People have gotten much savvier about computer security in the last decade or so. Most people know that sending a document with sensitive information in it is a no-no, so many people try to redact documents with varying levels of success. A common strategy is to replace text with a black box, but you sometimes see sophisticated users pixelate part of an image or document they want to keep private. If you do this for text, be careful. It is possible to unredact pixelated images through software.
It appears that the algorithm is pretty straightforward. It simply guesses letters, pixelates them, and matches the result. You do have to estimate the size of the pixelation, but that’s usually not very hard to do. The code is built using TypeScript and while the process does require a little manual preparation, there’s nothing that seems very difficult or that couldn’t be automated if you were sufficiently motivated.
You don’t see it as often as you used to, but there have been a slew of legal and government scandals where someone redacted a document by putting a black box over a PDF so it was hidden when printed but the text was still in the document. Older wordprocessors often didn’t really delete text, either, if you knew how to look at the files. The Facebook valuation comes to mind. Not to mention that the National Legal and Policy Center was stung with poor redaction techniques.
Many years ago, I read an article about the new hotness: lithium batteries. The author opened with what he no doubt thought was a clever pop culture reference by saying that the mere mention of lithium would “strike fear in the hearts of Klingons.” It was a weak reference to the fictional “dilithium crystals” of Star Trek fame, and even then I found it a bit cheesy, but I guess he had to lead with something.
Decades later, a deeper understanding of the lore makes it clear that a Klingon’s only fear is death with dishonor, but there is a species here on earth that lives in dread of lithium: CEOs of electric vehicle manufacturing concerns. For them, it’s not the presence of lithium that strikes fear, but the relative absence of it; while it’s the 25th most abundant element in the Earth’s crust, and gigatons are dissolved into the oceans of the world, lithium is very reactive and thus tends to be diffuse, making it difficult to obtain concentrated in the quantities their businesses depend on.
As the electric vehicle and renewable energy markets continue to grow, the need for lithium to manufacture batteries will grow with it, potentially to the point where demand outstrips the mining industry’s production capability. To understand how that imbalance may be possible, we’ll take a look at how lithium is currently mined, as well as examine some new mining techniques that may help fill the coming lithium gap.
A Rocky Start
Although lithium has been known and well-characterized by chemists since the early 1800s, it was only in the middle of the previous century that commercial uses for lithium compounds were identified. The aircraft industry’s demand for stable lubricants resulted in the development of greases made from lithium soaps, and the need for high-performance but lightweight metals led the aluminum industry to employ lithium to improve the Hall-Héroult smelting process. Around the same time, doctors discovered that lithium salts can treat patients with bipolar disorder.
Even with the additional demand of the nascent nuclear industry starting in the 1940s, pretty much all the lithium needed could be supplied from small hard-rock mining operations that exploited deposits of rocks containing large crystals of lithium minerals, like spodumene, petalite, and lepidolite. These three minerals remain in high demand to this day for the production of lithium hydroxide, one of the two main lithium compounds used by industry.
The production of lithium from hard rock mines has a lot in common with other mining and refining methods we’ve discussed in this series. Ore-bearing rocks are blasted out of open-pit mines, scooped up by gigantic loaders, and trucked to a refining plant. There, the rock is reduced in size by a series of crushers and mills until it becomes a fine powder. Water is added to the powder to create a slurry known as pulp, which also contains surfactants and dispersants that make the lithium-containing minerals hydrophobic. In a shallow tank with air pumped through from the bottom, the light lithium forms a froth that floats to the top while the heavier rock particles sink.
After the lithium froth is skimmed off the flotation tank, the extra liquid is filtered off to create a concentrated but impure lithium powder that needs to be refined. The refining process depends a lot on the source minerals and desired end product, but for concentrated spodumene ore, lithium is typically leached out using a combination of sulfuric acid and sodium hydroxide. While this is a direct route with high yields, the acids and bases involved can make it environmentally problematic. Other acid-free leaching processes have been developed as a result, which is said to be the kind of process Tesla is using in their new lithium hydroxide plant being built next to their Texas Gigafactory.
