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We investigate the capillary driven collapse of a small contracting cavity or hole in a shear-thinning fluid. We find that shear-thinning effects accelerate the collapse of the cavity by decreasing the apparent liquid viscosity near the cavity's moving front. Scaling arguments are used to derive a power-law relationship between the size of the cavity and the rate of collapse. The scaling predictions are then corroborated and fully characterized using high-fidelity simulations. The new findings have implications for natural and technological systems including neck collapse during microbubble pinch-off, the integrity of perforated films and biological membranes, the stability of bubbles and foams in the food industry, and the fabrication of nanopore based biosensors. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ca-HAP: a suitable surface for trapping Cr3+ also in co-presence of other metal ions. • Cr uptake mechanism involves both ion exchange with Ca ions and surface complexation. • Cr3+ is strongly retained on HAP surface at both acidic and basic pH of solutions. • Functional groups on HAP surface play a key role in the complexation of metal ions. Abstract In the present study, the efficiency and selectivity and the role of surface groups of hydroxyapatite in the Cr(III) trapping, present in solution as single species or in co-presence of Ni(II) and Pb(II), have been investigated. Transmission electron microscopy (TEM) analysis and synchrotron radiation X-ray powder diffraction (XRPD) measurements provided comprehensive descriptions of the HAP surface and structure. The surface chemical properties, density and strength of the acid and base sites of HAP, have been determined by 2-phenylethylamine and benzoic acid probe adsorption, respectively. The amphoteric properties of HAP turned over to only acid property in water solution. The sorption capacity of HAP has been batch-tested in simulated polluted waters containing Cr(III) at different initial concentrations (from ca. 0.3 to ca.6 mM) and pH values (from 4 to 9). Competitive adsorption phenomena in multi-metal systems (Cr(III) with Ni(II) and Pb(II)) have also been studied. An appropriate set of analytical techniques, XRPD, TEM, STEM-EDX, N 2 adsorption-desorption analyses, FT-IR spectroscopy, have been used to characterize the metal loaded hydroxyapatite samples. Different mechanisms of metal uptake were active depending on the nature of the metal species and pH value of solutions: surface complexation, precipitation, ion-exchange, or dissolution-precipitation. [ABSTRACT FROM AUTHOR]

In the present study, the Ni(II) and Co(II) adsorption efficiency and selectivity, as well adsorption mechanisms on a stoichiometric hydroxyapatite (HAP) surface have been investigated. Characterization studies (N2 adsorption/desorption and X-ray powder diffraction (XRPD) analyses) and adsorption tests under various operative conditions provided detailed information about the use of HAP in the de-metalation of wastewaters containing Ni and Co as polluted metal species. The sorption capacity of HAP has been evaluated by static batch adsorption tests varying initial concentration of Ni(II) and Co(II) species (from ca. 0.25 to 4.3 mM), contact time (from 15 min to 24 h), and pH (from 4 to 9) operative parameters. Proposed mechanisms of adsorption of Ni(II) and Co(II) on HAP surface are ion-exchange and surface complexation; a partial contribution of chemical precipitation from bulk solution should be considered at pH 9. In addition, adsorption isotherms of Ni(II) and Co(II) on HAP have been collected at 30 °C and pH 4 and modeled by employing different equations. The maximum sorption capacities have been quantified as 0.317 mmol g HAP - 1 (18.6 mg g HAP - 1 ) and 0.382 mmol g HAP - 1 (22.5 mg g HAP - 1 ) for Ni(II) and Co(II), respectively. Selectivity to Co and Ni in the adsorption process on HAP has also been investigated; HAP has higher affinity towards Co than Ni species (Co:Ni = 2.5:1, molar ratio). [ABSTRACT FROM AUTHOR]

In this paper, we report on the rational design, synthesis, characterization, and application of eco-friendly hydroxyapatite/carbon (HAP/C) composites as effective sorbents for the simultaneous remediation of organic-inorganic pollution in wastewaters. Carbon content in composites ranged from ca. 4 to ca. 20 wt%. Structural and morphological features of the composites were studied by N 2 adsorption/desorption analyses, electron microscopy (TEM and HAADF-STEM/EDX) and X-ray powder diffraction (XRPD). These features were correlated with the composition and the exposure of surface functional groups. Surface acid-base groups were assessed by liquid-solid acid/base titrations and results depended on the composition ratio of the two components. Batch adsorption tests, performed with various initial concentrations of pollutant species and dosages, proved that composites merged the sorption properties of the two moieties, being able to simultaneously adsorb organic (methylene blue) and inorganic (Cu(II) and Ni(II)) pollutants. On the optimal carbonaceous scaffold content (ca. 8 wt% carbon), kinetic tests revealed that this composite could almost completely remove high concentrations of co-present pollutants, namely, Cu(II), Ni(II), (300 ppm) and methylene blue (250 ppm) in ca. 1 h, with sorbent dosage of 10 g L−1. In addition, leaching tests proved the permanent retention of the hazardous species on the composites. Graphical depiction of the interfacial phenomena of adsorption which take place at the solution-HAP/CMC composites interface, resulting in the simultaneous removal of organic and inorganic pollutants from wastewaters. [Display omitted] • Efficient HAP/CMC sorbents may be synthesized from ecofriendly, cheap precursors. • Dual nature composites allow organic/inorganic water pollutants one-step removal. • Structurally flexible and functionalized HAP surface allows inorganic sorption. • Large surface area and hydrophobicity of activated carbon rule organic sorption. • Permanent retention of pollutants onto the composites avoids secondary pollution. [ABSTRACT FROM AUTHOR]

