The remediation of water sources contaminated with toxic heavy metal ions and micropollutants has become a critical field of environmental chemistry research. Some of the most widely-reported contamination include dangerous levels of lead and cadmium, which are linked to widespread long-term organ damage. To this end, advanced purification techniques have been developed to provide clean drinking water supplies, including the use of adsorptive materials which provide low-energy separations. These materials can be applied to large-scale separations using advanced fabrication techniques such as the self-assembly and non-solvent induced phase separation (SNIPS) method of casting. In this work, the block polymer material polyisoprene-b-polystyrene-b-poly(N,N-dimethylacrylamide) (PI-PS-PDMA) was cast into nanoporous membranes via the SNIPS method. After hydrolysis of the pore-lining PDMA block to poly(acrylic acid) (PAA), the walls of the nanopores can be further reacted to a variety of functional moieties via simple coupling reactions. Here, the pores were tailored for heavy metal ion separations by functionalization with either the naturally-occurring peptide glutathione, which limits metal toxicity in organisms, or its simplified analog, cysteamine. Characterization via Fourier transform infrared spectroscopy and scanning electron microscopy confirmed conversion of functional groups and preservation of the self-assembled nanostructure at the membrane surface. Metal ion adsorption studies on by the functionalized membranes indicated saturation capacities of 1.4 and 1.6 mmol g-1 membrane for lead and cadmium ions, respectively, nearly matching the highest reported values in the literature. The experimentally-determined capacities allowed for the accurate prediction of metal ion removal in static adsorption experiments at low concentration conditions. Furthermore, utilizing the membrane as a flow-through adsorber allowed for the ion removal to exceed 98% of the lead ions fed. Adsorption experiments in the presence of competing cations showed no noticeable decrease in purification performance. Finally, the captured heavy metal ions could be released by a pH swing, regenerating the binding sites in the membrane, which maintained its high binding capacity upon repeated loading cycles.

Bio-inspired membranes from block polymer precursors for remediation of heavy metal contaminated water sources

254th National Meeting (2017)

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