Reversible microfluidics device for precious metal electrodepositionand depletion yield studies

• Published in: Electrochimica acta
• Main Authors: Gouyon, Jérémie, Simon, Craig, Griveau, Sophie, Sella, Catherine, Thouin, Laurent, Bedioui, Fethi, Varenne, Anne
• Format: Journal Article
• Language: English
• Published: Elsevier 22.05.2020
• Subjects: Analytical chemistry; Chemical Sciences; or physical chemistry; Theoretical and; Precious metals; Depletion; Electrodeposition; Microfluidics
• ISSN: 0013-4686
• DOI: 10.1016/j.elecom.2017.05.013

A new low-cost reversible Glass-NOA®-PDMS microfluidic device was designed for the study of recoveryyield of precious metals present in acid media mimicking leach liquors for long-term recycling objectives.It offers the unique advantage of allowing easy washing of the microchannel and renewal of the electrodesurface by simply repositioning the microband electrodes which allows this type of device to have arelatively much longer lifespan than irreversibly closed ones. It consists in a re-useable microchip withfour graphite microbands electrodes, prepared by screen printing, to set-up an original amperometricdevice for both depletion and yield quantification. One upstream working electrode is devoted to thedepletion of the metallic ions through their electrolysis by electrodeposition while the second downstreamworking microelectrode is used as real-time detection electrode to evaluate the depletion efficiency.The dimensions of the depletion electrode and of the channel were optimized thanks tonumerical simulations for a given range of flow velocities. First, the performances of the device wereassessed experimentally according to flow rate and applied potential under continuous flow, and thencompared to theoretical predictions using an electrochemical probe, ferrocenemethanol. The proof ofconcept was then demonstrated for precious metal, by electroreduction of Pd(II) and Au(III) from acidicleach liquors under continuous flow, with a depletion yield of up to 89% and 71% respectively.