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1. Functionalized electrospun polymer nanofibers for treatment of water contaminated with uranium

   https://doi.org/10.1039/C9EW00834A  

   Johns, Adam; Qian, Jiajie; Carolan, Margaret E.; Shaikh, Nabil; Peroutka, Allison; Seeger, Anna; Cerrato, José M.; Forbes, Tori Z.; Cwiertny, David M. (March 2020, Environmental Science: Water Research & Technology)

   Uranium (U) contamination of drinking water often affects communities with limited resources, presenting unique technology challenges for U 6+ treatment. Here, we develop a suite of chemically functionalized polymer (polyacrylonitrile; PAN) nanofibers for low pressure reactive filtration applications for U 6+ removal. Binding agents with either nitrogen-containing or phosphorous-based ( e.g. , phosphonic acid) functionalities were blended (at 1–3 wt%) into PAN sol gels used for electrospinning, yielding functionalized nanofiber mats. For comparison, we also functionalized PAN nanofibers with amidoxime (AO) moieties, a group well-recognized for its specificity in U 6+ uptake. For optimal N-based (Aliquat® 336 or Aq) and P-containing [hexadecylphosphonic acid (HPDA) and bis(2-ethylhexyl)phosphate (HDEHP)] binding agents, we then explored their use for U 6+ removal across a range of pH values (pH 2–7), U 6+ concentrations (up to 10 μM), and in flow through systems simulating point of use (POU) water treatment. As expected from the use of quaternary ammonium groups in ion exchange, Aq-containing materials appear to sequester U 6+ by electrostatic interactions; while uptake by these materials is limited, it is greatest at circumneutral pH where positively charged N groups bind negatively charged U 6+ complexes. In contrast, HDPA and HDEHP perform best at acidic pH representative of mine drainage, where surface complexation of the uranyl cation likely drives uptake. Complexation by AO exhibited the best performance across all pH values, although U 6+ uptake via surface precipitation may also occur near circumneutral pH values and at high (10 μM) dissolved U 6+ concentrations. In simulated POU treatment studies using a dead-end filtration system, we observed U removal in AO-PAN systems that is insensitive to common co-solutes in groundwater ( e.g. , hardness and alkalinity). While more research is needed, our results suggest that only 80 g (about 0.2 lbs.) of AO-PAN filter material would be needed to treat an individual's water supply (contaminated at ten-times the U.S. EPA maximum contaminant level for U) for one year. 

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2. Liquid Crystals as Multifunctional Interfaces for Trapping and Characterizing Colloidal Microplastics

   https://doi.org/10.1002/smll.202207802  

   Mukherjee, Fiona; Shi, Anye; Wang, Xin; You, Fengqi; Abbott, Nicholas L. (March 2023, Small)

   Abstract Identifying and removing microplastics (MPs) from the environment is a global challenge. This study explores how the colloidal fraction of MPs assemble into distinct 2D patterns at aqueous interfaces of liquid crystal (LC) films with the goal of developing surface‐sensitive methods for identifying MPs. Polyethylene (PE) and polystyrene (PS) microparticles are measured to exhibit distinct aggregation patterns, with addition of anionic surfactant amplifying differences in PS/PE aggregation patterns: PS changes from a linear chain‐like morphology to a singly dispersed state with increasing surfactant concentration whereas PE forms dense clusters at all surfactant concentrations. Statistical analysis of assembly patterns using deep learning image recognition models yields accurate classification, with feature importance analysis confirming that dense, multibranched assemblies are unique features of PE relative to PS. Microscopic characterization of LC ordering at the microparticle surfaces leads to predict LC‐mediated interactions (due to elastic strain) with a dipolar symmetry, a prediction consistent with the interfacial organization of PS but not PE. Further analysis leads to conclude that PE microparticles, due to their polycrystalline nature, possess rough surfaces that lead to weak LC elastic interactions and enhanced capillary forces. Overall, the results highlight the potential utility of LC interfaces for rapid identification of colloidal MPs based on their surface properties. 

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3. Novel composite hydrogels containing fractionated, purified lignins for aqueous-based separations

   https://doi.org/10.1039/d0ta09046h  

   Gregorich, Nicholas; Ding, Junhuan; Thies, Mark C.; Davis, Eric M. (January 2021, Journal of Materials Chemistry A)

   null (Ed.)

