First detection of light from behind a black hole

Peer-Reviewed Publication

STANFORD UNIVERSITY

 

IMAGE: RESEARCHERS OBSERVED BRIGHT FLARES OF X-RAY EMISSIONS, PRODUCED AS GAS FALLS INTO A SUPERMASSIVE BLACK HOLE. THE FLARES ECHOED OFF OF THE GAS FALLING INTO THE BLACK HOLE, AND AS THE FLARES WERE SUBSIDING, SHORT FLASHES OF X-RAYS WERE SEEN – CORRESPONDING TO THE REFLECTION OF THE FLARES FROM THE FAR SIDE OF THE DISK, BENT AROUND THE BLACK HOLE BY ITS STRONG GRAVITATIONAL FIELD. view more 

CREDIT: DAN WILKINS

Watching X-rays flung out into the universe by the supermassive black hole at the center of a galaxy 800 million light-years away, Stanford University astrophysicist Dan Wilkins noticed an intriguing pattern. He observed a series of bright flares of X-rays – exciting, but not unprecedented – and then, the telescopes recorded something unexpected: additional flashes of X-rays that were smaller, later and of different “colors” than the bright flares.

According to theory, these luminous echoes were consistent with X-rays reflected from behind the black hole – but even a basic understanding of black holes tells us that is a strange place for light to come from.

“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” said Wilkins, who is a research scientist at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford and SLAC National Accelerator Laboratory. It is another strange characteristic of the black hole, however, that makes this observation possible. “The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself,” Wilkins explained.

The strange discovery, detailed in a paper published July 28 in Nature, is the first direct observation of light from behind a black hole – a scenario that was predicted by Einstein’s theory of general relativity but never confirmed, until now.

“Fifty years ago, when astrophysicists starting speculating about how the magnetic field might behave close to a black hole, they had no idea that one day we might have the techniques to observe this directly and see Einstein’s general theory of relativity in action,” said Roger Blandford, a co-author of the paper who is the Luke Blossom Professor in the School of Humanities and Sciences, Stanford professor of physics and SLAC professor of particle physics and astrophysics.

How to see a black hole

The original motivation behind this research was to learn more about a mysterious feature of certain black holes, called a corona. Material falling into a supermassive black hole powers the brightest continuous sources of light in the universe, and as it does so, forms a corona around the black hole. This light – which is X-ray light – can be analyzed to map and characterize a black hole.

The leading theory for what a corona is starts with gas sliding into the black hole where it superheats to millions of degrees. At that temperature, electrons separate from atoms, creating a magnetized plasma. Caught up in the powerful spin of the black hole, the magnetic field arcs so high above the black hole, and twirls about itself so much, that it eventually breaks altogether – a situation so reminiscent of what happens around our own Sun that it borrowed the name “corona.”

“This magnetic field getting tied up and then snapping close to the black hole heats everything around it and produces these high energy electrons that then go on to produce the X-rays,” said Wilkins.

As Wilkins took a closer look to investigate the origin of the flares, he saw a series of smaller flashes. These, the researchers determined, are the same X-ray flares but reflected from the back of the disk – a first glimpse at the far side of a black hole.

“I’ve been building theoretical predictions of how these echoes appear to us for a few years,” said Wilkins. “I’d already seen them in the theory I’ve been developing, so once I saw them in the telescope observations, I could figure out the connection.”

Future observations

The mission to characterize and understand coronas continues and will require more observation. Part of that future will be the European Space Agency’s X-ray observatory, Athena (Advanced Telescope for High-ENergy Astrophysics). As a member of the lab of Steve Allen, professor of physics at Stanford and of particle physics and astrophysics at SLAC, Wilkins is helping to develop part of the Wide Field Imager detector for Athena.

“It’s got a much bigger mirror than we’ve ever had on an X-ray telescope and it’s going to let us get higher resolution looks in much shorter observation times,” said Wilkins. “So, the picture we are starting to get from the data at the moment is going to become much clearer with these new observatories.”

Co-authors of this research are from Saint Mary’s University (Canada), Netherlands Institute for Space Research (SRON), University of Amsterdam and The Pennsylvania State University.

This work was supported by the NASA NuSTAR and XMM-Newton Guest Observer programs, a Kavli Fellowship at Stanford University, and the V.M. Willaman Endowment at the Pennsylvania State University.

ESA illustration (IMAGE)

STANFORD UNIVERSITY

CAPTION

Illustration of how light echoes from behind a black hole.

