This study addresses the pervasive challenge of biofouling in seawater desalination systems, which compromises membrane performance and longevity, by introducing a multifunctional PDA-SP-cTA coating. This bio-inspired coating effectively mitigates biofouling in seawater reverse osmosis systems without requiring biocide. The coating is applied to both hydrophilic polyamide membranes and hydrophobic polypropylene feed spacers through in-situ and ex-situ polymer deposition methods, involving a single-step process with polydopamine and sodium-periodate, followed by surface tailoring with citric acid-blended tannic acid. Extensive surface characterization, primarily conducted on polypropylene feed spacers, confirms coating deposition. Antibiofouling properties are evaluated through long-term biofouling tests simulating industrial conditions. The findings demonstrate that the ex-situ applied coating significantly reduces relative feed channel pressure drop increase due to biofilm growth by 75 % and lowers biomass accumulation (88 % total cell counts, 70 % adenosine-triphosphate, 91 % carbohydrates, and 69 % proteins). The coating inhibits the colonization of biofouling-causing bacterial genus Alteromonas, drastically decreases active bacterial gene copy numbers, and alters microbial composition, leading to reduced biofilm viability and loosely attached biofilms that could enhance cleaning efficiency. This comprehensive study encompasses the entire process from the strategic selection and systematic characterization of the coating to extensive biofouling tests and stability assessments offering a holistic solution to combat biofouling without biocides. With demonstrated durability and stability across various pH conditions over time, this coating could be a widely applicable and scalable solution for biofouling mitigation in diverse industrial contexts.

Dense polymer membranes enable a diverse range of separations and clean energy technologies, including gas separation, water treatment, and renewable fuel production or conversion. The transport of small molecular and ionic solutes in the majority of these membranes is described by the same solution-diffusion mechanism, yet a comparison of membrane separation performance across applications is rare. A better understanding of how structure-property relationships and driving forces compare among applications would drive innovation in membrane development by identifying opportunities for cross-disciplinary knowledge transfer. Here, we aim to inspire such cross-pollination by evaluating the selectivity and electrochemical driving forces for 29 separations across nine different applications using a common framework grounded in the physicochemical characteristics of the permeating and rejected solutes. Our analysis shows that highly selective membranes usually exhibit high solute rejection, rather than fast solute permeation, and often exploit contrasts in the size and charge of solutes rather than a nonelectrostatic chemical property, polarizability. We also highlight the power of selective driving forces (e.g., the fact that applied electric potential acts on charged solutes but not on neutral ones) to enable effective separation processes, even when the membrane itself has poor selectivity. We conclude by proposing several research opportunities that are likely to impact multiple areas of membrane science. The high-level perspective of membrane separation across fields presented herein aims to promote cross-pollination and innovation by enabling comparisons of solute transport and driving forces among membrane separation applications.

Electrochemical reduction of carbon dioxide (CO₂R) poses substantial promise to convert abundant feedstocks (water and CO₂) to value-added chemicals and fuels using solely renewable energy. However, recent membrane-electrode assembly (MEA) devices that have been demonstrated to achieve high rates of CO₂R are limited by water management within the cell, due to both consumption of water by the CO₂R reaction and electro-osmotic fluxes that transport water from the cathode to the anode. Additionally, crossover of potassium (K⁺) ions poses concern at high current densities where saturation and precipitation of the salt ions can degrade cell performance. Herein, a device architecture incorporating an anion-exchange membrane (AEM) with internal water channels to mitigate MEA dehydration is proposed and demonstrated. A macroscale, two-dimensional continuum model is used to assess water fluxes and local water content within the modified MEA, as well as to determine the optimal channel geometry and composition. The modified AEMs are then fabricated and tested experimentally, demonstrating that the internal channels can both reduce K⁺ cation crossover as well as improve AEM conductivity and therefore overall cell performance. This work demonstrates the promise of these materials, and operando water-management strategies in general, in handling some of the major hurdles in the development of MEA devices for CO₂R.