(153d) Intensification of Reaction-Diffusion Processes By Magnetic Nanomixing

Zadražil, A., University of Chemistry and Technology in Prague
Št?pánek, F., University of Chemistry and Technology Prague
Snita, D., Institute of Chemical Technology, Prague
Intensification of reaction-diffusion processes by magnetic nanomixing

The ability to control the spatial distribution of concentration in a chemical process is a fundamental requisite for the safe, reliable, economically feasible and environmentally benign operation of most technologies that provide the material basis on which the world depends. The industrial production of everyday materials and commodities such as medicines, cosmetics or electronics would not be possible without effective mixing. The processes that occur in living organisms at both tissue and cell level are also crucially dependent on the local rate of convection and diffusion transport. The influencing of the local diffusion rates or other process parameters that depend on diffusion such as inter-phase mass transfer and reaction kinetics in both chemical and biological systems are also of key interest.

In this study, we are investigating the increase of the local diffusion coefficient by low-frequency magnetic field stimulation of magnetic nanoparticles (magnetic nanomixing). For the creation of a sinusoidal magnetic field, an air-cooled solenoid was fabricated from a broken ferrite ring (gap diameter – 4 mm). We were able to obtain magnetization up to 30 mT at 10,000 Hz. The diffusion rate of a model dye (carboxyfluorescein) in a thin square capillary (2 mm in diameter) was used to evaluate the effect of magnetic nanomixing. The capillary was filled with a solution of dextran-coated magnetic nanoparticles (concentration less than 0.1mg/ml), and 20 ml of carboxyfluorescein was placed in one end. The flow of the aqueous environment due to the concentration gradient or mechanical perturbations was suppressed either by increasing its viscosity (addition of starch) or by immobilization by an agar gel. The capillary was illuminated by a UV-light (390 - 400 nm Dino-Lite microscope) at which the carboxyfluorescein emits green light. The obtained images were evaluated by image analysis (software ImageJ) to get space- and time-dependent concentration profiles of the model dye. The diffusion coefficient was evaluated from this dependency using the Fick’s second law. The effect of magnetic particles concentration, magnetic field strength and frequency on the diffusion rate enhancement was experimentally investigated.