Speciation and release kinetics of zinc in contaminated paddy soils.

Zinc is an important nutrient for plants, but it can be toxic at high concentrations. The solubility and speciation of Zn is controlled by many factors, especially soil pH and Eh, which can vary in lowland rice culture. This study determined Zn speciation and release kinetics in Cd-Zn cocontaminated alkaline and acidified paddy soils, under various flooding periods and draining conditions, by employing synchrotron-based techniques and a stirred-flow kinetic method.

Ni(II) complexation to amorphous hydrous ferric oxide: an X-ray absorption spectroscopy study.

Ni(II) sorption onto iron oxides and in particular hydrous ferric oxide (HFO) is among the important processes impacting its distribution, mobility, and bioavailability in environment. To develop mechanistic models for Ni, extended X-ray absorption fine structure (EXAFS) analysis has been conducted on Ni(II) sorbed to HFO. Coprecipitation revealed the formation of the metastable alpha-Ni(OH)(2) at a Ni(II) loading of 3.

Sonolysis induced decomposition of metal carbonyls: kinetics and product characterization.

The decomposition kinetics of Fe(CO)5 and Mo(CO)6 induced by sonolysis in hexadecane solvent was studied as a function of temperature (303-343 K) under an inert atmosphere. The decomposition data, obtained over at least two half lives in most of the runs, yielded first-order rate constant (k) values with correlation co-efficient (R2) > 0.95.

Synthesis of zerovalent nanophase metal particles stabilized with poly(ethylene glycol).

Concurrent sonolysis of iron pentacarbonyl and poly(ethylene glycol)-400 (PEG-400) in hexadecane solvent proceeds via zero-order kinetics and results in Fe nanoparticles encapsulated in PEG-400 (Fe-PEG). The transmission electron microscopy images show Fe-PEG consisting of <3 nm Fe particles that are evenly dispersed in the PEG matrix. Mössbauer and X-ray absorption fine structure/X-ray absorption near-edge structure data reveal an ordered PEG assembly that helps protect the zerovalent Fe core.

Mechanistic and thermodynamic interpretations of zinc sorption onto ferrihydrite.

Elucidating the reaction mechanisms and estimating the associated transport and thermodynamic parameters are important for an accurate description of the fate of toxic metal pollutants, such as Zn(II), in soils and aquatic ecosystems rich in iron oxides. Consequently, sorption of Zn(II) ions onto ferrihydrite was investigated with macroscopic and spectroscopic studies as a function of pH (4.0-8.