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Scientists invent method to extract gold from liquid waste
The next gold rush might take place in our sewers.
- Even though we think of it as exceedingly rare, gold can be found all around us.
- The trouble is, most of the gold is hard to get at; its too diluted in our waste or ocean waters to effectively extract.
- This new technique quickly, easily, and reliably extracts gold from most liquids.
Even though the thought of gold calls to mind incredible wealth hidden underground or horded away in Fort Knox, you can actually find the stuff all over the place. there's gold in nearly every kind of consumer electronic, gold in our sewage, gold in the cracks of New York City sidewalks, and even trace amounts in our brains. The trouble isn't that gold is rare, per se, it's just hard to get to.
In human history, we've mined about 190,000 tons of gold out of the ground. If you want to visualize that amount, it would fit in a box about 20 m on each side; not all that much in the grand scheme of things. We've been able to get at this because it was stored in a way that's relatively easy for us to access. It was buried in the Earth, so we just had to dig it up. In contrast, we've estimated that there's about 20 million tons of gold in the ocean—it's just distributed throughout the seas, making it difficult to refine and extract.
In the past, we didn't use gold for much of anything besides as a method to store value, so the fact that most gold on Earth was inaccessible was more of a feature than a bug. But now, we're increasingly finding practical applications for the precious metal. It can be used in medicine to treat arthritis or for dentistry; it's an excellent conductor, so it can be used in electronics and communication technology; and it reflects infrared radiation, so we use it on our spacecraft and spacesuits. Suddenly, getting at those 20 million tons of gold in the ocean and elsewhere on Earth has become more about technological and societal progress than about accumulating wealth.
New research from the Journal of the American Chemical Society has uncovered one of the most effective methods to date to extract gold from liquids. That includes electronic waste, sewage, ocean water, waste water—almost any liquid where we might find gold. Just to highlight how potentially useful this is, sewage from Switzerland alone is estimated to carry away 1.8 million dollars' worth of gold every year.
Making a sponge for gold
The object to the left shows the basic framework, a lattice of iron ion clusters connected by organic molecules. On this structure, a polymer that helps catch gold is coated, represented by the purple dots.
Sun et al. 2018
The method consists of a metal-organic framework—essentially, clusters metal ions connected by an organic "skeleton." In this case, the framework consists of iron ions connected by an organic compound called 1,3,5-benzenetricarboxylate. The researchers then coated this structure in a polymer with an even more difficult-to-pronounce name (for the curious, it's poly-para-phenylenediamine, or PpDA), which helps the framework catch stray molecules of gold.
Essentially, the framework and polymer work as a very granular sponge, only this sponge doesn't hold soap or water; instead, it holds gold.
Other researchers have built structures like this one before, but the new framework works exceptionally well. For every gram of this gold-seeking sponge submerged in a liquid, it can hold up to a gram of gold. What's more, it can catch 99% of the gold in a given solution in as little as two minutes.
Once the framework's sucked up the gold, it can easily be destroyed to retrieve the gold captured inside. The figure below shows how this works. After it's been suspended in a gold-containing solution, the framework is dissolved in hydrochloric acid. After some time, all that's left is 23.9 K gold, which is the highest purity of gold reclaimed from similar projects.
On the left, a sample of liquid is shown with the new material suspended inside. After the material is dissolved in acid, 23.9 K gold particles are leftover. On the right side, the gold particles are shown under a microscope.
Sun et al. 2018
The researchers tested the method out in a few different real-world cases. One of the most useful applications for a method like this is in reclaiming gold from electronic waste. It can take as much as a ton of gold ore to build just 40 smartphones, so getting the gold out of electronic waste would be extremely practical.
The researchers physically removed the metal from a CPU and treated it with some chemicals to form a solution. In the figure below, you can see that this produced a blue solution. So far, this technique is nothing new. The trouble is that a CPU also contains copper and nickel as well as gold, all of which is mixed up in this solution. So, the trick is how to get the really valuable metal out of the mixture. Using the new method, the researchers managed to get 95% of the gold out of the solution.
