A closed-cycle and low-cost strategy for recovery and reuse of toxic lead from discarded perovskite photocatalysts.

Lead halide perovskites are promising photocatalysts, while high toxicity of lead results in challenging post-treatment. In this paper, an ion exchange-directional precipitation strategy is developed to recycle and reuse lead as PbBr2. CsPbBr3 perovskite-based catalysts are dissolved to produce Cs+ , Pb2+ and Br- ions, with Cs+ and Pb2+ extracted via multiple adsorption cycles using cation exchange resin. Gradient HNO3 solutions are used to elute the resin to maximize release of metal ions. The released Pb2+ is directionally precipitated as Pb(OH)2 through pH adjustment, followed by dissolving in HNO3 solution to obtain pure Pb2+ solution. After reaction with Br-, Pb2+ converts into highly purified PbBr2, with 92.06 % of lead recovery efficiency from perovskite catalysts. More importantly, the recycled PbBr2 is successfully reused to synthesize CsPbBr3-based catalysts, forming a closed-cycle and low-cost strategy for recovery and reuse of toxic lead. R-CsPbBr3-1 and R-CsPbBr3/BiOBr-1 achieves ethanol yields of 32.77 and 51.65 μmol‧g-1‧h-1, respectively. After five recovery and reuse cycles, ethanol production rates of R-CsPbBr3-5 and R-CsPbBr3/BiOBr-5 retain 31.80 and 45.40 μmol‧g-1‧h-1, maintaining 94.56 % and 83.12 % of the catalysts synthesized from commercial PbBr2, respectively. Furthermore, material reuse reduces costs by 73.01 %, demonstrating an efficient, low-cost, eco-friendly strategy for perovskite lead recycling.