The kinetics of rare earth element interactions with synthetic and naturally occurring polyelectrolytes

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5730318

Clark, S B

This research is an investigation of the kinetics of formation and dissociation of complexes of trivalent lanthanide ions with the polyelectrolytes polyacrylic acid and humic acid. Theories of cation binding to charged polymers have defined two types of interactions: site binding, which involves complexation by a specific ligand group on the polyion, and territorial binding that is a non-specific, charge neutralization interaction. The speciation of trivalent lanthanides and actinides in the environment may be dominated by complexation with naturally occurring polymers. Therefore, knowledge of the rates of these interactions is important in modeling the environmental behavior of these cations in natural systems. Ultrafiltration and ion exchange studies indicate that under the conditions of this study, complexation is fast and complete, but slowly changes from the initially labile interactions to a distribution of the cations between labile sites and longer lived binding sites. This change in binding occurs by a cooperative binding mechanism that includes two processes. Relatively rapid diffusion of the metal ions into sites within the coiled structure of the polyion can occur along with slower polymer configurational changes that can create less labile, previously inaccessible sites. Decomplexation has been studied using a ligand exchange technique, and the binding sites appear to fall into two classes of interactions based on their dissociation rates. The first category of interactions dissociates rapidly, and presumably includes lanthanide ions bound to sites on the surface of the polymer as well as territorially bound cations. The second type of binding interactions is longer lived and may represent lanthanide ions complexed within the coiled structure of the polyion.

• Research Organization: Florida State Univ., Tallahassee, FL (USA)
• OSTI ID: 5730318
• Country of Publication: United States
• Language: English

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AFFINITY
CATIONS
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMISTRY
COMPLEXES
ESTERS
FILTRATION
HUMIC ACIDS
ION EXCHANGE
IONS
KINETICS
LIGANDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
POLYMERS
POLYVINYLS
RARE EARTH COMPLEXES
REACTION KINETICS
SEPARATION PROCESSES
SOIL CHEMISTRY