SORPTION CAPACITY OF FERROMAGNETIC MICROPARTICLES COATED WITH CMPO

Magnetically assisted chemical separation (MACS) was developed at Argo nne National Laboratory as a compact process for reducing the volume o f high-level aqueous waste streams that exist at many U.S. Department of Energy sites. In the MACS process, ferromagnetic particles coated w ith solvent extractants are used to selectively separate transuranic n uclides and heavy metals from aqueous wastes. The contaminant-loaded p articles are recovered from the waste stream by using a magnet. For th e recovery of transuranic species the extractant used is tyl(phenyl)-N ,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) dissolved in tri-n- butyl phosphate (TBP). To better understand the extraction chemistry o f this solvent/particle system, europium was used to monitor the sorpt ion capacity of the MACS particles for lanthanides and actinides. Euro pium concentrations varying from 10(-7)(M) under bar to 10(-1)(M) unde r bar were prepared with 3 (M) under bar NaNO3 in 0.1 (M) under bar HN O3. Neutron activation analysis was used to measure the concentration of europium. The sorption capacity was evaluated, along with the sorpt ion isotherms to simulate multiple contact stages. The maximum absorpt ion capacities obtained was 0.62 mmol/g. The adsorption models of Lang muir and Freundlich and the extended Langmuir model of Brunauer, Emmet t, and Teller (BET) were fitted to the data. The best correlations wer e obtained from the Langmuir and BET models, a result that supports a monolayer adsorption mechanism. The Langmuir and BET models suggested a loading capacity of 0.33 mmol/g and 0.25 mmol/g, respectively. The F reundlich model results support favorable metal loading with a 1/n val ue of 0.3.