The top-left image shows a regular CPU. To its right, we can see the various elements that comprise the CPU (copper, nickel, and gold). In the bottom-left corner, we can see the CPU after its material has been physically removed. The image to its right shows the material dissolved into a blue solution and a graph showing how much of each material the new method recovered from the solution.
Sun et al. 2018
They found similar results with different liquids, too. The new framework captured 99% of gold from Swiss sewage (which, if you'll recall, allegedly washes away $1.8 million worth of gold every year). The researchers also tried extracting gold from seawater, and, once again, they were able to extract 99% of gold from their sample. These last two examples are especially promising; sewage and seawater contain a huge variety of different compounds that could interfere with any kind of filtering system.
We're still a long way off from, say, filtering the oceans for the precious metals they contain. But as we continue to use up the easily accessible resources buried in the Earth, exploring new techniques like this will be important if we want to continue to use smartphones, explore space, and collectively advance as a society.
"You dream about these kinds of moments when you're a kid," said lead paleontologist David Schmidt.
- The triceratops skull was first discovered in 2019, but was excavated over the summer of 2020.
- It was discovered in the South Dakota Badlands, an area where the Triceratops roamed some 66 million years ago.
- Studying dinosaurs helps scientists better understand the evolution of all life on Earth.
David Schmidt, a geology professor at Westminster College, had just arrived in the South Dakota Badlands in summer 2019 with a group of students for a fossil dig when he received a call from the National Forest Service. A nearby rancher had discovered a strange object poking out of the ground. They wanted Schmidt to take a look.
"One of the very first bones that we saw in the rock was this long cylindrical bone," Schmidt told St. Louis Public Radio. "The first thing that came out of our mouths was, 'That kind of looks like the horn of a triceratops.'"
After authorities gave the go-ahead, Schmidt and a small group of students returned this summer and spent nearly every day of June and July excavating the skull.
Credit: David Schmidt / Westminster College
"We had to be really careful," Schmidt told St. Louis Public Radio. "We couldn't disturb anything at all, because at that point, it was under law enforcement investigation. They were telling us, 'Don't even make footprints,' and I was thinking, 'How are we supposed to do that?'"
Another difficulty was the mammoth size of the skull: about 7 feet long and more than 3,000 pounds. (For context, the largest triceratops skull ever unearthed was about 8.2 feet long.) The skull of Schmidt's dinosaur was likely a Triceratops prorsus, one of two species of triceratops that roamed what's now North America about 66 million years ago.
Credit: David Schmidt / Westminster College
The triceratops was an herbivore, but it was also a favorite meal of the Tyrannosaurus rex. That probably explains why the Dakotas contain many scattered triceratops bone fragments, and, less commonly, complete bones and skulls. In summer 2019, for example, a separate team on a dig in North Dakota made headlines after unearthing a complete triceratops skull that measured five feet in length.
Michael Kjelland, a biology professor who participated in that excavation, said digging up the dinosaur was like completing a "multi-piece, 3-D jigsaw puzzle" that required "engineering that rivaled SpaceX," he jokingly told the New York Times.
Morrison Formation in Colorado
James St. John via Flickr
The Badlands aren't the only spot in North America where paleontologists have found dinosaurs. In the 1870s, Colorado and Wyoming became the first sites of dinosaur discoveries in the U.S., ushering in an era of public fascination with the prehistoric creatures — and a competitive rush to unearth them.
Since, dinosaur bones have been found in 35 states. One of the most fruitful locations for paleontologists has been the Morrison formation, a sequence of Upper Jurassic sedimentary rock that stretches under the Western part of the country. Discovered here were species like Camarasaurus, Diplodocus, Apatosaurus, Stegosaurus, and Allosaurus, to name a few.
|Credit: Nobu Tamura/Wikimedia Commons|
As for "Shady" (the nickname of the South Dakota triceratops), Schmidt and his team have safely transported it to the Westminster campus. They hope to raise funds for restoration, and to return to South Dakota in search of more bones that once belonged to the triceratops.
Studying dinosaurs helps scientists gain a more complete understanding of our evolution, illuminating a through-line that extends from "deep time" to present day. For scientists like Schmidt, there's also the simple joy of coming to face-to-face with a lost world.
