Biomimetic Active Chemical Separation

Abstract

This dissertation embarks on an exploration of nature's design principles in the realm of chemical separation and transfer, with the overarching goal of applying these insights to address pressing real-world challenges. Our journey begins with a comprehensive review of prevailing industrial chemical separation techniques, revealing their remarkable energy demands and the unfortunate squandering of unrecoverable energy. This realization serves as a catalyst for our quest to draw inspiration from the intricate, yet efficient solutions nature offers, particularly exemplified by the cell membrane's remarkable ability to discern among myriad compounds using a seemingly straightforward design.The cell membrane in living organisms serves as an emblem of nature's ingenuity. Equipped with delicate membrane proteins, each devoted to specific functions vital for the cell's existence, it operates with a sophistication that continues to elude our full understanding. Yet, our quest is not to replicate nature but to draw inspiration from it. We take the humble dialysis machine as an exemplary case, a technology characterized by its relatively simple design. This apparatus, functioning as an artificial kidney, relies on precision-controlled transmembrane separation facilitated by hollow fiber membranes with precise pore sizes, complemented by mechanical pumps and dialysate. Despite its apparent simplicity, this technology remains a lifeline for patients awaiting kidney transplants. Nevertheless, we acknowledge the imperative to enhance its long-term survival rates. From a materials science perspective, our pursuit of advancement in these technologies hinges on the development of superior functional materials. For dialysis, this translates into better control of pore size distribution and porosity, a journey we embark upon through the development of hollow fiber membranes. However, the intrinsic limitation of passive diffusion in dialysis technology necessitates a shift towards biomimetic active high-selectivity functionalization. In response, we design, propose, synthesize, and validate selective surface chemistry modifications for serum albumin. This groundbreaking surface chemistry enhancement facilitates the adsorption and desorption cycling of albumin, concurrently removing protein-bound uremic toxins that defy conventional dialysis processes. Moreover, our journey extends to the scaling-up of this technology, underpinned by systematic design implementation and continuous refinements guided by computational models. Likewise, in our pursuit of dialysis technology enhancement, we explore the modification of highly selective functional groups onto low-cost silica adsorbents. This endeavor aims to efficiently remove potassium ions enriched in dialysates during the development of mobile dialysis techniques. Despite the availability of various adsorbents and natural materials, we opt for silica adsorbents due to their stability, cost-effectiveness, and ease of preparation. The modified crown ether-silica adsorbents exhibit remarkable potassium ion adsorption capacity, promising applications beyond conventional adsorbents. Our expedition also ventures into the domain of carbon material-based membranes, particularly carbon nanotubes and reduced graphene oxide membranes. These materials hold the potential to revolutionize separation processes by compensating for membrane structure surface area limitations. Under nanoscale confinement, they achieve high-speed transmembrane fluid transport, outperforming conventional adsorbent-based methods. We make history by directly observing high-speed transmembrane electroosmotic transport within carbon nanotubes, marking a significant milestone in our journey. The observations from this study underscore the promise of carbon nanotube membranes, especially when functionalized with high-selectivity functional groups. We validate the concept of transmembrane drug delivery on negatively modified carbon nanotube membranes, showcasing their potential in various applications. In our exploration of graphene oxide membranes, we unearth a fascinating catalytic reaction, offering unique selectivity. However, this discovery comes with the challenge of reduced interlayer spacing, limiting transmembrane separation rates. We surmount this challenge by ingeniously reintroducing substances that reverse the catalytic reaction, enabling high-speed fluid passage and salvaging the potential of graphene oxide membranes in alcohol dehydration applications. In conclusion, this dissertation's comprehensive exploration of materials science and biomimetic high-selectivity surface chemistry modification yields profound insights. Our research validates scientific theories and overcomes engineering constraints, heralding a promising future for separation technologies. As we continue to draw inspiration from nature's design, the possibilities for addressing real-world challenges through biomimicry are vast and exciting.