Tailored MoS2/PEI-coated ceramic nanofiltration membranes for treating wastewater from 3D NAND flash memory manufacturing

Abstract

The rapid expansion of 3D NAND flash memory manufacturing has generated wastewater streams containing persistent inorganic pollutants, particularly dissolved silica (Si(OH)(4)) and ammonium phosphate ((NH4)(3)PO4), which are difficult to remove due to their low molecular weight and chemical stability. In this study, molybdenum disulfide (MoS2)-coated ceramic nanofiltration (NF) membranes incorporating polyethyleneimine (PEI) were developed to regulate surface charge, enhance interfacial adhesion, and control effective pore size. The effects of MoS2-to-PEI weight ratio (1:1, 2:1, and 4:1) and MoS2/PEI coating density (2.0-3.0 mg/cm(2)) were systematically investigated to elucidate their roles in membrane structure and separation performance. PEI incorporation promoted the formation of a uniform, compact, and highly functionalized selective layer, resulting in significantly enhanced rejection compared to pristine ceramic and MoS2-only membranes. Optimal performance was achieved at a MoS2-to-PEI ratio of 2:1 and a coating density of 2.0 mg/cm(2), forming an ultrathin selective layer (similar to 3.2 mu m) and achieving 60.1% rejection of Si(OH)(4) and 22.7% rejection of (NH4)(3)PO4. The results demonstrate that controlled tuning of coating composition and density governs pore structure and charge-based selectivity in ceramic NF membranes. This study provides design insights for treating semiconductor wastewater under chemically demanding conditions.