Carbonate species are abundant in the environment, continuously interacting with other ions and minerals, and directly influencing their aqueous equilibria. The ability of carbonate to strongly sorb onto minerals surfaces, such as iron oxides, affects the sorption of other oxyanions since carbonate species compete for binding sites of metal oxides. The increasing atmospheric world CO2 concentration, besides contributing to global warming, has prominent implications on adsorption equilibria as well. Although elucidating the carbonate adsorption on iron oxides under different atmospheric CO2 concentrations is imperative, the development of an experimental set-up is a challenge in itself, and thus studies on CO2 adsorption are rather scarce. For ferrihydrite, the only carbonate adsorption data available come from batch experiments measured with 14C (Zachara et al., 1987), which do not reflect the behavior under open atmospheric conditions. Recently, we have rebuilt the set – up previously used to quantify carbonate adsorption on goethite (Villalobos et al., 2000), by measuring the CO2 indirectly using an infrared director. This set – up allows the simulation of both open (constant pressure) and closed (fixed amount of total CO2) atmospheric conditions. In this study, we have quantified carbonate adsorption under open atmosphere, and specifically for two PCO2, 400 and 600 ppm, at a pH range 4 – 11. The results showed continuous increase of carbonate adsorption with pH for both pressures. The data collected were used for the calibration of a surface complexation model of carbonate on ferrihydrite.

Carbonate adsorption on ferrihydrite under atmospheric conditions: Experimental and modeling

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.