Background:

Specific superparamagnetic and paramagnetic particle systems form the basis for high-tech products. The properties and purity of such particle collectives are essential and quality-determining for the production and application of coatings, medical therapy or diagnostic systems, catalysts and electrochemical energy storage or electronic assemblies, e.g. in the field of battery technology. After particle production via synthesis or comminution, the particle systems used undergo a large number of process steps for quality adjustment. These steps include in particular fractionation, i.e. the selective separation of the particle system according to particle characteristics. Recycling technology also relies on such processes to extract special particles containing valuable materials from natural or secondary raw materials. The separation methods used so far lose efficiency and selectivity in the size range of ultrafine particle systems (50-1000 nm) because the complex superposition of the forces acting on the particles poses a challenge. The highly selective fractionation of magnetic nanoparticles on an industrial scale therefore remains a relevant research task.

Task:

The aim of the announced work is the investigation and development of fractionation processes of paramagnetic and superparamagnetic particle collectives on the basis of the separation characteristic of magnetic susceptibility. A magnetic field-controlled chromatography system developed at the institute is used as a fractionation method. The effect of an external magnetic field on the magnetisable separation matrix within the chromatography column strongly enhances the separation characteristic "particle susceptibility". After optimising the steel matrix used, material-specific fractionations in the particle size range of 50-1000 nm will be systematically investigated. Associated separation efficiencies will be tested for different types of paramagnetic nanoparticles mixed with diamagnetic SiO2 particles of the same size under variation of the operating parameters (flow velocity, field strength, particle concentration, pH, etc...).  The fractionation processes investigated will then be transferred to a continuous SMB chromatography system.