CREDIT

ESA

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JOURNAL

Nature

DOI

10.1038/s41586-021-03667-0

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE PUBLICATION DATE

28-Jul-2021

 

Computer science, environmental health experts at UIC team up to protect US Navy divers with AI

Office of Naval Research awards UIC, DPI researchers $725,000

Grant and Award Announcement

UNIVERSITY OF ILLINOIS AT CHICAGO

 

IMAGE: RESEARCHERS AT UIC ARE WORKING ON AN AI SYSTEM TO HELP SAILORS, THANKS TO A TWO-YEAR, $725,000 GRANT AWARD view more 

CREDIT: VLAD TCHOMPALOV/UNSPLASH

The U.S. Office of Naval Research has awarded University of Illinois Chicago researchers $725,000 to develop an artificial intelligence system that can help protect divers from waterborne bacteria, parasites, and other harmful pathogens and microbes.

Sailors are sent into all kinds of water as part of their service in the U.S. Navy, but they have limited resources to understand in real-time the health risks that may exist when they conduct underwater duties — everything from fleet maintenance and repairs to search and rescue and research missions. The most reliable water testing technologies typically rely on lab-based analysis of samples and scientists knowing which microbes to screen. But with dynamic weather, currents, water temperatures, and sewage and pollution factors, the exact condition of water, particularly of coastal water, at a specific time is hard to predict.

“By the time a water sample arrives at a lab and is tested, the conditions may have changed,” said Dr. Samuel Dorevitch, associate professor of environmental and occupational health sciences at the School of Public Health and co-principal investigator. “If Navy divers had real-time information, they could select the best protective equipment, dive duration and take other measures to prevent the various health issues, like heat stress or gastrointestinal, skin, and respiratory infections that may result from microbes in water.”

That’s where a new approach using artificial intelligence can make a difference.

“Artificial intelligence offers a way to synthesize a vast amount of information quickly for a specific calculation and this technology, if we can bring it to fruition, provides an opportunity for us to improve the tools available to the Navy,” said Isabel Cruz, distinguished professor of computer science at the College of Engineering and co-principal investigator.

The researchers hope that they can develop a system that can be used in any location by divers to analyze water conditions through a combination of user-provided and web-based information and human data, such as the age of the divers, their health, and the size of the diving team.

“This project is both exciting and challenging because of its multidimensionality,” Cruz said. “We hope to pull information from many sources that offer different types of data, and we will have to integrate data that are quite complex, heterogeneous, and often without metadata. We will build the artificial intelligence and machine learning methods in stages, and if we can teach our system to reliably and accurately filter and prioritize all these data for risk prediction, I think we will have something remarkable.”

“If we could provide divers or their commanders with a handheld device or app to evaluate the ever-changing ecosystem of a particular body of water and any potential health risks at the time they enter the water, they would be better able to plan their mission for optimal health and safety,” Dorevitch said. “For those in the Navy, getting in the water is not optional and anything we can do to aid quick, data-driven decision-making for mitigating health risk is beneficial.”

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Charlie Catlett, senior research scientist at Discovery Partners Institute, is a co-investigator. The grant, which started May 16, will support this research for two years.

 

Scientists capture most-detailed radio image of Andromeda galaxy to date

Disk of galaxy identified as region where new stars are born

Peer-Reviewed Publication

UNIVERSITY OF BRITISH COLUMBIA

 

IMAGE: RADIO IMAGE OF ANDROMEDA GALAXY AT 6.6 GHZ (INSET), CAPTURED USING THE SARDINIA RADIO TELESCOPE IN ITALY. view more 

CREDIT: S. FATIGONI ET AL (2021)

Scientists have published a new, detailed radio image of the Andromeda galaxy – the Milky Way’s sister galaxy – which will allow them to identify and study the regions of Andromeda where new stars are born.

The study – which is the first to create a radio image of Andromeda at the microwave frequency of 6.6 GHz – was led by University of British Columbia physicist Sofia Fatigoni, with colleagues at Sapienza University of Rome and the Italian National Institute of Astrophysics. It was published online in Astronomy and Astrophysics.

“This image will allow us to study the structure of Andromeda and its content in more detail than has ever been possible,” said Fatigoni, a PhD student in the department of physics and astronomy at UBC. “Understanding the nature of physical processes that take place inside Andromeda allows us to understand what happens in our own galaxy more clearly – as if we were looking at ourselves from the outside.”

