Efficient dye adsorption by highly porous nanofiber aerogels

Electrospun nanofiber membranes are frequently used in adsorption processes thanks to their high specific surface area, tailored surface functionality, and fiber uniformity. However, they are still facing challenges such as low mechanical stability and unfavorable mass transport properties. In this study, an ultra-light and robust 3D nanofiber aerogel (NFA) or nanofiber sponge with tunable porosity and flexibility was synthesized from short pullulan/polyvinyl alcohol/polyacrylic acid nanofibers using a freeze casting process followed by thermal crosslinking. We demonstrate time the application of such NFAs in batch and continuous adsorption systems and compare their performance with flat nanofiber membranes (NFM). The NFAs proved to be promising adsorbents for cationic dyes due to their high adsorption capacity (383 mg/g) and their reusability. Langmuir isotherm was a suitable model for describing the adsorption process. The endothermic system followed a pseudo second order kinetic model and intra-fiber adsorption is found to be involved in the adsorption process. Dye adsorption by 3D NFAs was four times faster than for the respective flat NFMs and when used in a continuous process as a deep-bed filter, the pressure drop through the NFA was reduced by a factor of 40 while maintaining equal adsorption performance as for the NFM

Welches Gas steckt im Öl? : Integrierte Diagnostik gibt Antwort

Leistungstransformatoren sind das Rückgrat unserer Stromversorgung. Um deren sicheren Betrieb zu gewährleisten, müssen sie turnusmässig überwacht werden. Zur Diagnose ist unter anderem die Analyse von gelösten Gasen wie Wasserstoff, Methan, oder Acetylen vorgeschrieben (Dissolved Gas Analysis DGA nach IEC 60599). Diese ist sehr aufwändig, da weltweit Ölproben entnommen und zur Analyse verschickt werden müssen. Ein integriertes Messverfahren ist deshalb eine interessante Alternative

Linking Gulf Stream air–sea interactions to the exceptional blocking episode in February 2019: a Lagrangian perspective

The development of atmospheric blocks over the North Atlantic–European region can lead to extreme weather events like heat waves or cold air outbreaks. Despite their potential severe impact on surface weather, the correct prediction of blocking lifecycles remains a key challenge in cur- rent numerical weather prediction (NWP) models. Increasing evidence suggests that latent heat release in cyclones, the advection of cold air (cold air outbreaks, CAOs) from the Arctic over the North Atlantic, and associated air–sea interactions over the Gulf Stream are key processes contribut- ing to the onset, maintenance, and persistence of such flow regimes. To better understand the mechanism connecting air-sea interactions over the Gulf Stream with changes in the large-scale flow, we focus on an episode between 20 and 27 February 2019, when a quasi-stationary upper-level ridge was established over western Europe accompanied by an intensified storm track in the northwestern North Atlantic. During that time, a record-breaking winter warm spell occurred over western Europe bringing temperatures above 20$^◦$C to the United Kingdom, the Netherlands, and northern France. The event was preceded and accompanied by the develop- ment of several rapidly intensifying cyclones that originated in the Gulf Stream region and traversed the North Atlantic. To explore the mechanistic linkage between the formation of this block and air–sea interactions over the Gulf Stream, we adopt a Lagrangian perspective, using kinematic trajec- tories. This allows us to study the pathways and transformations of air masses that form the upper-level potential vorticity anomaly and interact with the ocean front. We establish that more than one-fifth of these air masses interact with the Gulf Stream in the lower troposphere, experiencing intense heating and moistening over the region due to the frequent occurrence of CAOs behind the cold front of the cyclones. Trajectories moistened by the advection of cold air over a warm ocean by one cyclone later ascend into the upper troposphere with the ascending airstream of a subsequent cyclone, fueled by the strong surface fluxes. These findings highlight the importance of CAOs in the Gulf Stream region, indicat- ing that their intense coupling between the ocean and atmosphere plays a role in block development. Additionally, they provide a mechanistic pathway linking air–sea interactions in the lower troposphere and the upper-level flow

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Amphiphilic nanofiber based aerogels from electrospun biopolymers for selective liquid absorption

Hierarchically structured and ultralight pullulan/PVA aerogels or sponges were prepared from short electrospun nanofibers using solid templating. The architecture of the aerogel consisted of cell-like pores of 50 to 100 µm interconnected by a network of entangled nanofibers with 2 to 5 µm pores. Such structures allow rapid liquid uptake with high liquid holding capacities at the same time. The amphiphilic nature of the aerogel from the electrospun biopolymer was switched by chemical vapor deposition of silane. This allows the selective separation of liquids based on their different relative dielectric constants, which is of high interest for oil spilled waters and produced water. Furthermore, silylation improved the aerogel’s overall mechanical stability by 18 % while increasing its density by only 5 %. SEM in situ compression studies revealed the importance of the fibrous entanglement and the open-porous architecture for the high bendability and mechanical resilience of the aerogels. Solid templating of short electrospun nanofibers facilitates the design of a fascinating class of ultralight aerogels while prevailing the fibrous character and the versatility of electrospinning

Exploration of ultralight nanofiber aerogels as particle filters : capacity and efficiency

Ultralight nanofiber aerogels (NFAs) or nanofiber sponges are a truly three-dimensional derivative of the intrinsically flat electrospun nanofiber mats or membranes (NFMs). Here we investigated the potential of such materials for particle or aerosol filtration because particle filtration is a major application of NFMs. Ultralight NFAs were synthesized from electrospun nanofibers using a solid-templating technique. These materials had a tunable hierarchical cellular open-pore structure. We observed high filtration efficiencies of up to 99.999% at the most penetrating particle size. By tailoring the porosity of the NFAs through the processing parameters, we were able to adjust the number of permeated particles by a factor of 1000 and the pressure drop by a factor of 9. These NFAs acted as a deep-bed filter, and they were capable of handling high dust loadings without any indication of performance loss or an increase in the pressure drop. When the face velocity was increased from 0.75 to 6 cm s-1, the filtration efficiency remained high within a factor of 1.1-10. Both characteristics were in contrast to the behavior of two commercial NFM particle filters, which showed significant increases in the pressure drop with the filtration time as well as a susceptibility against high face velocities by a factor of 105