Silver recovery using electrochemically active magnetite coated carbon particles

• Magnetic carbon materials provided a sustainable silver recovery process.
• Magnetic hydrometallurgy can be performed for silver ions.
• Automated magnetic hydrometallurgy was demonstrated for silver recovery.

The electrochemical recovery of silver by employing recyclable superparamagnetic carbon materials (Cmag) is reported. The proposed strategy explores the adsorption properties and the large surface area of carbon, in conjunction with the superparamagnetic properties of magnetite nanoparticles, in order to collect Ag+ ions from the solution and to promove their rapid confinement at the working electrode surface, using an external magnet. Efficient electrodeposition can be performed in this way, facilitated by the preconcentration effect at the electrode. The adsorption process at the magnetic carbon particles proceeds according to the Langmuir model, exhibiting an adsorption capability of 61.5 mg of silver per gram of Cmag. As a proof of concept, an automated system was specially designed for performing successive batch cycles, encompassing the capture, transport, confinement, electrodepositon of silver, and recycling of the magnetite coated carbon particles from the electrode. The recovery process was successfully demonstrated in this work, by processing discarded X-ray photographic films.

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