Magnetic separation of iron and heavy metals from water.

A magnetic separation device is being developed for removal of iron and heavy metals from water. The device consists of a column of supported magnetite surrounded by a movable permanent magnet. The mineral magnetite, or synthetically prepared iron ferrite (FeO x Fe2O3), is typically supported on various materials to permit adequate water passage through the column. In the presence of an external magnetic field, enhanced capacity was observed in using supported magnetite for removal of actinides and heavy metals from wastewater. The enhanced capacity is primarily due to magnetic filtration of colloidal and nanoscale particles along with some complex and ion exchange sorption mechanisms. This paper will review some previous work on the use of magnetite for wastewater treatment and discuss the development and potential of the magnetic nanoscale filtration/sorption process for water treatment. Recent research results are also presented on preliminary experimental studies using the process with water samples containing iron.

Flow-through sequential extraction approach developed from a batch extraction method.

Sequential extractions of contaminants from a soil or sediment have been shown to be cost-effective contaminated site assessment tools that provide information on contaminant partitioning within an environmental matrix. Such information is necessary for defining remediation alternatives and mitigation strategies. The typical sequential extraction approach involves a batch method, and known limitations include the possibility of contaminant readsorption to the remaining soil or sediment In this work, a flow-through reactor was constructed and tested for application in a sequential extraction scheme. The sequential extraction scheme used was one developed for actinide-contaminated materials. The flow-through approach gave partitioning results that were similar to the batch method for uranium. We also monitored the extraction of stable Ca, K, Fe, Al, Zr, and Sc and obtained partitioning results generally similar to those observed with the batch extraction, except for Ca. Our results indicate readsorption of Ca when using a batch approach is small but significant and is eliminated with our new flow-through method. A limitation of the flow-through method is the possibility of underextraction of certain phases and higher analytical uncertainties. These uncertainties are more difficult to minimize, as compared to the uncertainty obtained with a batch approach.

Ion-pair extraction of Co(II) by crown ethers from perchlorate medium.

The extraction of cobalt(II) by chloroform solutions of the crown ethers (CE) 12C4, I5C5, 18C6, Dbl8C6, Dchl8C6 or Dch24C8 from aqueous perchlorate medium was investigated. Slope analysis of the experimental data suggested that the extraction of Co(II) by these CEs takes place through ion-pair formation, and that the chemical formula of the main extracted species is Co(OH)(+)ClO(-)(4).CE. The magnitudes of the extraction constants are in the sequence 18C6 > Dch18C6 > Dch24C8 > Db18C6 > 15C5 > 12C4, which is discussed in terms of the correspondence between the CE cavity size and the ionic radius of cobalt(II).