Prior to this study, no maps capturing such a large region of the sky around the Andromeda Galaxy had ever been made in the microwave band frequencies between one GHz to 22 GHz. In this range, the galaxy’s emission is very faint, making it hard to see its structure. However, it is only in this frequency range that particular features are visible, so having a map at this particular frequency is crucial to understanding which physical processes are happening inside Andromeda.

In order to observe Andromeda at this frequency, the researchers required a single-dish radio telescope with a large effective area. For the study, the scientists turned to the Sardinia Radio Telescope, a 64-metre fully steerable telescope capable of operating at high radio frequencies.

It took 66 hours of observation with the Sardinia Radio Telescope and consistent data analysis for the researchers to map the galaxy with high sensitivity. They were then able to estimate the rate of star formation within Andromeda, and produce a detailed map that highlighted the disk of the galaxy as the region where new stars are born.

“By combining this new image with those previously acquired, we have made significant steps forward in clarifying the nature of Andromeda’s microwave emissions and allowing us to distinguish physical processes that occur in different regions of the galaxy,” said Dr. Elia Battistelli, a professor in the department of physics at Sapienza and coordinator of the study.

“In particular, we were able to determine the fraction of emissions due to thermal processes related to the early stations of new star formation, and the fraction of radio signals attributable to non-thermal mechanisms due to cosmic rays that spiral in the magnetic field present in the interstellar medium,” Fatigoni said.

For the study, the team developed and implemented software that allowed – among other things – to test new algorithms to identify never-before-examined lower emission sources in the field of view around Andromeda at a frequency of 6.6 GHz. From the resulting map, researchers were able to identify a catalog of about 100 point sources, including stars, galaxies and other objects in the background of Andromeda.

CAPTION

The Sardinia Radio Telescope located in Sardinia, Italy.

CREDIT

S. Fatigoni et al (2021)

USAGE RESTRICTIONS

Include credit information

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JOURNAL

Astronomy and Astrophysics

DOI

10.1051/0004-6361/202040011

ARTICLE TITLE

Study of the thermal and nonthermal emission components in M31: the Sardinia Radio Telescope view at 6.6 GHz

ARTICLE PUBLICATION DATE

23-Jul-2021

COI STATEMENT

None

CAPTION

Lead author Sofia Fatigoni

CREDIT

Sofia Fatigoni

 

Water as a metal

Peer-Reviewed Publication

HELMHOLTZ-ZENTRUM BERLIN FÜR MATERIALIEN UND ENERGIE

 

IMAGE: IN THE SAMPLE CHAMBER, THE NAK ALLOY DRIPS FROM A NOZZLE. AS THE DROPLET GROWS, WATER VAPOUR FLOWS INTO THE SAMPLE CHAMBER AND FORMS A THIN SKIN ON THE DROP'S SURFACE. view more 

CREDIT: HZB

Every child knows that water conducts electricity - but this refers to "normal" everyday water that contains salts. Pure, distilled water, on the other hand, is an almost perfect insulator. It consists of H2O molecules that are loosely linked to one another via hydrogen bonds. The valence electrons remain bound and are not mobile. To create a conduction band with freely moving electrons, water would have to be pressurised to such an extent that the orbitals of the outer electrons overlap. However, a calculation shows that this pressure is only present in the core of large planets such as Jupiter.

Providing electrons

An international collaboration of 15 scientists from eleven research institutions has now used a completely different approach to produce a aqueous solution with metallic properties for the first time and documented this phase transition at BESSY II. To do this, they experimented with alkali metals, which release their outer electron very easily.

Avoiding explosion

However, the chemistry between alkali metals and water is known to be explosive. Sodium or other alkali metals immediately start to burn in water. But the team found a way to keep this violent chemistry in check: They did not throw a piece of alkali metal into water, but they did it the other way round: they put a tiny bit of water on a drop of alkali metal, a sodium-potassium (Na-K) alloy, which is liquid at room temperature.

Experiment at BESSY II

At BESSY II, they set up the experiment in the SOL³PES high vacuum sample chamber at the U49/2 beamline. The sample chamber contains a fine nozzle from which the liquid Na-K alloy drips. The silver droplet grows for about 10 seconds until it detaches from the nozzle. As the droplet grows, some water vapour flows into the sample chamber and forms an extremely thin skin on the surface of the droplet, only a few layers of water molecules. This almost immediately causes the electrons as well as the metal cations to dissolve from the alkali alloy into the water. The released electrons in the water behave like free electrons in a conduction band.

