title: Multi-objective optimization of chromatographic rare earth element separation.
abstract: The importance of rare earth elements in modern technological industry grows, and as a result the interest for developing separation processes increases. This work is a part of developing chromatography as a rare earth element processing method. Process optimization is an important step in process development, and there are several competing objectives that need to be considered in a chromatographic separation process. Most studies are limited to evaluating the two competing objectives productivity and yield, and studies of scenarios with tri-objective optimizations are scarce. Tri-objective optimizations are much needed when evaluating the chromatographic separation of rare earth elements due to the importance of product pool concentration along with productivity and yield as process objectives. In this work, a multi-objective optimization strategy considering productivity, yield and pool concentration is proposed. This was carried out in the frame of a model based optimization study on a batch chromatography separation of the rare earth elements samarium, europium and gadolinium. The findings from the multi-objective optimization were used to provide with a general strategy for achieving desirable operation points, resulting in a productivity ranging between 0.61 and 0.75 kgEu/mcolumn(3), h(-1) and a pool concentration between 0.52 and 0.79 kgEu/m(3), while maintaining a purity above 99% and never falling below an 80% yield for the main target component europium.
authors.affiliation: Department of Chemical Engineering, Centre for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
authors.forename: Hans-Kristian
authors.initials: HK
authors.lastname: Knutson
authors.affiliation: Department of Chemical Engineering, Centre for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Holmqvist
authors.affiliation: Department of Chemical Engineering, Centre for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden. Electronic address: Bernt.Nilsson@chemeng.lth.se.
authors.forename: Bernt
authors.initials: B
authors.lastname: Nilsson
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000592:standards*; D005063:Europium / Q000302:isolation & purification*; D005682:Gadolinium / Q000302:isolation & purification*; D013058:Mass Spectrometry; D012493:Samarium / Q000302:isolation & purification*
chemical_list: D012493:Samarium; D005063:Europium; D005682:Gadolinium
keywords: Chromatography; Multi-objective optimization; Parameter estimation; Pareto optimal surface; Rare earth elements