Arlt, C. / Brekel, D. / Franzreb, M. (2020) 

Separation and Purification Technology, 2021, 259, 118123

Abstract

The production of high-quality and pure nanoparticles is becoming increasingly important from an industrial perspective. Current and emerging applications of high-quality nanoparticles include among others medical uses, analytical products or functional pigments. Often the initial synthesis does not deliver the required quality with respect to uniform size and composition, resulting in the need of additional purification and fractionation steps. However, technical fractionation of nanoparticles is still a challenge, especially if looking for continuous processes. If the impurities are within a similar size range than the target particles, classical processes, such as filtration, are often not suitable. In this study a novel and easily scalable system is presented, which can continuously fractionate nanoparticles by their magnetic properties. The system is based on the principle of magnetic chromatography, which allows to control the interaction between nanoparticles and a magnetizable stationary phase by means of an external magnetic field. Running a single chromatography column in pulse mode for the fractionation of diamagnetic and superparamagnetic nanoparticles, peak resolutions of the separated particle fractions of 0.93 could be achieved. Continuous operation could be realized by transferring the principle into a simulated moving bed system including four columns. This allowed continuous feed streams of nanoparticles with a space time yield of 27.5 mg/(L·min) to be fractionated. Recovery rates of up to 98% were achieved, while the contaminant depletion up to 100% could be accomplished. Based on these results we see our process as a potential alternative to demanding and expensive nanoparticle fractionation methods, such as ultracentrifuges, requiring less energy and including no quickly rotating parts.

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