   Herein, a series of novel, lignin-based hydrogel composites was fabricated by incorporating ultraclean lignins (UCLs), of controlled molecular weight and low dispersity, into poly(vinyl alcohol) (PVA). The UCLs were obtained from a novel liquid–liquid fractionation of high dispersity crude bulk lignins (CBLs) obtained from Kraft black liquor. A complementary series of composite hydrogels was fabricated using these CBLs. Both the CBLs and UCLs were functionalized with vinyl-containing acrylate groups allowing the lignins to chemically crosslink with themselves, forming an interpenetrated network with the thermally-crosslinked network of PVA chains. Successful functionalization of the UCLs was demonstrated by proton and phosphorous nuclear magnetic resonance. PVA–lignin hydrogels containing 20 wt% UCL saw a reduction in methylene blue (MB) permeability by approximately two orders of magnitude when compared to neat PVA. Further, for composite hydrogels containing either 50 wt% UCL or CBL, no MB was detected in the receiving reservoir over the duration of the permeation experiment. In general, an increase in Young's moduli was observed in PVA–lignin hydrogels containing CBLs, where hydrogels composed of 50 wt% CBLs exhibited ∼40% increase when compared to neat PVA. In contrast, a ∼10% reduction in Young's moduli was observed for composite hydrogels containing 20 wt% UCLs or less, though these membranes exhibited the lowest MB permeabilities of all membranes investigated. However, the largest increase in membrane stiffness was observed for composite hydrogels containing 50 wt% UCLs, where a ∼70% increase in Young's modulus was observed. Finally, the concentration and functionalization of the lignins was seen to have a direct impact on the network structure of the soft composites, where in general, the molecular weight between crosslinks is seen to decrease with increasing lignin concentration. 

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4. A bioinspired, passive microfluidic lobe filtration system

   https://doi.org/10.1039/D1LC00449B  

   Clark, Andrew S.; San-Miguel, Adriana (September 2021, Lab on a Chip)

   Size-based microfluidic filtration systems can be affected by clogging, which prevents their use in high-throughput and continuous applications. To address these concerns, we have developed two microfluidic lobe filters bioinspired by the filtration mechanism of two species of manta ray. These chips enable filtration of particles around 10–30 μm with precise control and high throughput by using two arrays of equally spaced filter lobes. For each filter design, we investigated multiple inlet flow rates and particle sizes to identify successful operational parameters. Filtration efficiency increases with fluid flow rate, suggesting that particle inertial effects play a key role in lobe filter separation. Microparticle filtration efficiencies up to 99% were obtainable with inlet flow rates of 20 mL min −1 . Each filter design successfully increased microparticle concentrations by a factor of two or greater at different inlet flow rates ranging from 6–16 mL min −1 . At higher inlet flow rates, ANSYS Fluent simulations of each device revealed a complex velocity profile that contains three local maxima and two inflection points. Ultimately, we show that distances from the lobe array to the closest local maxima and inflection point of the velocity profile can be used to successfully estimate lobe filtration efficiency at each operational flow rate. 

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5. Evaluation, optimization study, and life cycle assessment of novel eco-friendly PVA-based nanocomposite hydrogel adsorbents for methylene blue and paracetamol removal

   https://doi.org/10.1016/j.ecoenv.2024.117123  

   Elessawy, Noha A; Alhamzani, Abdulrahman G; Almahmoud, Sondos AJ; Hsiao, Benjamin S (September 2024, Ecotoxicology and environmental safety)

   In this study, an eco-friendly and novel hydrogel based on a crosslinked polyvinyl alcohol (PVA), iota carrageenan (IC) and polyvinylpyrrolidone (PVP) scaffold, containing a large amount (10–50 wt%) of nanoscale palm fronds (NPF) as additives, for water purification was demonstrated. A life cycle assessment (LCA) findings on NPF as biomass waste incorporated into PVA_PVP_IC polymer matrix was presented, and the results highlight the necessity of focused actions to reduce environmental impact and support the palm waste utilization in a sustainable manner. The multicomponent nanocomposite hydrogels were examined as adsorbents in a system work in batches for methylene blue (MB) and paracetamol (PCT) removal. The results show that, the presence of NPF, which dispersed in the hydrogel PVA_PVP_IC scaffolds containing both covalent and non-covalent cross-linking bonds, greatly enhanced the MB and PCT adsorption efficiency. A response surface methodology (RSM) model was used to find the best operating parameters of contaminant adsorption, including time, adsorbent dose, and starting concentration of pollutants. By using this statistical model, it was found that the optimal conditions for the adsorption reaction to achieve the complete removal of MB are 66.7 h adsorption time duration, 98.5 mg/L starting concentration, and an adsorbent dose of 5.9 mg, while for the complete removal of PCT, it is 57.6 h adsorption time duration, 80 mg/L starting concentration, and an adsorbent dose of 6 mg. The reusability of the nanocomposite hydrogels were tested for 5 cycles, all showed high adsorption capacity, indicating the potential for practical application of this nanocomposite hydrogel system. This study indicates that the prepared nanocomposite hydrogel raises the standard used for treatment of wastewater and also gives a solution to protect the environment and mitigate global warming. 

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