Uptake of Cu2+ by the Calcium Carbonate Minerals Vaterite and Calcite as Studied by CW and Pulse Electron Paramagnetic Resonance (EPR)

Abstract

The distribution of trace metals like Mn, Fe, Cu or Cd in the aquatic environment is regulated by redox equilibria, the complexation of the metals with organic and inorganic ligands in solution and at surfaces, and precipitation/dissolution reactions [1]. Due to the high reactivity of the widespread carbonate minerals the speciation of trace metal ions in natural waters is often controlled by carbonate and bicarbonate ions [2]. Furthermore the precipitation of carbonate minerals like calcite (CaCO3) in lakes and oceans provides important pathways of trace metal scavenging by adsorption of the metal ions and coprecipitation during crystal growth. Investigation of the molecular interactions between trace metals and carbonate minerals is relevant for the understanding of the biogeochemical cycles of the metals and their role in the processes of crystal growth and growth inhibition. Recently, the application of surface-sensitive spectroscopic and microscopic techniques has given more insight into the molecular structure and properties of calcite surfaces and provided a new basis for the interpretation of trace metal sorption on Lab. for Physical Chemistry, ETHZ, CH 8092 Ziirich, Switzerland