Category: The Conversation – in French

Source: The Conversation – Canada – By Justin M. Chalker, Professor of Chemistry, Flinders University

In 2022, humans produced an estimated 62 million tonnes of electronic waste – enough to fill more than 1.5 million garbage trucks. This was up 82% from 2010 and is expected to rise to 82 million tonnes in 2030.

This e-waste includes old laptops and phones, which contain precious materials such as gold. Less than one quarter of it is properly collected and recycled. But a new technique colleagues and I have developed to safely and sustainably extract gold from e-waste could help change that.

Our new gold-extraction technique, which we describe in a new paper published today in Nature Sustainability, could also make small-scale gold mining less poisonous for people – and the planet.

Soaring global demand

Gold has long played a crucial role in human life. It has been a form of currency and a medium for art and fashion for centuries. Gold is also essential in modern industries including the electronics, chemical manufacture and aerospace sectors.

But while global demand for this precious metal is soaring, mining it is harmful to the environment.

Deforestation and use of toxic chemicals are two such problems. In formal, large-scale mining, highly toxic cyanide is widely used to extract gold from ore. While cyanide can be degraded, its use can cause harm to wildlife, and tailings dams which store the toxic byproducts of mining operations pose a risk to the wider environment.

In small-scale and artisanal mining, mercury is used extensively to extract gold. In this practice, the gold reacts with mercury to form a dense amalgam that can be easily isolated. The gold is then recovered by heating the amalgam to vaporise the mercury.

Small-scale and artisanal mining is the largest source of mercury pollution on Earth, and the mercury emissions are dangerous to the miners and pollute the environment. New methods are required to reduce the impacts of gold mining.

A safer alternative

Our interdisciplinary team of scientists and engineers has developed a new technique to extract gold from ore and e-waste. The aim was to provide a safer alternative to mercury and cyanide and reduce the health and environmental impacts of gold mining.

Many techniques have previously been reported for extracting gold from ore or e-waste, including mercury- and cyanide-free methods. However, many of these methods are limited in rate, yield, scale and cost. Often these methods also consider only one step in the entire gold recovery process, and recycling and waste management is often neglected.

In contrast, our approach considered sustainability throughout the whole process of gold extraction, recovery and refining. Our new leaching technology uses a chemical commonly used in water sanitation and pool chlorination: trichloroisocyanuric acid.

When this widely available and low-cost chemical is activated with salt water, it can react with gold and convert it into a water-soluble form.

To recover the gold from the solution, we invented a sulphur-rich polymer sorbent. Polymer sorbents isolate a certain substance from a liquid or gas, and ours is made by joining a key building block (a monomer) together through a chain reaction.

Our polymer sorbent is interesting because it is derived from elemental sulphur: a low-cost and highly abundant feedstock. The petroleum sector generates more sulphur than it can use or sell, so our polymer synthesis is a new use for this underused resource.

Our polymer could selectively bind and remove gold from the solution, even when many other types of metals were present in the mixture.

The simple leaching and recovery methods were demonstrated on ore, circuit boards from obsolete computers and scientific waste. Importantly, we also developed methods to regenerate and recycle both the leaching chemical and the polymer sorbent. We also established methods to purify and recycle the water used in the process.

In developing the recyclable polymer sorbent, we invented some exciting new chemistry to make the polymer using light, and then “un-make” the sorbent after it bound gold. This recycling method converted the polymer back to its original monomer building block and separated it from the gold.

The recovered monomer could then be re-made into the gold-binding polymer: an important demonstration of how the process is aligned with a circular economy.

A long and complex road ahead

In future work, we plan to collaborate with industry, government and not-for-profit groups to test our method in small-scale mining operations. Our long-term aim is to provide a robust and safe method for extracting gold, eliminating the need for highly toxic chemicals such as cyanide and mercury.

There will be many challenges to overcome including scaling up the production of the polymer sorbent and the chemical recycling processes. For uptake, we also need to ensure that the rate, yield and cost are competitive with more traditional methods of gold mining. Our preliminary results are encouraging. But there is still a long and complex road ahead before our new techniques replace cyanide and mercury.

Our broader motivation is to support the livelihood of the millions of artisanal and small-scale miners that rely on mercury to recover gold.

They typically operate in remote and rural regions with few other economic opportunities. Our goal is to support these miners economically while offering safer alternatives to mercury. Likewise, the rise of “urban mining” and e-waste recycling would benefit from safer and operationally simple methods for precious metal recovery.

