Urs A. Peuker

Characterization of magnetic ion-exchange composites for protein separation from biosuspensions

Downstream processing is a major issue in biotechnological production. A multitude of unit operations with nonsatisfying yield are often used to reach the desired product purity. Direct recovery technologies such as high-gradient magnetic fishing (HGMF) are advantageous because of their ability to separate the desired product in early stages from crude cultivation broths. However, the use of magnetic particles to capture valuable biotechnological products is often linked to the drawback that support particles are expensive and not available in greater quantities. This current work presents new composite magnetic particles that can be used in biotechnology. They are manufactured by a spray drying process. During this process, the nanosized magnetite particles as well as functional ion-exchange nanoparticles are integrated into one particle in which they are linked by a matrix polymer. The production procedure is flexible, scalable, and therefore economical. These particles have good adsorption capacities of up to 85 mg/g adsorbed protein and good binding kinetics. They are resistant to harsh conditions such as short ultrasonic treatment or extreme pHs. In order to test their usefulness in biosuspensions, model proteins were separated using these particles. The anion and cation exchanger particles separated lysozyme (LZ) or BSA from cultivation suspensions. The selectivity of recovery was dependent on other proteins present as is usual for ion-exchange binding mechanisms.

Nanocomposites based on technical polymers and sterically functionalized soft magnetic magnetite nanoparticles: synthesis, processing, and characterization

This experimental study deals with the synthesis, processing, and characterization of highly filled nanocomposites based on polyvinyl butyral/magnetite (PVB/Fe3O4) and polymethylmethacrylate/magnetite (PMMA/Fe3O4). The nanoparticles are synthesized in an aqueous coprecipitation reaction and show a single particle diameter of approximately 15 nm. The particles are sterically functionalized and covered by PVB and PMMAin a spray drying process. The synthesized compound particles are further processed by injection molding to test specimens with filler contents up to 14.5 vol.-%. PVB and PMMA specimen are processed as a reference as well. The distribution of the nanoparticles is characterized by microscopy. Besides a minor number of agglomerates and aggregates the nanoparticles are distributed homogeneously in the PVB composites. Furthermore, the injection molded specimens are characterized with regard to their thermal degradation, polymer structure, and their mechanical and magnetic properties. The presence of nanoparticles capped with ricinoleic acid shows significant decrease in degradation temperature and in glass transition temperature of PVB. The degradation temperature of PMMA is increased by adding nanoparticles capped with oleic acid. Dynamic-mechanical properties as well as the magnetic permeability of PVB and PMMA are improved significantly by adding nanoparticles.

Characterization of protein capacity of nanocation exchanger particles as filling material for functional magnetic beads for bioseparation purposes.

In this study we describe the synthesis and characterization of nanocation exchanger particles (NCEX) as the functional filling material for magnetic beads. Polystyrene NCEX particles were synthesized from styrene via a miniemulsion polymerization. The coupling of cation exchanger groups was done with chlorosulfuric acid after the polymerization reaction. The NCEX particles have an average diameter of 160–260 nm. Their ion exchange capacity amounts up to 4.58 mval/g. In an adsorption experiment it was possible to adsorb 192 mg lysozyme/g NCEX. Depending on the equilibrium concentration of lysozyme in the bulk solution 70–85% of the attached protein was desorbed. NCEX particles were used to produce magnetic beads with cation exchanger properties. Therefore an innovative production process for the synthesis of magnetic beads from different single components was used. The produced magnetic beads contained 40 wt % NCEX material and showed an ion exchanger capacity of 2 mequiv/g. It was possible to adsorb 75 mg lysozyme/g magnetic beads with a maximum recovery rate of 95%.

Coagulation and stabilization of sterically functionalized magnetite nanoparticles in an organic solvent with different technical polymers

This experimental study deals with the colloidal stability of sterically functionalized magnetite nanoparticles in a low dielectric constant organic solvent with different concentrations of technical grade polymers. Those dispersions are the starting point of a solution and spray drying process chain to synthesize highly filled nanocomposite materials with nanoparticle volume concentrations exceeding 10%. We introduce a thermo gravimetric method together with light extinction and dynamic light scattering measurements to gain quantitative information on the concentration of primary particles and the mechanism of destabilization or stabilization by polymer addition. Poly(vinyl butyral) is found to stabilize the dispersion considerably caused by stronger interactions with the fatty acid coated magnetite particles quantified by means of adsorption measurements. Both poly(methyl methacrylate) as well as two grades of poly(bisphenol A carbonate) are found to destabilize the dispersion due to depletion flocculation over the entire concentration range investigated However there is a significant quantity of a stable fraction of primary nanoparticles in the supernatant after depletion flocculation occurred. This fraction of primary particles is increasing with decreasing polymer concentration. We furthermore point out important concerns and limitations for the composition of and concentrations in such complex colloidal systems for use in industrially relevant processes.

