Adsorption and co‐precipitation reactions at the mineral‐fluid interface: natural and anthropogenic processes

The processes of adsorption and co‐precipitation at mineral surfaces during reactions with aqueous fluids play a critical role in controlling the mass transfer and bioavailability of nutrients and contaminants. Significant advances have been made in our understanding of these two processes through the application of synchrotron‐based analytical techniques including X‐ray Absorption Spectroscopy (XAS), X‐ray surface scattering methods, X‐ray fluorescence, and glancing incidence diffraction. Along with these methodologies, a wide range of other techniques involving infra‐red spectroscopy, atomic‐force microscopy, electron and particle beams have also contributed to understanding atomic‐scale processes at mineral surfaces. Here, the basics of each of these synchrotron methods are introduced along with an illustrative example from the literature. The allied techniques are also discussed. After this introduction, two case studies dealing with major contemporary environmental problems that involve adsorption and co‐precipitation are presented. The first concerns the mobility of arsenic in groundwater. Currently, dissolved arsenic species pose an environmental threat to millions of people. The second case study considers the speciation and uptake of uranium within UK radioactive waste sludge. Clean‐up of these sludges is expected to be a challenging technological problem, and the insights provided through understanding the attachment of the uranium to the sludge minerals may be critical to devising a successful remediation strategy.