0.0500 M HCl + 0.0125 M H2SO4). Additionally, we assessed the application of X-ray photoelectron spectroscopy (XPS) for detecting residual P on mineral surfaces following extraction with that solution. Methods: Natural kaolinite and synthetic gibbsite, hematite, and goethite samples were analyzed by X-ray diffraction to assess mineralogical purity and by nitrogen adsorption to determine specific surface area. Batch sorption experiments were performed under acidic condition (pH 4.5) to determine P sorption isotherms over 24 h and to assess P sorption kinetics across residence times ranging from 3 to 912 h. At 3 and 912 h, P was extracted using Mehlich I solution. Subsequently, the minerals were washed with deionized water, lyophilized, and analyzed by XPS. Results: Kaolinite exhibited slow P sorption but nearly complete extractability with Mehlich I solution, even after 912 h of residence time. In contrast, goethite showed rapid P sorption and the lowest extractability. Both gibbsite and hematite exhibited reduced P extractability as residence time increased from 3 to 912 h, with hematite contributing more significantly to non-labile P formation than gibbsite. XPS analysis detected residual P within the top ~ 2.5 nm of the gibbsite, hematite, and goethite surfaces. Conclusions: Temporal effects on P sorption and sequestration varied among minerals, with goethite acting as the primary P immobilizer and kaolinite showing minimal P fixation. Combined extraction and XPS data suggested that the rapid formation of stable surface complexes on goethite and the temporal reorganization of these complexes on gibbsite and hematite, rather than intraparticle diffusion alone, limit complete P extraction from these iron and aluminum (hydr)oxides by Mehlich I solution.