Liquid-Liquid Interfacial Transport of Nanoparticles

The study presents the transfer of nanoparticles from the aqueous phase to the second nonmiscible nonaqueous liquid phase. The transfer is based on the sedimentation of the dispersed particles through a liquid-liquid interface. First, the colloidal aqueous dispersion is destabilised to flocculate the particles. The agglomeration is reversible and the flocs are large enough to sediment in a centrifugal field. The aqueous dispersion is laminated above the receiving organic liquid phase. When the particles start to penetrate into the liquid-liquid interface, the particle surface is covered with the stabilising surfactant. The sorption of the surfactant onto the surface of the primary particles leads to the disintegration of the flocs. This phase transfer process allows for a very low surfactant concentration within the receiving organic liquid, which is important for further application, that is, synthesis for polymer-nanocomposite materials. Furthermore, the phase transfer of the nanoparticles shows a high efficiency up to 100% yield. The particle size within the organosol corresponds to the primary particle size of the nanoparticles.

Nanoparticles in Organic Solvents with Polymers – Stability and Consequences upon Material Synthesis through Spray Drying and Melt Moulding

It is a well accepted fact that nanoparticles and their industrial and commercial use have the potential to improve properties of modern materials substantially. Especially polymeric materials are attractive for incorporating nanoparticles with special properties only apparent in the nanoscale. One main consideration in processing such composite materials is to prevent the nanoparticles from agglomerating or even worse aggregating. In this paper a modular process method is presented based on a mixture of sterically stabilized nanoparticles in an organic solvent with soluble polymers and subsequent spray drying to quickly yet thermally carefully remove the solvent. The method has the potential for large scale production of highly filled nanoparticle-polymer-composites. However the bottleneck of this method is the unknown interaction of polymers and stabilized nanoparticles. We present the impact of depletion flocculation and subsequent phase separation or stabilization by adsorbing polymers on the dispersion of the nanoparticles. It is shown that the processing method is more adequate when compared to traditional melt moulding. The best magnetite nanoparticle stability in dichloromethane is achieved using ricinoleic acid. Besides flocculates we can identify separate primary particles in the composite. The size of the floccules is in the lower micrometer range for nanoparticles 15 nm in size.

Prediction of silo-vibrations using a modified lambdameter

Predicting silo-vibrations is not yet universally possible but only to a very limited extent. A mechanism of excitation of silo vibrations can be found in oscillating shear stresses between the bulk solid and the inner silo wall, the so-called “wall-stick-slip” effect. So if this wall-stick-slip occurs during shear experiments in shear testers, the probability of silo-vibrations in silos will be high. However if there is no slip-stick effect observed, this will not consequently exclude silo-vibrations. The influences on a stable stick-slip were studied in wall friction experiments with a rotational shear tester and in a specially developed silo model based on a lambdameter. The examined parameters are normal stress, shear velocity, wall roughness and particle shape. Plastic pellets which are known to honk (PET, PA) and plastic pellets that do not honk (PE) are considered [1]. It is shown that the silo model based on a lambdameter is more suitable for initiation and measurement of stable wall-stick-slip of...

Note: Production of stable colloidal probes for high-temperature atomic force microscopy applications

For the application of colloidal probe atomic force microscopy at high temperatures (>500 K), stable colloidal probe cantilevers are essential. In this study, two new methods for gluing alumina particles onto temperature stable cantilevers are presented and compared with an existing method for borosilicate particles at elevated temperatures as well as with cp-cantilevers prepared with epoxy resin at room temperature. The durability of the fixing of the particle is quantified with a test method applying high shear forces. The force is calculated with a mechanical model considering both the bending as well as the torsion on the colloidal probe.

Zur mechanischen Aufbereitung von Li-Ionen-Batterien

ZusammenfassungDie TU Bergakademie Freiberg/Sachsen hat ein auf überwiegend mechanischen Prozessen basierendes Verfahren zur Aufbereitung von Li-Ionen-Batterien aus Elektroautos entwickelt, mit dem nach vorhergehenden sicherheitsrelevanten Schritten (Demontage und Entladung) zukünftig eine Alternative bzw. Ergänzung zu den bestehenden energieintensiven pyro- und hydrometallurgischen Prozessen existiert. Die Robustheit des Verfahrens wurde für Akku-Typen unterschiedlicher Zusammensetzung erfolgreich erprobt. Auch für den Sonderfall der Li-Ionen-Starterbatterien wurde die Prozessfähigkeit nach entsprechender Anpassung der Parameter nachgewiesen. Der Bau einer Pilotanlage befindet sich bereits in der Projektierungsphase.AbstractIn the last four years Technical University Freiberg/Sachsen has developed a process for the mechanical recycling of Li-ion batteries from electric vehicles. After solving some safety-relevant issues (dismantling and discharging) the process offers an alternative or addition to existing energy-intensive pyro- and hydrometallurgical processes. Robustness of the process was verified for several battery types of divergent material compositions. The process capability was verified also for Li-ion starter batteries, provided that relevant parameters were adjusted. A pilot-plant is in planning.

Milling Result Prediction

Fine grained ore can only be exploited with finer milling, which results in additional milling costs. The ability to infer the optimal milling parameters and corresponding grades of recovery from microstructural information allows optimal extraction and predicting processing costs and final recovery. The MLA (Mineral Liberation Analyzer) allows the 2D size of grains in the ore to be quantified. We have developed a method to predict the 3D liberation of the value mineral in the ore from a combination of milling experiments and MLA images.