The development of hydrogen storage and conversion technologies, such as electrolyzers and fuel cells, significantly benefits from the electrochemical deposition of platinum (Pt). This process is also crucial for creating coatings for internal combustion engines and electronic devices. Conventionally, Pt electrochemical deposition occurs in acidic media, which efficiently dissolves Pt salts but necessitates the use of expensive, corrosion-resistant substrates like noble metals and other critical raw materials such as titanium (Ti). This research explores the alkaline electrochemical deposition of Pt, aiming to overcome the limitations associated with acidic media. The study begins with developing strategies to dissolve commonly used Pt precursors from acidic baths into stable complexes suitable for alkaline environments. Various protocols, including chronoamperometric and potentiometric ones, are employed to evaluate the Pt electrodeposition on substrates such as nickel (Ni) foams and stainless steel meshes, which are relevant to alkaline water electrolysis. Optimization of the electrochemical deposition parameters is carried out to enhance the hydrogen evolution reaction (HER) activity of the resulting electrodes. The most HER-active electrodes are then tested as cathodes in alkaline electrolyzers (AELs), demonstrating superior performance compared to commercially available platinized Ti felts. These advanced AELs can operate at high current densities (≥1 A cm⁻2) at cell voltages below 2 V, thereby rivaling state-of-the-art acidic water electrolysis systems. Looking forward, the alkaline electrodeposition of Pt presents a sustainable approach to the usage of Pt in green hydrogen production. Pt recovered from operating or end-of-life electrolyzers and fuel cells can be reused to restore or enhance the catalytic activity of cathodes in alkaline water electrolysis, ensuring efficient and eco-friendly Pt utilization. [Display omitted] • Alkaline electrochemical deposition of Pt explored on various substrates used in AELs and AEM-ELs. • Pt precursors can form stable complexes in 1 M and 6.9 M KOH at 70 °C. • Fine-tuned Pt films achieve overpotential as low as 0.067 V at −100 mA cm⁻2. • Electrochemically deposited Pt films were validated in high-performance AEL cells. • In-situ electrochemical Pt deposition can be used for upgrading/healing AEL and AEM-EL cathodes. [ABSTRACT FROM AUTHOR]

This paper studies the cooperative effect of Au nanoparticles deposited on vanadyl pyrophosphate oxide (VPO) in the liquid phase oxidation of benzyl alcohol. VPO was prepared using the classical method by thermally treating VOHPO4·0.5H2O precursor in reacting atmosphere at 420 °C for a period of 72 h. Au nanoparticles were deposited by incipient wetness method. The catalysts were characterized by means of XRD, TEM, XPS and Raman. The bulk VPO catalyst contains vanadyl pyrophosphate phase ((VO)2P2O7), and a small amount of VOPO4. The catalytic system exhibits a high activity in the base-free liquid phase oxidation of alcohols compared to Au on activated carbon, classic catalyst used for this type of reaction. Au/VPO showed a high peculiar selectivity to benzyl benzoate (76%), an important product used in the pharmaceutical and perfume industries. This behavior might be ascribed to the presence of strong acid sites of VPO, as determined by liquid phase titration. Stability tests performed on Au/VPO showed a deactivation of 10% after the first run, but a constant conversion along the following five cycles. This phenomenon can be attributed to the increase of mean Au particle size (from 19.1 to 23.4 nm) after recycling tests as well as the partial leaching of Au and V in the reaction media. Moreover, XRD evidenced a modification in the VPO structure with the partial formation of VOHPO4·0.5H2O phase. [ABSTRACT FROM AUTHOR]

