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L’investiture de Trump soulève 2 dangers pour le climat

21 janvier 2025 à 11:02

Ce 20 janvier 2025, Donald Trump a annoncé quitter de nouveau l'Accord de Paris et favoriser la production énergétique à partir du pétrole et du gaz aux États-Unis.

Savez-vous que ces voitures sont interdites sur les routes françaises depuis le 1er janvier 2025 ?

21 janvier 2025 à 10:46
Une Hp 2025 01 21t104611.792

Depuis le 1er janvier 2025, de nouvelles restrictions de circulation sont entrées en vigueur dans plusieurs grandes villes françaises, principalement dans le cadre des Zones à Faibles Émissions (ZFE). Ces mesures visent à améliorer la qualité de l'air en limitant la circulation des véhicules les plus polluants. Les propriétaires de véhicules classés Crit'Air 3 seront particulièrement concernés par ces changements.

Savez-vous que ces voitures sont interdites sur les routes françaises depuis le 1er janvier 2025 ?

21 janvier 2025 à 10:46
Une Hp 2025 01 21t104611.792

Depuis le 1er janvier 2025, de nouvelles restrictions de circulation sont entrées en vigueur dans plusieurs grandes villes françaises, principalement dans le cadre des Zones à Faibles Émissions (ZFE). Ces mesures visent à améliorer la qualité de l'air en limitant la circulation des véhicules les plus polluants. Les propriétaires de véhicules classés Crit'Air 3 seront particulièrement concernés par ces changements.

Et si l’IA causait la prochaine pénurie d’énergie ? Les chiffres inquiétants du MIT

L’utilisation de l’intelligence artificielle (IA) explose et certains s’inquiètent des bouleversements sur la société et des risques de sécurité. Le MIT s’est penché sur une autre facette de cette révolution, moins prise en compte : son impact sur l’environnement.

Supramolecular biomass foam removes microplastics from water

23 décembre 2024 à 15:00

A reusable and biodegradable fibrous foam developed by researchers at Wuhan University in China can remove up to 99.8% of microplastics from polluted water. The foam, which is made from a self-assembled network of chitin and cellulose obtained from biomass wastes, has been successfully field-tested in four natural aquatic environments.

The amount of plastic waste in the environment has reached staggering levels and is now estimated at several billion metric tons. This plastic degrades extremely slowly and poses a hazard for ecosystems throughout its lifetime. Aquatic life is particularly vulnerable, as micron-sized plastic particles can combine with other pollutants in water and be ingested by a wide range of organisms. Removing these microplastic particles would help limit the damage, but standard filtration technologies are ineffective as the particles are so small.

A highly porous interconnected structure

The new adsorbent developed by Wuhan’s Hongbing Deng and colleagues consists of intertwined beta-chitin nanofibre sheets (obtained from squid bone) with protonated amines and suspended cellulose fibres (obtained from cotton). This structure contains a number of functional groups, including -OH, -NH3+ and -NHCO- that allow the structure to self-assemble into a highly porous interconnected network.

This self-assembly is important, Deng explains, because it means the foam does not require “complex processing (no cross-linking and minimal use of chemical reagents) or adulteration with toxic or expensive substances,” he tells Physics World.

The functional groups make the surface of the foam rough and positively charged, providing numerous sites that can interact and adsorb plastic particles ranging in size from less than 100 nm to over 1000 microns. Deng explains that multiple mechanisms are at work during this process, including physical interception, electrostatic attraction and intermolecular interactions. The latter group includes interactions that involv hydrogen bonding, van der Waals forces and weak hydrogen bonding interactions (between OH and CH groups, for example).

The researchers tested their foam in lake water, coastal water, still water (a small pond) and water used for agricultural irrigation. They also combined these systematic adsorption experiments with molecular dynamics (MD) simulations and Hirshfeld partition (IGMH) calculations to better understand how the foam was working.

They found that the foam can adsorb a variety of nanoplastics and microplastics, including the polystyrene, polymethyl methacrylate, polypropylene and polyethylene terephthalate found in everyday objects such as electronic components, food packaging and textiles. Importantly, the foam can adsorb these plastics even in water bodies polluted with toxic metals such as lead and chemical dyes. It adsorbed nearly 100% of the particles in its first cycle and around 96-98% of the particles over the following five cycles.

“The great potential of biomass”

Because the raw materials needed to make the foam are readily available, and the fabrication process is straightforward, Deng thinks it could be produced on a large scale. “Other microplastic removal materials made from biomass feedstocks have been reported in recent years, but some of these needed to be functionalized with other chemicals,” he says. “Such treatments can increase costs or hinder their large-scale production.”

