(506b) Upcycling Waste PVC into Membranes: Evaluating the Potential Leaching of Hazardous Additives

Upcycling waste plastics into high-value membranes is a promising approach that enhances the sustainability of membrane fabrication while helping to mitigate plastic pollution by converting waste plastics into functional products. However, as many plastics contain plasticizers and additives from their initial production, the stability of these additives in upcycled membranes requires careful investigation due to potential health concerns. During the manufacturing of flexible PVC (F-PVC) pipes, various additives such as dioctyl phthalate (DOP), tribasic lead sulfide, and calcium carbonate are incorporated to enhance their flexibility, durability, strength, and workability. However, some of these additives, like DOP and tribasic lead sulfide, are potentially harmful chemicals. Therefore, a key concern in the upcycling process of F-PVC is the stability and leaching behavior of these additives during the process and later from the upcycled product (membrane), as this directly impacts the feasibility and safety of the entire upcycling process. In this study, a comprehensive investigation was conducted into the transport and leaching behavior of dioctyl phthalate (DOP) and tribasic lead sulfide during the upcycling of waste F-PVC into ultrafiltration (UF) membranes via the phase inversion process. The Hansen solubility parameters were employed to assess the potential interactions between PVC-DOP and various solvents and non-solvents in relation to DOP leaching. Furthermore, the stability and leaching of these additives from the upcycled F-PVC membranes under filtration conditions were evaluated, assessing both dynamic (1-month) and static (7-month) scenarios. The results revealed that DOP and tribasic lead sulfide did not leach out during the upcycling process including membrane synthesis and that the dynamic and static leaching of DOP from the F-PVC membranes was negligible, measuring less than 0.006 ppm while the dynamic and static leaching of lead from F-PVC membranes was also negligible measuring 0.01 ppb. These concentration levels were well below the limits set by the World Health Organization (WHO) and the United States Environmental Protection Agency (US EPA) for DOP and lead in drinking water. Additionally, the water permeability and dye rejection of the upcycled membranes remained consistent throughout the 1-month duration under a pressure of 100 psi, indicating stable membrane performance.