Success in recovering gold from e-waste will also reduce the need for primary mining and therefore lessen its environmental impact.

Justin M. Chalker is an inventor on patents associated with the gold leaching and recovery technology. Both patents are wholly owned by Flinders University. This research was supported financially by the Australian Research Council and Flinders University. He has an ongoing collaboration with Mercury Free Mining and Adelaide Control Engineering: organisations that supported the developments and trials reported in this study.

– ref. There’s gold trapped in your iPhone – and chemists have found a safe new way to extract it – https://theconversation.com/theres-gold-trapped-in-your-iphone-and-chemists-have-found-a-safe-new-way-to-extract-it-259817

Source: The Conversation – Canada – By Hassan Vally, Associate Professor, Epidemiology, Deakin University

We all like to imagine we’re ageing well. Now a simple blood or saliva test promises to tell us by measuring our “biological age”. And then, as many have done, we can share how “young” we really are on social media, along with our secrets to success.

While chronological age is how long you have been alive, measures of biological age aim to indicate how old your body actually is, purporting to measure “wear and tear” at a molecular level.

The appeal of these tests is undeniable. Health-conscious consumers may see their results as reinforcing their anti-ageing efforts, or a way to show their journey to better health is paying off.

But how good are these tests? Do they actually offer useful insights? Or are they just clever marketing dressed up to look like science?

How do these tests work?

Over time, the chemical processes that allow our body to function, known as our “metabolic activity”, lead to damage and a decline in the activity of our cells, tissues and organs.

Biological age tests aim to capture some of these changes, offering a snapshot of how well, or how poorly, we are ageing on a cellular level.

Our DNA is also affected by the ageing process. In particular, chemical tags (methyl groups) attach to our DNA and affect gene expression. These changes occur in predictable ways with age and environmental exposures, in a process called methylation.

Research studies have used “epigenetic clocks”, which measure the methylation of our genes, to estimate biological age. By analysing methylation levels at specific sites in the genome from participant samples, researchers apply predictive models to estimate the cumulative wear and tear on the body.

What does the research say about their use?

Although the science is rapidly evolving, the evidence underpinning the use of epigenetic clocks to measure biological ageing in research studies is strong.

Studies have shown epigenetic biological age estimation is a better predictor of the risk of death and ageing-related diseases than chronological age.

Epigenetic clocks also have been found to correlate strongly with lifestyle and environmental exposures, such as smoking status and diet quality.

In addition, they have been found to be able to predict the risk of conditions such as cardiovascular disease, which can lead to heart attacks and strokes.

Taken together, a growing body of research indicates that at a population level, epigenetic clocks are robust measures of biological ageing and are strongly linked to the risk of disease and death

But how good are these tests for individuals?

While these tests are valuable when studying populations in research settings, using epigenetic clocks to measure the biological age of individuals is a different matter and requires scrutiny.

For testing at an individual level, perhaps the most important consideration is the “signal to noise ratio” (or precision) of these tests. This is the question of whether a single sample from an individual may yield widely differing results.

A study from 2022 found samples deviated by up to nine years. So an identical sample from a 40-year-old may indicate a biological age of as low as 35 years (a cause for celebration) or as high as 44 years (a cause of anxiety).

While there have been significant improvements in these tests over the years, there is considerable variability in the precision of these tests between commercial providers. So depending on who you send your sample to, your estimated biological age may vary considerably.

Another limitation is there is currently no standardisation of methods for this testing. Commercial providers perform these tests in different ways and have different algorithms for estimating biological age from the data.

As you would expect for commercial operators, providers don’t disclose their methods. So it’s difficult to compare companies and determine who provides the most accurate results – and what you’re getting for your money.

A third limitation is that while epigenetic clocks correlate well with ageing, they are simply a “proxy” and are not a diagnostic tool.

In other words, they may provide a general indication of ageing at a cellular level. But they don’t offer any specific insights about what the issue may be if someone is found to be “ageing faster” than they would like, or what they’re doing right if they are “ageing well”.

So regardless of the result of your test, all you’re likely to get from the commercial provider of an epigenetic test is generic advice about what the science says is healthy behaviour.

Are they worth it? Or what should I do instead?

While companies offering these tests may have good intentions, remember their ultimate goal is to sell you these tests and make a profit. And at a cost of around A$500, they’re not cheap.

While the idea of using these tests as a personalised health tool has potential, it is clear that we are not there yet.