"You dream about these kinds of moments when you're a kid," Schmidt told St. Louis Public Radio. "You don't ever think that these things will ever happen."
A team of scientists managed to install onto a smartphone a spectrometer that's capable of identifying specific molecules — with cheap parts you can buy online.
- Spectroscopy provides a non-invasive way to study the chemical composition of matter.
- These techniques analyze the unique ways light interacts with certain materials.
- If spectrometers become a common feature of smartphones, it could someday potentially allow anyone to identify pathogens, detect impurities in food, and verify the authenticity of valuable minerals.
The quality of smartphone cameras has increased exponentially over the past decade. Today's smartphone cameras can not only capture photos that rival those of stand-alone camera systems but also offer practical applications, like heart-rate measurement, foreign-text translation, and augmented reality.
What's the next major functionality of smartphone cameras? It could be the ability to identify chemicals, drugs, and biological molecules, according to a new study published in the Review of Scientific Instruments.
The study describes how a team of scientists at Texas A&M turned a common smartphone into a "pocket-sized" Raman and emission spectral detector by modifying it with just $50 worth of extra equipment. With the added hardware, the smartphone was able to identify chemicals in the field within minutes.
The technology could have a wide range of applications, including diagnosing certain diseases, detecting the presence of pathogens and dangerous chemicals, identifying impurities in food, and verifying the authenticity of valuable artwork and minerals.
Raman and fluorescence spectroscopy
Raman and fluorescence spectroscopies are techniques for discerning the chemical composition of materials. Both strategies exploit the fact that light interacts with certain types of matter in unique ways. But there are some differences between the two techniques.
As the name suggests, fluorescence spectroscopy measures the fluorescence — that is, the light emitted by a substance when it absorbs light or other electromagnetic radiation — of a given material. It works by shining light on a material, which excites the electrons within the molecules of the material. The electrons then emit fluorescent light toward a filter that measures fluorescence.
The particular spectra of fluorescent light that's emitted can help scientists detect small concentrations of particular types of biological molecules within a material. But some biomolecules, such as RNA and DNA, don't emit fluorescent light, or they only do so at extremely low levels. That's where Raman spectroscopy comes into play.
Raman spectroscopy involves shooting a laser at a sample and observing how the light scatters. When light hits molecules, the atoms within the molecules vibrate and photons get scattered. Most of the scattered light is of the same wavelength and color as the original light, so it provides no information. But a tiny fraction of the light gets scattered differently; that is, the wavelength and color are different. Known as Raman scattering, this is extremely useful because it provides highly precise information about the chemical composition of the molecule. In other words, all molecules have a unique Raman "fingerprint."
Creating an affordable, pocket-sized spectrometer
To build the spectrometer, the researchers connected a smartphone to a laser and a series of plastic lenses. The smartphone camera was placed facing a transmission diffraction grating, which splits incoming light into its constituent wavelengths and colors. After a laser is fired into a sample, the scattered light is diffracted through this grating, and the smartphone camera analyzes the light on the other side.
Schematic diagram of the designed system.Credit: Dhankhar et al.
To test the spectrometer, the researchers analyzed a range of sample materials, including carrots and bacteria. The laser used in the spectrometer emits a wavelength that's readily absorbed by the pigments in carrots and bacteria, which is why these materials were chosen.
The results showed that the smartphone spectrometer was able to correctly identify the materials, but it wasn't quite as effective as the best commercially available Raman spectrometers. The researchers noted that their system might be improved by using specific High Dynamic Range (HDR) smartphone camera applications.
Ultimately, the study highlights how improving the fundamentals of a technology, like smartphone cameras, can lead to a surprisingly wide range of useful applications.
"This inexpensive yet accurate recording pocket Raman system has the potential of being an integral part of ubiquitous cell phones that will make it possible to identify chemical impurities and pathogens, in situ within minutes," the researchers concluded.
- Lawrence Kohlberg's experiments gave children a series of moral dilemmas to test how they differed in their responses across various ages.
- He identified three separate stages of moral development from the egoist to the principled person.
- Some people do not progress through all the stages of moral development, which means they will remain "morally undeveloped."
