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

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 °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.