Self-Motivation
David Goggins
Former Navy Seal
Career Development
Bryan Cranston
Actor
Critical Thinking
Liv Boeree
International Poker Champion
Emotional Intelligence
Amaryllis Fox
Former CIA Clandestine Operative
Management
Chris Hadfield
Retired Canadian Astronaut & Author
Learn
from the world's big
thinkers
Start Learning

Scientists invent method to extract gold from liquid waste

The next gold rush might take place in our sewers.

Gold nanoparticles
Shutterstock
  • 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.

Take your career to the next level by raising your EQ

Emotional intelligence is a skill sought by many employers. Here's how to raise yours.

Gear
  • Daniel Goleman's 1995 book Emotional Intelligence catapulted the term into widespread use in the business world.
  • One study found that EQ (emotional intelligence) is the top predictor of performance and accounts for 58% of success across all job types.
  • EQ has been found to increase annual pay by around $29,000 and be present in 90% of top performers.
Keep reading Show less

Just How Much Land Does the Federal Government Own — and Why?

The rough beauty of the American West seems as far as you can get from the polished corridors of power in Washington DC.

Surprising Science

The rough beauty of the American West seems as far as you can get from the polished corridors of power in Washington DC. Until you look at the title to the land. The federal government owns large tracts of the western states: from a low of 29.9% in Montana, already more than the national average, up to a whopping 84.5% in Nevada.

Keep reading Show less

Can VR help us understand layers of oppression?

Researchers are using technology to make visual the complex concepts of racism, as well as its political and social consequences.

Future of Learning
  • Often thought of first as gaming tech, virtual reality has been increasingly used in research as a tool for mimicking real-life scenarios and experiences in a safe and controlled environment.
  • Focusing on issues of oppression and the ripple affect it has throughout America's political, educational, and social systems, Dr. Courtney D. Cogburn of Columbia University School of Social Work and her team developed a VR experience that gives users the opportunity to "walk a mile" in the shoes of a black man as he faces racism at three stages in his life: as a child, during adolescence, and as an adult.
  • Cogburn says that the goal is to show how these "interwoven oppressions" continue to shape the world beyond our individual experiences. "I think the most important and powerful human superpower is critical consciousness," she says. "And that is the ability to think, be aware and think critically about the world and people around you...it's not so much about the interpersonal 'Do I feel bad, do I like you?'—it's more 'Do I see the world as it is? Am I thinking critically about it and engaging it?'"
Keep reading Show less

Russia claims world's first COVID-19 vaccine but skepticism abounds

President Vladimir Putin announces approval of Russia's coronavirus vaccine but scientists warn it may be unsafe.

Russian President Vladimir Putin announced coronavirus vaccine at the Novo-Ogaryovo residence outside Moscow, Russia, Tuesday, Aug. 11, 2020.

Credit: Alexei Nikolsky, Sputnik, Kremlin Pool Photo via AP
Coronavirus
  • Vladimir Putin announced on Tuesday that a COVID-19 vaccine has been approved in Russia.
  • Scientists around the world are worried that the vaccine is unsafe and that Russia fast-tracked the vaccine without performing the necessary phase 3 trials.
  • To date, Russia has had nearly 900,000 registered cases of coronavirus.
  • Keep reading Show less
    Scroll down to load more…
    Quantcast