載鐵物質 (DESFERRIOXAMINE-B) 與含磷鐵鋁礦物之間的化學反應機制

Abstract

Nutrient uptake of plants from soil is a complex process determined by the interactions of the plant roots with the soil and the combination of physical and biochemical properties of the soil. The roots of graminaceous monocots secrete phytosiderophores (PSs), which are chelating agents with a high affinity for Fe(III), to dissolve Fe(III) in soil. The release of PSs can potentially mobilize nutrients, such as P, associated with Fe in soil. To understand the potential role of PSs in regulating the P acquisition of plants, this study investigated the interactions of desferrioxamine-B (DFO-B) siderophore with some major Fe, Al and P - containing minerals, including strengite (FePO4∙2H2O), variscite (AlPO4∙2H2O), and phosphate-loaded goethite (α-FeOOH), gibbsite (α-Al(OH)3) and hematite (α-Fe2O3). The pseudo-first-order rate constant was determined for the DFO-B – promoted dissolution of each mineral and subsequently normalized to the corresponding amount of adsorbed siderophore to calculate the mass-normalized dissolution rate. Apparent activation energies (Ea) were calculated from the mass-normalized dissolution rates of each mineral obtained at different temperatures using the Arrhenius equation. Increasing the loading of adsorbed P on all three oxides (i.e., goethite, hematite and gibbsite) resulted in an increase in the dissolution rates of the minerals but a decrease in dissolution rates at pH 9. The rate inhibition at pH 9 is attributed to the presence of binuclear surface complexes, in which much more energy is required to remove simultaneously two center atoms from the crystalline lattice than it is to remove solely one center (i.e. in the case of mononuclear complexes at pH 4). Higher Ea values at pH 9 than at pH 4, supports our hypothesis that the existence of stronger adsorbed phosphate complexes hinder the smooth release of the metal-ion-center. DFO-B -promoted dissolution of strengite and variscite studies show that dissolution was enhanced in the presence of DFO-B. Higher dissolution rates for variscite than strengite is attributed to the higher adsorbed concentrations of DFO-B on variscite than on strengite.