Sustainable synthesis of functional zeolites from waste OLED powder for heavy metal adsorption and barium immobilization

Abstract

This study explores the synthesis of zeolite from waste organic light-emitting diode (OLED) powder using a hydrothermal method and evaluates its potential application for heavy metal adsorption and harmful ion immobilization. OLED-based zeolites were produced by aging a mixture of waste OLED powder and NaOH at 100 °C for varying durations (3, 6, 12, 24, and 72 h). Structural evolution and functional performance were assessed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), N<inf>2</inf> adsorption–desorption, inductively coupled plasma optical emission spectroscopy (ICP-OES), and batch adsorption tests for lead (Pb2+). The synthesized zeolites exhibited the formation of Na-P1, chabazite, harmotome, and albite phases with increasing aging time, accompanied by pore refinement and increased surface area. The content of Na-P1 zeolite increased with aging time, but the rate of increase progressively declined, approaching a saturation level at approximately 24 h. In contrast, albite exhibited a nearly linear increase, with its content being proportional to the aging duration. Ba2+ ions were initially released into the alkaline solution but progressively decreased over time, indicating immobilization within the crystalline matrix, as supported by the formation of Ba-containing phases (e.g., harmotome) and SEM/EDS elemental mapping. In addition, the OLED-based zeolites demonstrated significantly enhanced Pb2+ adsorption performance with aging time, attributed to enhanced crystallinity and mesoporous structure and the overall adsorption performance was predominantly controlled by the abundance of Na-P1 zeolite, highlighting its crucial role in determining the material’s uptake capacity. These findings demonstrate the potential of converting electronic waste into functional zeolites with dual capabilities of toxic ion immobilization and environmental remediation, contributing to sustainable and high-value-added resource utilization. © 2025 The Korean Society of Industrial and Engineering Chemistry.