Microfluidic experiments on enrichment of paramagnetic metal ions in aqueous solutions by applying inhomogeneous magnetic fields


Microfluidic experiments on enrichment of paramagnetic metal ions in aqueous solutions by applying inhomogeneous magnetic fields

Mutschke, G.; Yang, X.; Wojnicki, M.; Femerling, M.; Zabinski, P.

Magnetic separation is a well-established technology for separating magnetic particles from solutions. The magnetic gradient force scales with the magnetization density and the volume of the particle. The magnetic moment of paramagnetic metal ions in solution could be utilized as well for separating ions from solutions in strong magnetic fields of large spatial gradients. This idea dates back to early work of Noddack et al [1], where firstly separation effects were found for rare earth metal ions in aqueous solutions. However, the effect is limited, as the ratio of magnetic to thermal energy is small. Recently, distinct separation effects of paramagnetic ions in inhomogeneous magnetic fields were reported in gel [2] and in various aqueous solutions [3,4,5].
Triggered by these findings, microfluidic experiments were performed. The setup consists of a small reactor printed by 3D technology where a spiral pipe flow is exposed to an inhomogeneous magnetic field created by an iron wire, the spiral of which is close to the pipe, and which is magnetized in an external magnetic field, thus creating strong gradients near the pipe. Flow experiments were performed for different salt solutions. At the outflow, the flow volume was separated into a near-magnet and a far-magnet half, the concentrations of which were analyzed by UV/VIS spectrophotometry and by ICP-MS. The absorption spectrum of 0.1 M HoCl3 solution is shown in Fig.1. According to Beer-Lambert's law, the absorbance in selected peaks can be used as a measure of the ion concentration. The concentration difference from the two outlets of the reactor was measured, and the effects of the magnetic field gradient and the flow rate were studied.
Acknowledgement:
This work is supported by the German Federal Ministry of Education and Research, Grant No. 01DS16007.
References
[1] Noddack, W., Noddack, I. and Wicht, E., Berichte der Bunsengesellschaft für physikalische Chemie 62 (1958): 77-85.
[2] Franczak, A., Binnemans, K., & Fransaer, J., Phys. Chem. Chem. Phys. 18 (2016): 27342-27350.
[3] Kolczyk, K., Kutyla, D., Wojnicki, M., Cristofolini, A., Kowalik, R., & Zabinski, P., Magnetohydrodynamics 52 (2016): 541-547.
[4] Yang, X., Tschulik, K., Uhlemann, M., Odenbach, S., & Eckert, K., J. Phys. Chem. Lett. 3 (2012): 3559-3564.
[5] Bing, J., Ping, W., Han, R., Shiping, Z., Abdul, R., & Li, W., Chin. Phys. B 25 (2016) 074704.

  • Lecture (Conference)
    68th Annual Meeting of the International Society of Electrochemistry, 27.08.-01.09.2017, Providence, RI, USA

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