Complete Pb Recovery and Recycling from Perovskite Solar Cells Using Calcium Phosphate Nanomaterials
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김동회 세종대학교 Over the past 5 years, a significant amount of progress in perovskite solar cell field has been accomplished including high-performance, stability and large-area modules. Nevertheless, since Pb is an essential element in PSCs, environment, health, and safety (EHS) effects of materials and processes could be major concerns for PSC commercialization. Restriction of Hazardous Substances Directive (RoHS) considers that the treatment of Pb-contained nonaqueous solution waste occurred during manufacturing and the continuous exposure of Pb from waste or in the device could potentially cause long-term risks even at the low Pb levels as in the manufacturing process or device. CdTe solar cells have been commercialized, despite the presence of the hazardous element Cd, which is considered as an existing exemption-example of RoHS directive. There, Cd is controlled through a meticulous management and recycling program from production to disposal of CdTe thin-film solar cells. Thus, the development of a Pb removal/separation and recycling technology for Pb-containing nonaqueous polar aprotic solvent waste would address the EHS issues and would open the path to mass-production of PSCs. Although there have been several approaches to remove Pb from aqueous solution, such as chemical precipitation, membrane filtration, and adsorption using adsorbent particles. Because of precise Pb removal below ppm level, efficient, fast kinetics, the adsorption approach has been considered as one of the best methods to remove Pb ion from aqueous solvent. There are various adsorbent candidates with these required properties, e.g., TiO2, Fe2O3, carbon derivatives, and hydroxyapatite (Ca10(PO4)6(OH)2, HAP). Among these adsorbents, HAP has an advantage over its competitors like easily controllable particle size and shape, malleable surface charge by dopant, bio- and environmental-friendly and cost-effective earth-abundant components, and regenerative properties for better adsorbent. Moreover, controllable solubility and surface charge of HAP depending on pH makes possible to recycle Pb elements. The simple precipitation of PbI2 which is the main chemical for perovskite and has a very low solubility in water makes this recycling process feasible. Here, we report a sustainable Pb management process from the removal/separation of Pb in Pb-containing nonaqueous solvent for recycling of Pb raw materials as PbI2. The key to this process is the design of Metal-decorated HAP hollow composite (HAP/Metal), which serves two critical functions: (1) assigning magnetism for easy separation of Pb-adsorbed HAP/Metal composite from solvent, and (2) modifying surface charge to enhance Pb adsorption capability. We completed removing Pb from aprotic polar solvents below 15 ppb satisfying the standard from the United States Environmental Protection Agency (U.S. EPA). |