Arsenate uptake by calcite: Macroscopic and spectroscopic characterization of adsorption and incorporation mechanisms

摘要

Batch uptake experiments and X-ray element mapping and spectroscopic techniques were used to investigate As(V) (arsenate) uptake mechanisms by calcite, including adsorption and coprecipitation. Batch sorption experiments in calcite-equilibrated suspensions (pH 8.3; PCO2 = 10(-3.5) atm) reveal rapid initial sorption to calcite, with sorption rate gradually decreasing with time as available sorption sites decrease. An As(V)-calcite sorption isotherm determined after 24 h equilibration exhibits Langmuir-like behavior up to As concentrations of 300 mu M. Maximum distribution coefficient values (K-d), derived from a best fit to a Langmuir model, are similar to 190 L kg(-1). Calcite single crystals grown in the presence of As(V) show well-developed rhombobedral morphology with characteristic growth hillocks on (1 0(1) over bar