(619d) Development of Multifunctional Membranes for Efficient Heavy Metal Ion Capture and Detection

Water pollution caused as a result of heavy metal ions is a major environmental and health concern. This study reports the development of adsorptive membranes with a high density of binding sites for efficient metal ion capture and detection. The membranes are based on a newly-synthesized reactive polymer with a polysulfone (PSf)-like backbone, which can be transformed into porous membranes using a surface-segregation-vapor-induced phase separation (SVIPS) method. After dissolving the polymer to form a homogenous casting solution, the solution was drawn into a thin film on a non-woven polyester substrate using a doctor’s blade. This process occurs within a humid (95-99% humidity) chamber such that water vapor, a non-solvent, permeates into the film of casting solution and initiates phase separation. Controlling the nonsolvent (water) vapor intrusion time allowed the membrane to form different morphology, and a water bath was later applied to solidify the membrane structure. During the process, the hydrophobic backbone of the polymer forms the solid matrix of the porous membrane, while the hydrophilic reactive moieties preferred to interact with the water molecules and be exposed along the pore walls. The density of the surface binding sites was measured by copper ion adsorption tests. The experimentally measured saturation capacity showed excellent performance compared to prior membranes made using blends of PSf and polystyrene-block-polyacrylic acid (PS-b-PAA) copolymers. Furthermore, the experimental capacity was consistent with the polymer composition indicating that most of the pendant reactive moieties segregated to the surface of the membrane pores. Characterization techniques such as permeability tests and SEM images were also used to appraise the membrane structure and performance. Lastly, due to the nature of the reactive polymer, the surface chemistry of the membranes could be patterned. The patterned membrane exhibited rapid detection of mixed ion systems using a dual-ligand approach. Furthermore, the patterned membrane can be reused by concentrated hydrochloric acid.