Visualizing Organophosphate Precipitation at the Calcite-Water Interface by in Situ Atomic-Force Microscopy
MetadataShow full item record
Esters of phosphoric acid constitute a large fraction of the total organic phosphorus (OP) in the soil environment and, thus, play an important role in the global phosphorus cycle. These esters, such as glucose-6-phosphate (G6P), exhibit unusual reactivity toward various mineral particles in soils, especially those containing calcite. Many important processes of OP transformation, including adsorption, hydrolysis, and precipitation, occur primarily at mineral–fluid interfaces, which ultimately governs the fate of organophosphates in the environment. However, little is known about the kinetics of specific mineral-surface-induced adsorption and precipitation of organophosphates. Here, by using in situ atomic-force microscopy (AFM) to visualize the dissolution of calcite (1014) faces, we show that the presence of G6P results in morphology changes of etch pits from the typical rhombohedral to a fan-shaped form. This can be explained by a site-selective mechanism of G6P–calcite surface interactions that stabilize the energetically unfavorable (0001) or (0112) faces through step-specific adsorption of G6P. Continuous dissolution at calcite (1014)–water interfaces caused a boundary layer at the calcite–water interface to become supersaturated with respect to a G6P–Ca phase that then drives the nucleation and growth of a G6P–Ca precipitate. Furthermore, after the introduction of the enzyme alkaline phosphatase (AP), the precipitates were observed to contain a mixture of components associated with G6P–Ca, amorphous calcium phosphate (ACP)–hydroxyapatite (HAP) and dicalcium phosphate dihydrate (DCPD). These direct dynamic observations of the transformation of adsorption- and complexation-surface precipitation and enzyme-mediated pathways may improve the mechanistic understanding of the mineral-interface-induced organophosphate sequestration in the soil environment.
Showing items related by title, author, creator and subject.
Imaging Organophosphate and Pyrophosphate Sequestration on Brucite by in Situ Atomic Force Microscopy.Wang, L.; Putnis, C.; King, H.; Hövelmann, J.; Ruiz-Agudo, E.; Putnis, Andrew (2016)In order to evaluate the organic phosphorus (OP) and pyrophosphate (PyroP) cycle and their fate in the environment, it is critical to understand the effects of mineral interfaces on the reactivity of adsorption and ...
Renard, F.; Røyne, A.; Putnis, Christine (2018)In the Earth's upper crust, where aqueous fluids can circulate freely, most mineral transformations are controlled by the coupling between the dissolution of a mineral that releases chemical species into the fluid and ...
Stockmann, G.; Wolff-Boenisch, Domenik; Bovet, N.; Gislason, S.; Oelkers, E. (2014)The aim of this study is to illuminate how calcite precipitation depends on the identity and structure of the growth substrate. Calcite was precipitated at 25 °C from supersaturated aqueous solutions in the presence of ...