Applied colloidal aggregation: Separation of fine polymer particles from dilute suspensions by magnetic seeded filtration (Microplastics)

F. Rhein*, H. Nirschl, Karlsruhe Institute of Technology (KIT), Germany

Microplastics are nowadays a highly discussed topic: Whether through the decomposition of larger plastic waste or direct usage on a small particle scale, microplastics find their way into the natural ecosystem with still not fully understood consequences. This work investigates the separation of such contamination by magnetic seeded filtration on a laboratory scale and thus discusses an application example for the often theory-focused colloidal aggregation process. Magnetic seeded filtration consists of two steps: Firstly, fine paramagnetic particles are agglomerated with magnetic particles and secondly, these hetero-agglomerates are removed from the suspension by high gradient magnetic separation.

In the scope of this work, it could be shown that it is possible to reach high separation efficiencies of up to 10-2 vol%. Furthermore, a thorough parameter study identified the electrostatic interaction to be of dominating importance: Especially the pH value regulating the surface charge of the particles effects the process results dramatically. However, even with non-optimal pH setting resulting in repulsive surface charges, an agglomeration could be forced by the adjustment of the ionic strength. In addition, this work gives insight into the agglomeration kinetics: Time dependent separation efficiencies are measured and were able to be described by simplifying mathematical models. Thus, the process is opened up for further optimization, as process time and result can be balanced in a profound manner.

This presentation gives insight into the applicability of magnetic seeded filtration in general and offers operational guidelines that improve process results. Furthermore, the obstacles and major concerns for a large-scale implementation are discussed...

Session: L8 - Short Oral Presentations
Day: 23 October 2019
Time: 14:45 - 16:00 h

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