For this to become a reality, tests will need to become more reproducible, standardised across providers, and validated through long-term studies that link changes in biological age to specific behaviours.

So while one-off tests of biological age make for impressive social media posts, for most people they represent a significant cost and offer limited real value.

The good news is we already know what we need to do to increase our chances of living longer and healthier lives. These include:

• improving our diet
• increasing physical activity
• getting enough sleep
• quitting smoking
• reducing stress
• prioritising social connection.

We don’t need to know our biological age in order to implement changes in our lives right now to improve our health.

Hassan Vally does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. How old are you really? Are the latest ‘biological age’ tests all they’re cracked up to be? – https://theconversation.com/how-old-are-you-really-are-the-latest-biological-age-tests-all-theyre-cracked-up-to-be-257710

Source: The Conversation – Canada – By Nicholas Wu, Lecturer in Wildlife Ecology, Murdoch University

Bats are often cast as the unseen night-time stewards of nature, flitting through the dark to control pest insects, pollinate plants and disperse seeds. But behind their silent contributions lies a remarkable and underappreciated survival strategy: seasonal fattening.

Much like bears and squirrels, bats around the world bulk up to get through hard times – even in places where you might not expect it.

In a paper published today in Ecology Letters, we analysed data from bat studies around the world to understand how bats use body fat to survive seasonal challenges, whether it’s a freezing winter or a dry spell.

The surprising conclusion? Seasonal fattening is a global phenomenon in bats, not just limited to those in cold climates.

Even bats in the tropics, where it’s warm all year, store fat in anticipation of dry seasons when food becomes scarce. That’s a survival strategy that’s been largely overlooked. But it may be faltering as the climate changes, putting entire food webs at risk.

Climate shapes fattening strategies

We found bats in colder regions predictably gain more weight before winter.

But in warmer regions with highly seasonal rainfall, such as tropical savannas or monsoonal forests, bats also fatten up. In tropical areas, it’s not cold that’s the enemy, but the dry season, when flowers wither, insects vanish and energy is hard to come by.

The extent of fattening is impressive. Some species increased their body weight by more than 50%, which is a huge burden for flying animals that already use a lot of energy to move around. This highlights the delicate balancing act bats perform between storing energy and staying nimble in the air.

Sex matters, especially in the cold

The results also support the “thrifty females, frisky males” hypothesis.

In colder climates, female bats used their fat reserves more sparingly than males – a likely adaptation to ensure they have enough energy left to raise young when spring returns. Since females typically emerge from hibernation to raise their young, conserving fat through winter can directly benefit their reproductive success.

Interestingly, this sex-based difference vanished in warmer climates, where fat use by males and females was more similar, likely because more food is available in warmer climates. It’s another clue that climate patterns intricately shape behaviour and physiology.

Climate change is shifting the rules

Beyond the biology, our study points to a more sobering trend. Bats in warm regions appear to be increasing their fat stores over time. This could be an early warning sign of how climate change is affecting their survival.

Climate change isn’t just about rising temperatures. It’s also making seasons more unpredictable.

Bats may be storing more energy in advance of dry seasons that are becoming longer or harder to predict. That’s risky, because it means more foraging, more exposure to predators and potentially greater mortality.

The implications can ripple outward. Bats help regulate insect populations, fertilise crops and maintain healthy ecosystems. If their survival strategies falter, entire food webs could feel the effects.

Fat bats, fragile futures

Our study changes how we think about bats. They are not just passive victims of environmental change but active strategists, finely tuned to seasonal rhythms. Yet their ability to adapt has limits, and those limits are being tested by a rapidly changing world.

By understanding how bats respond to climate, we gain insights into broader ecosystem resilience. We also gain a deeper appreciation for one of nature’s quiet heroes – fattening up, flying through the night and holding ecosystems together, one wingbeat at a time.

Nicholas Wu was the lead author of a funded Australian Research Council Linkage Grant awarded to Christopher Turbill at Western Sydney University.

– ref. Bats get fat to survive hard times. But climate change is threatening their survival strategy – https://theconversation.com/bats-get-fat-to-survive-hard-times-but-climate-change-is-threatening-their-survival-strategy-259560

Source: The Conversation – Canada – By Gemma Sharp, Researcher in Body Image, Eating and Weight Disorders, Monash University

Following a particular diet or exercising a great deal are common and even encouraged in our health and image-conscious culture. With increased awareness of food allergies and other dietary requirements, it’s also not uncommon for someone to restrict or eliminate certain foods.