Down in the Brine Mine
As mentioned before, seawater contains something like 230 billion tonnes of lithium, dissolved mainly as lithium salts. While this constitutes the bulk of the lithium on the planet, it’s far too diffuse — a mere 25 micromolar — to serve as a viable commercial source without vast expenditures of energy to extract and concentrate it. But seawater isn’t the only brine that contains lithium, and extracting the valuable metal from underground brines has become the main production method since the 1990s.
By far the biggest lithium-bearing brines are found in the “Lithium Triangle” of South America. Occupying parts of Chile, Bolivia, and Argentina, the area is home to large salt flats or salars, areas where ancient lakes or ponds evaporated, leaving behind salts and other precipitated minerals. These salt flats have built up over millions of years, leaving rich layers of minerals beneath their surfaces. And as we’ll see, the flat terrain and harsh arid conditions on the surface also play a part in the mining process.
Mining lithium brine is quite unlike any of the other methods of mining we’ve covered before, and couldn’t be simpler. Instead of digging up rocks and painstakingly isolating the material of interest, brine mining consists of injecting water down into salt deposits through deep boreholes. The water dissolves the salt deposits, creating a rich brine that can be pumped up to the surface. The brine is pumped into shallow ponds and is left in the sun to evaporate.
When most of the water in a pond has evaporated — up to two years later — the now concentrated brine is harvested. The concentrate contains a variety of elements in addition to lithium, including sodium, magnesium, phosphates, and boron. The concentrate can either be further processed on-site, or as is becoming increasingly common, shipped via pipelines to ports for transport to lithium processing plants abroad.
On the face of it, the evaporation method for lithium brine mining seems like a winner. It’s super simple, it’s powered almost exclusively by the sun, and it’s devoid of some of the impacts that a large open-pit mining operation can have. But there are still huge problems with evaporation concentration. First off, it requires vast amounts of water to create the brines in the first place, and because evaporation ponds are only practical in places where it doesn’t rain much, water is already in short supply. The water used for brine mining is also lost to the atmosphere, coming back to the surface somewhere far from the evaporation ponds. Plus, the evaporation ponds occupy unbelievably large amounts of land — some pond complexes cover an area the size of Manhattan — which makes it difficult to scale up operations. And the amount of time it takes the sun to do its work is a problem in terms of production flexibility.
A Better Way
To make the most of brine mining while mitigating its shortcomings, direct lithium extraction methods are becoming increasingly popular. In DLE, brine is pumped from underground sources, but instead of concentrating the brine by open evaporation, lithium is removed from the brine using a number of chemical and physical methods. One method is ion-exchange adsorption, where the brine is mixed with an absorbent material that preferentially binds lithium compounds over the other compounds in the brine. One class of sorbents used in DLE is known as layered double hydroxides (LDH), materials with a layered structure that allows lithium chloride in the brine to fit between the layers while excluding the potassium, magnesium, and other salts. The brine is returned to the ground, while the high-purity lithium chloride is washed off the sorbent.
Other DLE methods include membrane-separation technologies like reverse osmosis, where the brine is pumped at high pressure through membranes with pores that retain the lithium salts, or by solvent extraction, where organic solvents are used to extract the lithium. The common theme with DLE methods, though, is the fact that they are closed-loop processes — the water used to create the brine is returned to the underground formations containing the lithium. DLE plants also take up a fraction of the physical space that even a single evaporation pond would take, and they don’t rely on extreme environments like salars to work.
Best of Both Worlds
As attractive as DLE technology is, at the scale needed to be commercially viable, DLE plants still require a fair amount of energy to run. But in some places, a quirk of geology has left ample lithium deposits near a source of abundant renewable energy. In the Imperial Valley of California lies the Salton Sea, an inland saline lake that lies atop a series of active geological faults, including the famous San Andreas fault. The area is perfect for geothermal electricity production, with eleven plants currently producing 2,250 MW. Some of these geothermal plants are co-located with DLE plants, which pump up hot, lithium-rich brines that are purified using the geothermal energy produced on-site. Environmentally speaking, such plants are about as low-impact as lithium production can be, with the geothermal DLE plant being built by Australian company Controlled Thermal Resources predicted to produce 68,000 tonnes of battery-grade lithium by 2027.