 Deng and his team have applied for a patent on the material and are now looking for industrial partners to help them produce it. In the meantime, he hopes the work will help draw attention to the microplastic problem and convince more scientists to work on it. “We believe that the great potential of biomass will be recognized and that the use of biomass resources will become more diverse and thorough,” he says.

The present work is described in Science Advances.

The post Supramolecular biomass foam removes microplastics from water appeared first on Physics World.

Eco-friendly graphene composite recovers gold from e-waste

24 octobre 2024 à 11:55

A new type of composite material is 10 times more efficient at extracting gold from electronic waste than previous adsorbents. Developed by researchers in Singapore, the UK and China, the environmentally-friendly composite is made from graphene oxide and a natural biopolymer called chitosan, and it filters the gold without an external power source, making it an attractive alternative to older, more energy-intensive techniques.

Getting better at extracting gold from electronic waste, or e-waste, is desirable for two reasons. As well as reducing the volume of e-waste, it would lessen our reliance on mining and refining new gold, which involves environmentally hazardous materials such as activated carbon and cyanides. Electronic waste management is a relatively new field, however, and existing techniques like electrolysis are time-consuming and require a lot of energy.

A more efficient and suitable recovery process

Led by Kostya Novoselov and Daria Andreeva of the Institute for Functional Intelligent Materials at the National University of Singapore, the researchers chose graphene and chitosan because both have desirable characteristics for gold extraction. Graphene boasts a high surface area, making it ideal for adsorbing ions, they explain, while chitosan acts as a natural reducing agent, catalytically converting ionic gold into its solid metallic form.

While neither material is efficient enough to compete with conventional methods such as activated carbon on its own, Andreeva says they work well together. “By combining both of them, we enhance both the adsorption capacity of graphene and the catalytic reduction ability of chitosan,” she explains. “The result is a more efficient and suitable gold recovery process.”

High extraction efficiency

The researchers made the composite by getting one-dimensional chitosan macromolecules to self-assemble on two-dimensional flakes of graphene oxide. This assembly process triggers the formation of sites that bind gold ions. The enhanced extracting ability of the composite comes from the fact that the ion binding is cooperative, meaning that an ion binding at one site allows other ions to bind, too. The team had previously used similar methods in studies that focused on structures such as novel membranes with artificial ionic channels, anticorrosion coatings, sensors and actuators, switchable water valves and bioelectrochemical systems.

Once the gold ions are adsorbed onto the graphene surface, the chitosan catalyses the reduction of these ions, converting them from their ionic state into solid metallic gold, Andreeva explains. “This combined action of adsorption and reduction makes the process both highly efficient and environmentally friendly, as it avoids the use of harsh chemicals typically employed in gold recovery from electronic waste,” she says.

The researchers tested the material on a real waste mixture provided by SG Recycle Group SG3R, Pte, Ltd. Using this mixture, which contained gold in a residual concentration of just 3 ppm, they showed that the composite can extract nearly 17g/g of Au3+ ions and just over 6 g/g of Au+ from a solution – values that are 10 times larger than existing gold adsorbents. The material also has an extraction efficiency of above 99.5 percent by weight (wt%), breaking the current of limit of 75 wt%. To top it off, the ion extraction process is ultrafast, taking around just 10 minutes compared to days for other graphene-based adsorbents.

No applied voltage required

The researchers, who report their work in PNAS, say that the multidimensional architecture of the composite’s structure means that no applied voltage is required to adsorb and reduce gold ions. Instead, the technique relies solely on the chemisorption kinetics of gold ions on the heterogenous graphene oxide/chitosan nanoconfinement channels and the chemical reduction at multiple binding sites. The new process therefore offers a cleaner, more efficient and environmentally-friendly method for recovering gold from electronic waste, they add.

While the present work focused on gold, the team say the technique could be adapted to recover other valuable metals such as silver, platinum or palladium from electronic waste or even mining residues. And that is not all: as well as e-waste, the technology might be applied to a wider range of environmental cleaning efforts, such as filtering out heavy metals from polluted water sources or industrial effluents. “It thus provides a solution for reducing metal contamination in ecosystems,” Andreeva says.

Other possible applications areas, she adds, include sustainable decarbonization and hydrogen production, low-dimensional building blocks for embedding artificial neural networks in hardware for neuromorphic computing and biomedical applications.

The Singapore researchers are now studying how to regenerate and reuse the composite material itself, to further reduce waste and improve the process’s sustainability. “Our ongoing research is focusing on optimizing the material’s properties, bringing us closer to a scalable, eco-friendly solution for e-waste management and beyond,” Andreeva says.

The post Eco-friendly graphene composite recovers gold from e-waste appeared first on Physics World.

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