Towards a Circular Economy in Electroless Pore-Plated Pd/PSS Composite Membranes: Pd Recovery and Porous Support Reuse

Abstract

The recycling of a planar composite Pd membrane over a porous stainless-steel support modified with a CeO2 interlayer (Pd/CeO2/PSS) was investigated using a leaching-based recycling strategy to recover palladium while maintaining the support's structural integrity. The membrane was prepared by a continuous flowing electroless pore-plating method (cf-ELP-PP) previously developed by our group. A series of experiments was conducted to evaluate the effect of leaching conditions-temperature, acid concentration, and duration-on Pd extraction and support preservation. Nitric acid (HNO3) was used as the leaching agent, and the condition of 30 vol.% HNO3 at 35 degrees C for 24 h was found to enable complete Pd recovery with limited dissolution of metals from the support. The regenerated supports exhibited an Fe-Cr oxide layer and part of the CeO2 interface, allowing the elimination of cleaning and calcination steps in the membrane reprocessing workflow. A new Pd-CeO2 interfacial layer was applied, followed by Pd redeposition via cf-ELP-PP. The resulting recycled membrane exhibited a homogeneous and defect-free Pd layer, with hydrogen permeation performance comparable to that of membranes fabricated on fresh supports. These results demonstrate that Pd membranes can be successfully fabricated on recycled 316L stainless-steel substrates, supporting the viability of this approach for material reuse in membrane technology.