With the demand for lithium set to soar, the ability to extract what we can from the limited sources we have available using the lowest amount of energy possible is becoming a challenge indeed. Geothermal DLE seems like a good start, but the number of places in the world with both the correct geochemistry and the tectonics to support such operations is limited. It’s going to take some clever engineering to get at the rest of the lithium that’s available, at least with the technology and energy resources we currently have.
[Banner photo by PABLO COZZAGLIO/AFP via Getty Images]
Almost exactly a year ago, we launchedRaspberry Pi Pico, the first product powered by our own microcontroller, RP2040. Since then, we’ve sold nearly 1.5 million Picos, and thousands of you have used RP2040 in your own electronic projects and products.
Since June, RP2040 has been available through our worldwide network of Approved Resellers, for a single-unit price of $1. This remains the best way to get your hands on the chip for prototyping, and for small- to medium-scale production. But as RP2040 products begin to ramp to scale, and the global semiconductor shortage has transmuted most other microcontrollers into unobtainium, we’ve started to see people asking to buy tens of thousands of chips at a time.
Raspberry Pi Direct is an online storefront, which currently sells exactly two products:
Reels of 500 RP2040 chips, with a unit price of $0.80
Reels of 3,400 RP2040 chips, with a unit price of $0.70
Simply create an account, add products to your basket, and check out as you would do in any online store. We’ll contact you to arrange payment by bank transfer (Raspberry Pi Direct does not support credit or debit card payments), and ship your products once funds clear.
Unobtainium no longer
RP2040 is built on a more modern semiconductor process (TSMC 40LP) than most other microcontrollers. As a result, it makes extremely efficient use of scarce silicon wafer supply: each die occupies just 2mm2, and each 300mm wafer yields roughly 21,000 dice. We have sufficient wafer stock on hand to produce 20 million chips, with more on the way.
If you want to build your product on a microcontroller you can actually buy in 2022, RP2040 is your friend. Head on over to Raspberry Pi Direct to get yours today.
[Dries Depoorter] has a knack for highly technical projects with a solid artistic bent to them, and this piece is no exception. The Flemish Scrollers is a software system that watches live streamed sessions of the Flemish government, and uses Python and machine learning to identify and highlight politicians who pull out phones and start scrolling. The results? Pushed out live on Twitter and Instagram, naturally. The project started back in July 2021, and has been dutifully running ever since, so by now we expect that holding one’s phone where the camera can see it is probably considered a rookie mistake.
This project can also be considered a good example of how to properly handle confidence in results depending on the application. In this case, false negatives (a politician is using a phone, but the software doesn’t detect it properly) are much more acceptable than false positives (a member gets incorrectly identified, or is wrongly called-out for using a mobile device when they are not.)
Keras, an open-source software library, is used for the object detection and facial recognition (GitHub repository for Keras is here.) We’ve seen it used in everything from bat detection to automatic trash sorting, so if you’re interested in machine learning applications, give it a peek.
The original Game Boy was the greatest selling handheld video game system of all time, only to be surpassed by one of its successors. It still retains the #2 position by a wide margin, but even so, they’re getting along in years now and finding one in perfect working condition might be harder than you think. What’s more likely is you find one that’s missing components, has a malfunctioning screen, or has had its electronics corroded by the battery acid from a decades-old set of AAs.
That latter situation is where [Taylor] found himself and decided on performing a full restoration on this classic. To get started, he removed all of the components from the damaged area so he could see the paths of the traces. After doing some cleaning of the damage and removing the solder mask, he used 30 gauge wire to bridge the damaged parts of the PCB before repopulating all of the parts back to their rightful locations. A few needed to be replaced, but in the end the Game Boy was restored to its former 90s glory.
This build is an excellent example of what can be done with a finely tipped soldering iron while also being a reminder not to leave AA batteries in any devices for extended periods of time. The AA battery was always a weak point for the original Game Boys, so if you decide you want to get rid of batteries of any kind you can build one that does just that.