But these behaviours may also be the sign of an unhealthy relationship with food. You can have a problematic pattern of eating without being diagnosed with an eating disorder.

So, where’s the line? What is disordered eating, and what is an eating disorder?

What is disordered eating?

Disordered eating describes negative attitudes and behaviours towards food and eating that can lead to a disturbed eating pattern.

It can involve:

• dieting

• skipping meals

• avoiding certain food groups

• binge eating

• misusing laxatives and weight-loss medications

• inducing vomiting (sometimes known as purging)

• exercising compulsively.

Disordered eating is the term used when these behaviours are not frequent and/or severe enough to meet an eating disorder diagnosis.

Not everyone who engages in these behaviours will develop an eating disorder. But disordered eating – particularly dieting – usually precedes an eating disorder.

What is an eating disorder?

Eating disorders are complex psychiatric illnesses that can negatively affect a person’s body, mind and social life. They’re characterised by persistent disturbances in how someone thinks, feels and behaves around eating and their bodies.

To make a diagnosis, a qualified health professional will use a combination of standardised questionnaires, as well as more general questioning. These will determine how frequent and severe the behaviours are, and how they affect day-to-day functioning.

Examples of clinical diagnoses include anorexia nervosa, bulimia nervosa, binge eating disorder and avoidant/restrictive food intake disorder.

How common are eating disorders and disordered eating?

The answer can vary quite radically depending on the study and how it defines disordered behaviours and attitudes.

An estimated 8.4% of women and 2.2% of men will develop an eating disorder at some point in their lives. This is most common during adolescence.

Disordered eating is also particularly common in young people with 30% of girls and 17% of boys aged 6–18 years reporting engaging in these behaviours.

Although the research is still emerging, it appears disordered eating and eating disorders are even more common in gender diverse people.

Can we prevent eating disorders?

There is some evidence eating disorder prevention programs that target risk factors – such as dieting and concerns about shape and weight – can be effective to some extent in the short term.

The issue is most of these studies last only a few months. So we can’t determine whether the people involved went on to develop an eating disorder in the longer term.

In addition, most studies have involved girls or women in late high school and university. By this age, eating disorders have usually already emerged. So, this research cannot tell us as much about eating disorder prevention and it also neglects the wide range of people at risk of eating disorders.

Is orthorexia an eating disorder?

In defining the line between eating disorders and disordered eating, orthorexia nervosa is a contentious issue.

The name literally means “proper appetite” and involves a pathological obsession with proper nutrition, characterised by a restrictive diet and rigidly avoiding foods believed to be “unhealthy” or “impure”.

These disordered eating behaviours need to be taken seriously as they can lead to malnourishment, loss of relationships, and overall poor quality of life.

However, orthorexia nervosa is not an official eating disorder in any diagnostic manual.

Additionally, with the popularity of special diets (such as keto or paleo), time-restricted eating, and dietary requirements (for example, gluten-free) it can sometimes be hard to decipher when concerns about diet have become disordered, or may even be an eating disorder.

For example, around 6% of people have a food allergy. Emerging evidence suggests they are also more likely to have restrictive types of eating disorders, such as anorexia nervosa and avoidant/restrictive food intake disorder.

However, following a special diet such as veganism, or having a food allergy, does not automatically lead to disordered eating or an eating disorder.

It is important to recognise people’s different motivations for eating or avoiding certain foods. For example, a vegan may restrict certain food groups due to animal rights concerns, rather than disordered eating symptoms.

What to look out for

If you’re concerned about your own relationship with food or that of a loved one, here are some signs to look out for:

• preoccupation with food and food preparation

• cutting out food groups or skipping meals entirely

• obsession with body weight or shape

• large fluctuations in weight

• compulsive exercise

• mood changes and social withdrawal.

It’s always best to seek help early. But it is never too late to seek help.

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In Australia, if you are experiencing difficulties in your relationships with food and your body, you can contact the Butterfly Foundation’s national helpline on 1800 33 4673 (or via their online chat).

For parents concerned their child might be developing concerning relationships with food, weight and body image, Feed Your Instinct highlights common warning signs, provides useful information about help seeking and can generate a personalised report to take to a health professional.

Gemma Sharp receives funding from an NHMRC Investigator Grant. She is a Professor and the Founding Director and Member of the Consortium for Research in Eating Disorders, a registered charity.

