(408a) High-capacity adsorbents with hierarchical structures printed from polymer composites

The increasing global population, improved standards of living, and the expansion of irrigated agriculture will make meeting the demand for fresh water a challenge. Selective adsorbents that target the capture of contaminants are one technology for helping to ensure a supply of water that is fit for its intended use. Adsorbent design has focused largely on the development of novel chemistries. However, while there is scope for improvements in materials properties, process analysis suggests that corresponding efforts need to be dedicated to addressing limitations at the device-scale for the role of adsorbents to be expanded. In this talk, we will discuss how additive manufacturing and the surface-segregation and vapor induced phase separation method for making membranes can be combined to fabricate sorbents with hierarchical structures. Solutions containing polysulfone and a polystyrene-block-poly(acrylic acid) (PS-PAA) block polymer were deposited as the filaments of microstructured sorbents utilizing solvent-assisted three-dimensional printing. Through the appropriate selection and control of the printing environment, the filaments were manufactured to possesses a bi-continuous network of pores ~500 nm in diameter. The poly(acrylic acid) (PAA) moieties of the block polymer, which segregate to the nanopore walls during fabrication, allowed the sorbent chemistry to be tailored for heavy metal removal via solid state coupling reactions. Here, terpyridine groups were incorporated along the pore wall to develop a sorbent capable of efficiently removing metal ions under conditions where the contamination is present at trace concentrations (e.g., < 10 ppm). The high metal binding affinity of the terpyridine moiety results in a sorbent that reaches its saturation capacity at bulk concentrations less than 1 mM. This molecular design enables the highly efficient purification of simulated ground water or seawater solutions by capturing 99⁺% of the metal ions dissolved in them. At the device-scale, the hierarchical structures of the sorbent reduce mass transfer limitations that hinder the performance of traditional resins. With their readily tunable surface chemistry and structures, these sorbents are a potential platform for the design and fabrication of devices that can be implemented in advanced separation and purification applications.