Has your sense of right and wrong changed over the years? Are there things that you see as acceptable today that you'd never dream of doing when you were younger? If you spend time around children, do you notice how starkly different their sense of morality is? How black and white, or egocentric, or oddly rational it can be?
These were questions that Lawrence Kohlberg asked, and his "stages of moral development" dominates a lot of moral psychology today.
The Heinz Dilemma
Kohlberg was curious to see how and why children differed in their ethical judgements, and so he gave roughly 60 children, across a variety of ages, a series of moral dilemmas. They were all given open-ended questions to explain their answers in order to minimize the risk of leading them to a certain response.
For instance, one of the better-known dilemmas involved an old man called Heinz who needed an expensive drug for his dying wife. Heinz only managed to raise half the required money, which the pharmacists wouldn't accept. Unable to afford it, he has only three options. What should he do?
(a) Not steal it because it's breaking the law.
(b) Steal it, and go to jail for breaking the law.
(c) Steal it, but be let off a prison sentence.
What option would you choose?
Stages of Moral Development
From the answers he got, Kohlberg identified three definite levels or stages of our moral development.
Pre-conventional stage. This is characterized by an ego-centric attitude that seeks pleasure and to prevent pain. The primary motivation is to avoid punishment or claim a reward. In this stage of moral development, "good" is defined as whatever is beneficial to oneself. "Bad" is the opposite. For instance, a young child might share their food with a younger sibling not from kindness or some altruistic impulse but because they know that they'll be praised by their parents (or, perhaps, have their food taken away from them).
In the pre-conventional stage, there is no inherent sense of right and wrong, per se, but rather "good" is associated with reward and "bad" is associated with punishment. At this stage, children are sort of like puppies.
If you spend time around children, do you notice how starkly different their sense of morality is? How black and white, or egocentric, or oddly rational it can be?
Conventional stage. This stage reflects a growing sense of social belonging and hence a higher regard for others. Approval and praise are seen as rewards, and behavior is calibrated to please others, obey the law, and promote the good of the family/tribe/nation. In the conventional stage, a person comes to see themselves as part of a community and that their actions have consequences.
Consequently, this stage is much more rule-focused and comes along with a desire to be seen as good. Image, reputation, and prestige matter the most in motivating good behavior — we want to fit into our community.
Post-conventional stage. In this final stage, there is much more self-reflection and moral reasoning, which gives people the capacity to challenge authority. Committing to principles is considered more important than blindly obeying fixed laws. Importantly, a person comes to understand the difference between what is "legal" and what is "right." Ideas such as justice and fairness start to mature. Laws or rules are no longer equated to morality but might be seen as imperfect manifestations of larger principles.
A lot of moral philosophy is only possible in the post-conventional stage. Theories like utilitarianism or Immanuel Kant's duty-focused ethics ask us to consider what's right or wrong in itself, not just because we get a reward or look good to others. Aristotle perhaps sums it up best when he wrote, "I have gained this from philosophy: that I do without being commanded what others do only from fear of the law."
How morally developed are you?
Kohlberg identified these stages as a developmental progression from early infancy all the way to adulthood, and they map almost perfectly onto Jean Piaget's psychology of child development. For instance, the pre-conventional stage usually lasts from birth to roughly nine years old, the conventional occurs mainly during adolescence, and the post-conventional goes into adulthood.
What's important to note, though, is that this is not a fatalistic timetable to which all humans adhere. Kohlberg thought, for instance, that some people never progress or mature. It's quite possible, maybe, for someone to have no actual moral compass at all (which is sometimes associated with psychopathy).
More commonly, though, we all know people who are resolutely bound to the conventional stage, where they care only for their image or others' judgment. Those who do not develop beyond this stage are usually stubbornly, even aggressively, strict in following the rules or the law. Prepubescent children can be positively authoritarian when it comes to obeying the rules of a board game, for instance.
So, what's your answer to the Heinz dilemma? Where do you fall on Kohlberg's moral development scale? Is he right to view it is a progressive, hierarchical maturing, where we have "better" and "worse" stages? Or could it be that as we grow older, we grow more immoral?
Dunbar's number is a popular estimate for the maximum size of social groups. But new research suggests that it's a fictitious number based on flimsy data and bad theory.