Impact of humate complexation on the adsorption of REE onto Fe oxyhydroxide

摘要: Adsorption experiments of rare-earth elements (REE) onto hydrous ferric oxide (HFO) were performed to evaluate the impact organic complexation on both REE(III) adsorption and Ce(III) oxidation rate. Scavenging at pH 5.2 with NaCl NaNO3 solutions containing either free REE (III) or REE(III)-humate complexes. The log K(d)(REE) patterns obtained from HFO suspensions exhibit a slight positive Ce anomaly an M-type lanthanide tetrad effect, in contrast partitioning between complexes HFO, which yields completely flat distribution patterns. "organic" runs yield K(d)(REEorganic)/log K(d)(DOC) ratios (DOC = dissolved carbon) close 1.0, implying that humate remain bound each other during experiment. lack any effect seems reflect anionic REE-humate complex. takes place via side by Fe(III) proportion surface hydroxyl groups coordinated are two most commonly invoked processes for explaining development anomalies effect. However, such cannot proceed since not direct contact suspensions, latter being shielded PHA. present results further complicate use as reliable paleoredox proxies natural precipitates. They also demonstration matter may inhibit geological samples.