The increasing rate of adoption of innovative technological achievements along with the penetration of the Next Generation Internet (NGI) technologies and Artificial Intelligence (AI) in the water sector are leading to a shift to a Water-Smart Society. New challenges have emerged in terms of data interoperability, sharing, and trustworthiness due to the rapidly increasing volume of heterogeneous data generated by multiple technologies. Hence, there is a need for efficient harmonization and smart modeling of the data to foster advanced AI analytical processes, which will lead to efficient water data management. The main objective of this work is to propose two Smart Data Models focusing on the modeling of the satellite imagery data and the flood risk assessment processes. The utilization of those models reinforces the fusion and homogenization of diverse information and data, facilitating the adoption of AI technologies for flood mapping and monitoring. Furthermore, a holistic framework is developed and evaluated via qualitative and quantitative performance indicators revealing the efficacy of the proposed models concerning the usage of the models in real cases. The framework is based on the well-known and compatible technologies on NGSI-LD standards which are customized and applicable easily to support the water data management processes effectively. [ABSTRACT FROM AUTHOR]

There is much about the action of bismuth within heterogeneous catalysis that still require a deeper understanding. We observed that, when Bi was added to AuPd bimetallic nanoparticles (NPs) supported on activated carbon, Bi affected the activity and significantly alters the selectivity in two model liquid phase reactions, namely the oxidation of cinnamyl alcohol and the hydrogenation of cinnamaldehyde. A combination of transmission electron microscopy and X-ray absorption spectroscopy provided a detailed characterization of trimetallic AuPdBi systems. We propose that the introduction of bismuth on AuPd NPs results in a partial blockage of most active sites, limiting the occurrence of consecutive reactions. [Display omitted] • Bi addition to AuPd/AC depresses activity in oxidation and hydrogenation reactions. • Low amount of Bi (1 wt%) produces a significative enhancement in the selectivity. • Segregated bismuth oxide is in close contact with trimetallic AuPdBi nanoparticles. • Bi physically hinders the most active sites, limiting side reaction occurrence. [ABSTRACT FROM AUTHOR]

The development of efficient and cost-effective water splitting electrolyzers is a fundamental step to support the achievement of climate neutrality by using renewable energy sources to produce green H 2 as a form of clean fuel. In this work, we investigated Pt-based nanostructured cathodes for high-performance alkaline electrolyzers (AELs), showing the beneficial effect of graphene over traditional carbon black as nanocatalysts support. By relying on a water-based, scalable, synthetic method, surface-cleaned Pt nanoparticles were successfully produced and strongly anchored to defect-free graphene flakes, the latter produced through wet-jet milling exfoliation of natural graphite. Once deposited on conventional gas diffusion layers, Pt/graphene catalysts outperform traditional Pt on Vulcan (Pt/C) in terms of hydrogen evolution reaction (HER) activity and performance durability. The two-dimensional morphology of graphene flakes strongly retains the catalysts in the electrode even in the absence of any binder, while intrinsically ensuring the exposure of the catalytic sites for the HER. This rationale enables the fabrication of high-performance AELs based on Pt/graphene cathodes. By using commercially available cost-effective anodes (stainless-steel meshes), our AELs reached current densities of 1 A cm−2 at a voltage of as low as 1.71 V. These AELs can even operate up to more than 2 A cm−2 (e.g., 2.2 A cm−2 at 1.90 V), with stable performance during accelerated stress tests. Our study discloses two main aspects: (1) graphene is an effective conductive support for 1–10 nm-scale catalysts for the development of nanostructured cathodes with elevated catalytic properties and durable performance; (2) the use of efficient nanostructured cathodes can boost the AEL's performance to state-of-the-art values reported for proton-exchange membrane electrolyzers, avoiding the use of expensive anodes (e.g., Ir-based ones). [ABSTRACT FROM AUTHOR]

In response to the need for approaches to understand how citizen science is currently influencing environmental policy and associated decision making, we devised the Citizen Science Impact StoryTelling Approach (CSISTA). We iteratively designed instruments to be used as tools primarily for citizen science practitioners seeking to understand or communicate policy impacts. We then trialled the CSISTA and associated instruments on four exemplary citizen science initiatives, using different forms of inquiry and collaboration with respective initiative leaders. In this paper, we present CSISTA, with details of the steps for implementing inquiry and storytelling instruments. Additionally, we reflect on insights gained and challenges encountered implementing the approach. Overall, we found the versatility and structure of CSISTA as a process with multiple guiding instruments useful. We envision the approach being helpful, particularly with regards to: 1) gaining an understanding of a citizen science initiative's policy and decision-making impacts; 2) creating short policy impact stories to communicate such impacts to broader audiences; or 3) fulfilling both goals to understand and communicate policy impacts with a unified approach. We encourage others to explore, adapt, and improve the approach. Additionally, we hope that explorations of CSISTA will foster broader discussions on how to understand and strengthen interactions between citizen science practitioners, policy makers, and decision makers at large, whether at local, national, or international scales. • Need to understand how citizen science influences environmental policy. • Need to know how to communicate with policy makers and other stakeholders. • The CSISTA approach supports citizen science leaders. • The tools can help understand or communicate their policy impacts. • Impact stories can demonstrate the value of citizen science to policy makers. [ABSTRACT FROM AUTHOR]