Implications and Applications of Nanomaterials for Membrane-Based Water Treatment

The environmental engineering community's assessment of nanomaterials is deeply nuanced. On one hand, nanomaterials are recognized as emerging contaminants with potential implications for human and environmental well-being. On the other hand, properties found unique to the nanoscale enable novel environmental technologies benefiting human and natural systems. This dual reality demands that environmental technologies are simultaneously conscious of nanomaterial implications and embracing of nanomaterials' promise. The work performed in this thesis demonstrates the potential of membranes as a platform for realizing nanomaterial applications while minimizing environmental release and associated risks.;The present work addresses the environmental applications and implications of nanomaterials in 6 parts. Part I reviews the novel properties of carbonaceous materials at the nanoscale, highlighting the structural and material characteristics that contribute to nanomaterial toxicity and environmental applications. Part II expands our understanding of nanomaterial toxicity in an experimental investigation linking the physicochemical properties of carbonaceous nanomaterials to their toxicity in laboratory and environmental systems. Part III critically reviews the environmental applications of carbonaceous nanomaterials and provides insight into me future growth trajectories and limitations of these technologies. Part IV expands on one environmental application, aligned carbon nanotube membranes, and proposes a technique for the post-synthesis fabrication of aligned single-walled carbon nanotube thin-film composites with future applications in water desalination. Membranes and other thin-films are a particularly promising platform for the realization of nanomaterial properties, due to their ease of fabrication and integration into existing technology platforms. Part V presents the scientific challenges of fabricating such functional nanocomposite membranes and describes a novel technique for grafting the surface of ultrafiltration membranes with silver nanoparticles. Part VI concludes by presenting two tools for assessing the environmental costs and benefits of nanomaterial incorporation into environmental technologies.;This work advances the concept that nanomaterials---and, by extension, other emerging technologies---present a tradeoff between applications and implications. Experimental investigations, as well as systemic analysis tools, are critical to identifying low-impact nanomaterial applications in environmental systems. Membranes are a uniquely promising platform for realizing nanomaterial application in a low impact, effective, and cost-efficient manner.