– ref. What’s the difference between an eating disorder and disordered eating? – https://theconversation.com/whats-the-difference-between-an-eating-disorder-and-disordered-eating-256787

Source: The Conversation – Canada – By Kamil Zuber, Senior Industry Research Fellow, Future Industries Institute, University of South Australia

When you buy a new electronic appliance, shoes, medicines or even some food items, you often find a small paper sachet with the warning: “silica gel, do not eat”.

What exactly is it, is it toxic, and can you use it for anything?

The importance of desiccants

That little sachet is a desiccant – a type of material that removes excess moisture from the air.

It’s important during the transport and storage of a wide range of products because we can’t always control the environment. Humid conditions can cause damage through corrosion, decay, the growth of mould and microorganisms.

This is why manufacturers include sachets with desiccants to make sure you receive the goods in pristine condition.

The most common desiccant is silica gel. The small, hard and translucent beads are made of silicon dioxide (like most sands or quartz) – a hydrophilic or water-loving material. Importantly, the beads are porous on the nano-scale, with pore sizes only 15 times larger than the radius of their atoms.

These pores have a capillary effect, meaning they condense and draw moisture into the bead similar to how trees transport water through the channelled structures in wood.

In addition, sponge-like porosity makes their surface area very large. A single gram of silica gel can have an area of up to 700 square metres – almost four tennis courts – making them exceptionally efficient at capturing and storing water.

Is silica gel toxic?

The “do not eat” warning is easily the most prominent text on silica gel sachets.

According to health professionals, most silica beads found in these sachets are non-toxic and don’t present the same risk as silica dust, for example. They mainly pose a choking hazard, which is good enough reason to keep them away from children and pets.

However, if silica gel is accidentally ingested, it’s still recommended to contact health professionals to determine the best course of action.

Some variants of silica gel contain a moisture-sensitive dye. One particular variant, based on cobalt chloride, is blue when the desiccant is dry and turns pink when saturated with moisture. While the dye is toxic, in desiccant pellets it is present only in a small amount – approximately 1% of the total weight.

Desiccants come in other forms, too

Apart from silica gel, a number of other materials are used as moisture absorbers and desiccants. These are zeolites, activated alumina and activated carbon – materials engineered to be highly porous.

Another desiccant type you’ll often see in moisture absorbers for larger areas like pantries or wardrobes is calcium chloride. It typically comes in a box filled with powder or crystals found in most hardware stores, and is a type of salt.

Kitchen salt – sodium chloride – attracts water and easily becomes lumpy. Calcium chloride works in the same way, but has an even stronger hygroscopic effect and “traps” the water through a hydration reaction. Once the salt is saturated, you’ll see liquid separating in the container.

I found something that doesn’t seem to be silica gel – what is it?

Some food items such as tortilla wraps, noodles, beef jerky, and some medicines and vitamins contain slightly different sachets, labelled “oxygen absorbers”.

These small packets don’t contain desiccants. Instead, they have chemical compounds that “scavenge” or bond oxygen.

Their purpose is similar to desiccants – they extend the shelf life of food products and sensitive chemicals such as medicines. But they do so by directly preventing oxidation. When some foods are exposed to oxygen, their chemical composition changes and can lead to decay (apples turning brown when cut is an example of oxidation).

There is a whole range of compounds used as oxygen absorbers. These chemicals have a stronger affinity to oxygen than the protected substance. They range from simple compounds such as iron which “rusts” by using up oxygen, to more complex such as plastic films that work when exposed to light.

Can I reuse a desiccant?

Although desiccants and dehumidifiers are considered disposable, you can relatively easily reuse them.

To “recharge” or dehydrate silica gel, you can place it in an oven at approximately 115–125°C for 2–3 hours, although you shouldn’t do this if it’s in a plastic sachet that could melt in the heat.

Interestingly, due to how they bind water, some desiccants require temperatures well above the boiling point of water to dehydrate (for example, calcium chloride hydrates completely dehydrate at 200°C).

After dehydration, silica gel sachets may be useful for drying small electronic items (like your phone after you accidentally dropped it into water), keeping your camera dry, or preventing your family photos and old films from sticking to each other.

This is a good alternative to the questionable method of using uncooked rice, as silica gel doesn’t decompose and won’t leave starch residues on your things.

Kamil Zuber does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. ‘Do not eat’: what’s in those little desiccant sachets and how do they work? – https://theconversation.com/do-not-eat-whats-in-those-little-desiccant-sachets-and-how-do-they-work-258398