Stability assessment of layer-by-layer nanofiltration membranes for element recovery from highly acidic media

Abstract

The recovery of critical raw materials such as indium (In) and silver (Ag) from end-of-life thin-film photovoltaics is essential for supporting the growing demand for renewable energy technologies. This study evaluates the acid stability of layer-by-layer nanofiltration (LbL-NF) membranes for metal recovery from acidic leachates to identify a sustainable alternative to conventional methods. Among various configurations, sPES(PAH/PSS)₄ membranes exhibited outstanding resistance and long-term stability (> 300 h) in 5 % HNO₃, which potentially enables the recovery of 9100 g In and 6600 g Ag per m² of membrane. A life cycle assessment indicated a 34 %–46 % reduction in the global warming potential (GWP) of recycled Ag and a 40 %–50 % reduction for recycled In compared with the supply mix under modelled conditions. For Ag, the GWP was 137 g and 123 g CO₂-eq/g at 70 % and 80 % LbL-NF permeate recovery, respectively. For In, the GWP was 50 g and 55 g CO₂-eq/g at 70 % and 80 % recovery, respectively. These results highlight the climate benefits of LbL-NF membranes in circular resource recovery from end-of-life photovoltaics, which helps to identify key hotspots for optimisation and scale-up.