Publication Date:
2020-02-12
Description:
RECAWA intends to develop a fundamental understanding of the reactivity and dynamics of calcite surfaces during crystal growth in aquatic systems. Therefore, the calcite-water surface has been characterised at different hydrochemical conditions and surface diffraction measurements have been applied to probe if changes in zeta potential are accompanied by changes in the calcite-water interface structure. The interaction of calcite with Selenium is investigated in a mixed flow reactor (MFR) study which is accompanied by GI- EXAFS analyses to characterize the Se adsorption species. The interaction of calcite surfaces with phosphate and phosphonates is the focus of two subprojects. The sorption/precipitation mechanisms of PO43- and HPO32+, respectively, on different calcite powders (precipitated calcium carbonates and limestone powders) are investigated to determine sorption isotherms and phase transformations on the applied surfaces which is of great interest with regard to phosphate recycling and/or water treatment. Analytical work includes SEM, XRD and XAFS spectroscopy for a detailed characterisation of the calcite powders in different sections of the isotherms. Experimental investigations on the interaction of limestone powder and two superplasticizers have been conducted with regard to concreting. These experiments were done at alkaline conditions and lead to massive reactions and changes in the zeta potential of the solutions and limestone powder when superplasticizers added. Additional results of quantum-mechanical calculations and force-field modelling demonstrated that the Double Defect Method is able to quantitatively predict mixing properties of various isostructural binary and ternary carbonate solid solutions. In particular, low equilibrium retention levels of SO42- and SeO42- in carbonates imply that the reasonably large concentrations SO42- and SeO42- in carbonates reported in previous studies should be attributed to non-equilibrium entrapment effects. Data obtained from atomistic modelling complement our data determined using lab methods. Further experimental and analytical, work including in-situ AFM studies using Iceland spar single crystals, is in progress and will help to interconnect the present results of the sub-projects.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
Format:
application/pdf
Permalink
