17 research outputs found

    Tailoring the Surface Chemistry of Anion Exchange Membranes with Zwitterions: Toward Antifouling RED Membranes

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    Fouling is a pressing issue for harvesting salinity gradient energy with reverse electrodialysis (RED). In this work, antifouling membranes were fabricated by surface modification of a commercial anion exchange membrane with zwitterionic layers. Either zwitterionic monomers or zwitterionic brushes were applied on the surface. Zwitterionic monomers were grafted to the surface by deposition of a polydopamine layer followed by an aza-Michael reaction with sulfobetaine. Zwitterionic brushes were grafted on the surface by deposition of polydopamine modified with a surface initiator for subsequent atom transfer radical polymerization to obtain polysulfobetaine. As expected, the zwitterionic layers did increase the membrane hydrophilicity. The antifouling behavior of the membranes in RED was evaluated using artificial river and seawater and sodium dodecylbenzenesulfonate as the model foulant. The zwitterionic monomers are effective in delaying the fouling onset, but the further build-up of the fouling layer is hardly affected, resulting in similar power density losses as for the unmodified membranes. Membranes modified with zwitterionic brushes show a high potential for application in RED as they not only delay the onset of fouling but they also slow down the growth of the fouling layer, thus retaining higher power density outputs

    Cultural heritage adaptive reuse in Salerno: Challenges and solutions

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    The adaptive reuse of cultural heritage contributes to heritage conservation, leveraging on the heritage potential to enable sustainable development and enhance urban livability. Yet, it is seldom applied as intervention. This research furthers the knowledge on the challenges to the adaptive reuse of cultural heritage. Through the case study of Salerno (Italy) and a participatory methodology, this research organized a stakeholder engagement workshop, facilitating the interaction of stakeholders—representing the public, private, civic, and knowledge sectors, while using a theoretical framework based on the six steps of the UNESCO Historic Urban Landscape approach to adopt a multi-scale perspective. The content analysis of the data reveals 55 themes encompassing challenges and solutions. These themes are presented in a general overview, followed by an in-depth reporting of the five most discussed themes, i.e. knowledge production and management, participation, valorization, approaches, and cooperation. Besides the contribution to science, this research also offers an overview of challenges and possible solutions for prospective stakeholders in the adaptive reuse of cultural heritage, informing future decision- and policy-making activities towards greater sustainable development within the built environment.</p

    Predicting reverse electrodialysis performance in the presence of divalent ions for renewable energy generation

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    Reverse electrodialysis (RED) is an electro-membrane process to harvest renewable energy from salinity gradients. RED process models have been developed in the past, but they mostly assume that only NaCl is present in the feedwaters, which results in unrealistically high predictions. In the present work, an existing simple model is extended to accommodate the presence of magnesium ions and sulfate in the feedwaters, and potentially even more complex mixtures. All power loss mechanisms deriving from the presence of multivalent ions are included in the new model: increased membrane electrical resistance, uphill transport of multivalent ions from the river to the seawater compartment, and membrane permselectivity loss. This new model is validated with experimental and literature data of membrane electrical resistance (at 10 mol. % MgCl2 for the CEMs and 25 mol. % Na2SO4 for the AEMs), RED stack performance (up to 50 mol. % MgCl2 or Na2SO4 in the feedwaters), and ion transport (at 10 mol. % MgCl2 or Na2SO4 in the feedwaters) showing very good agreement between model predictions and experimental data. Finally, we showed that the developed model not only describes experimental data but can also predict RED performances under a variety of conditions and cross-flow configurations (single-stage with and without electrode segmentation, multi-stage in co-current and counter-current mode) and feedwater compositions (only NaCl, with Na2SO4, with MgCl2, and with MgSO4). It thus provides a very valuable tool to design and evaluate RED process systems

    Combining stereolithography and replica molding : on the way to superhydrophobic polymeric devices for photovoltaics

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    A strategy combining stereolithography (SL) and soft-lithography for the straightforward fabrication of superhydrophobic bulk devices is reported. Microtextured masters are rapidly prototyped by SL and passivated with a perfluorosilane. Such surface treatment enables the faultless fabrication of negative microstructured polydimethylsiloxane molds ultimately utilized to obtain bulk polymeric micropatterned structures by replica molding. As illustrative proof of concept, this approach is employed in the field of photovoltaics to realize the first example of superhydrophobic luminescent solar concentrators (LSCs) showing superior self-cleaning properties. Following our strategy, a new dye-doped acrylate mixture is developed and optimized to ensure complete wetting of the hollow microstructures present on the mold. By judiciously tailoring the photoinitiator concentration and by implementing a tailored double-step UV-irradiation process, complete UV-photopolymerization is achieved despite the significant thickness of the target samples. The high fidelity replication of the original SL-printed features on the daughter replicas as well as their super water-repellency are successfully demonstrated. The performance of the resulting superhydrophobic LSCs is investigated at varying device dimensions and found to be comparable with state-of-the-art systems. This study demonstrates the potential of high-resolution SL-printing in combination with replication techniques as a versatile tool to reproducibly fabricate microstructured superhydrophobic polymeric bulk devices in a straightforward fashion

    Influence of sulfate on anion exchange membranes in reverse electrodialysis

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    Reverse electrodialysis (RED) is a technology producing renewable energy from the mixing of river and seawater. In natural salinity gradients, multivalent ions are present, which lead to a reduced RED power output. Transport of multivalent ions against the concentration gradient and their trapping inside the membranes leads to a lower driving force and increased membrane resistance. The present work focuses on the effect of sulfate ions on anion exchange membranes in RED. A monovalent ion selective membrane ability to retain a higher open circuit voltage is offset by the higher resistance in the presence of sulfate, leading to losses in normalized power outputs (−25%) comparable to a standard grade membrane. Longer term experiments revealed that membrane resistance increases over time. This study highlights the need to address uphill transport, resistance increase, and decreased permselectivity of anion exchange membranes in presence of multivalent ions

    Electrode segmentation in reverse electrodialysis: Improved power and energy efficiency

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    Reverse electrodialysis harvests energy from salinity gradients establishing a renewable energy source. High energy efficiencies are fundamental to up-scale the process and to minimize feedwater pre-treatment and pumping costs. The present work investigates electrode segmentation to strategically optimize the output power density and energy efficiency. Electrode segmentation allows the current density to be tuned per electrode segment. Segmentation experiments were performed with a dedicated electrode configuration in a cross-flow stack using a wide range of residence times. Moreover, an experimentally validated model was extended and used to further compare single and segmented electrode configurations. While operating the electrode segments, the highest efficiencies were obtained when considering the overall power, i.e. not maximized by segment. Results show that at a given net power density (0.92 W·m−2), electrode segmentation increases the net energy efficiency from 17% to 25%, which is a relative increase of 43%. Plus, at 40% net energy efficiency the net power output for a segmented electrode configuration (0.67 W·m−2) is 39% higher than in a single electrode configuration. Higher power density reduces capital investment and higher energy efficiency reduces operating costs. Electrode segmentation increases these parameters compared to a single electrode and can be potentially applied for up-scaling
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