Arsenite and Arsenate Sorption to Biogenic Iron (Oxyhydr)Oxides Formed in Natural and Laboratory Environments.

Arsenic (As) is a widespread and problematic pollutant that can be derived from natural or anthropogenic sources. Iron (oxyhydr)oxides readily sorb arsenic and thus they play critical roles in arsenic cycling in terrestrial environments; however, little is known concerning the affinity and mechanism of As(III/V) sorption by biogenic iron (oxyhydr)oxides formed in natural hydrological environments. To investigate this, we conducted adsorption isotherm and kinetics experiments to compare As(III) and As(V) sorption to iron (oxyhydr)oxides produced by neutrophilic iron oxidizing bacteria and those harvested from circumneutral pH waters. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify both As(III) and As(V). Scanning electron microscopy (SEM) was used to probe mineral morphology, whereas X-ray adsorption spectroscopy (XAS) was utilized to determine mineral structure and local As binding structure. This study helps to improve our understanding of the sorption reactivity of biogenic iron (oxyhydr)oxides for environmentally relevant As species (III and V) and is critical to understanding As cycling in natural systems while also having the potential to improve As remediation systems.