Golden water skin

"You can see the phase transition to metallic water with the naked eye! The silvery sodium-potassium droplet covers itself with a golden glow, which is very impressive," reports Dr. Robert Seidel, who supervised the experiments at BESSY II. The thin layer of gold-coloured metallic water remains visible for a few seconds. This enabled the team led by Prof. Pavel Jungwirth, Czech Academy of Sciences, Prague, to prove with spectroscopic analyses at BESSY II and at the IOCB in Prague that it is indeed water in a metallic state.

Fingerprints of the metallic phase

The two decisive fingerprints of a metallic phase are the plasmon frequency and the conduction band. The groups were able to determine these two quantities using optical reflection spectroscopy and synchrotron X-ray photoelectron spectroscopy: While the plasmon frequency of the gold-coloured, metallic "water skin" is about 2.7 eV (i.e. in the blue range of visible light), the conduction band has a width of about 1.1 eV with a sharp Fermi edge. "Our study not only shows that metallic water can indeed be produced on Earth, but also characterises the spectroscopic properties associated with its beautiful golden metallic luster," says Seidel.

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JOURNAL

Nature

DOI

10.1038/s41586-021-03646-5

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Spectroscopic Evidence for a Gold-Coloured Metallic Water Solution

ARTICLE PUBLICATION DATE

27-Jul-2021

COI STATEMENT

none

Metallic water prepared for first time under terrestrial conditions

Peer-Reviewed Publication

INSTITUTE OF ORGANIC CHEMISTRY AND BIOCHEMISTRY OF THE CZECH ACADEMY OF SCIENCES (IOCB PRAGUE)

 

IMAGE: THE FIRST IMAGE SHOWS A PURE DROP OF SODIUM-POTASSIUM ALLOY; IN THE NEXT IMAGES, WE SEE THE DROP EXPOSED TO THE ACTION OF THE WATER VAPOR AT 10-4 MBAR. A LAYER OF WATER FORMS ON THE DROP, IN WHICH ELECTRONS LIBERATED FROM THE METAL DISSOLVE, GIVING IT A GOLDEN METALLIC SHEEN. view more 

CREDIT: PHOTO: PHIL MASON / IOCB PRAGUE

Pure water is not a good conductor of electricity. It is, in fact, an electrical insulator. In order to conduct electricity, water must contain dissolved salts, for example, yet the conductivity of such an electrolyte is relatively low, several orders lower than that of metals. Is it possible to produce water that is as conductive as, say, copper wire? Scientists have hypothesized that this may take place in the cores of large planets, where high pressure compresses water molecules to the point that their electron shells begin to overlap. At present, generating that kind of pressure on Earth exceeds human capabilities, and it was therefore assumed that preparing metallic water under terrestrial conditions would remain an elusive goal for the foreseeable future. However, an international team of researchers headed by Pavel Jungwirth of IOCB Prague has developed a new method with which they succeeded in making metallic water under terrestrial conditions that lasted for several seconds. Their paper was recently published in Nature.

The idea of using immense pressure to make metal out of water is nothing new. In principle, it should be possible to compress water molecules to the point that their electron shells begin to overlap and form a so-called conduction band similar to the one in metallic materials. The required pressure of 50 Mbar (i.e. approximately 50 million times greater than on the surface of Earth) can be found in the cores of large planets, but we are not yet able to achieve it under terrestrial conditions.

In collaboration with researchers from the University of Southern California, the Fritz Haber Institute, and other institutes, Jungwirth’s team recently developed a method that has allowed them to prepare metallic water while completely sidestepping the need for high pressure. The method builds on earlier research of the Pavel Jungwirth Group focusing on the behavior of alkali metals in water and liquid ammonia. Inspired by work with alkali metal-liquid ammonia solutions, which at high concentrations behave like a metal, the researchers decided to attempt creation of a conduction band not by compressing water molecules but rather by way of massive dissolution of the electrons released from the alkali metal. In doing so, however, they had to overcome a fundamental obstacle: on introduction to water, alkali metals immediately explode.

“Throwing sodium into water is one of the most popular school experiments and the subject of many a YouTube video. As is well known, when you throw a chunk of sodium in water, you don’t get metallic water but an immediate and substantial explosion that takes out your apparatus,” says Jungwirth, who heads a group at IOCB Prague specializing in molecular modeling. “In order to contain this intense and, for laboratory purposes, rather counterproductive chemistry, we approached it the other way around; instead of adding the alkali metal to the water, we added the water to the metal.”

Inside a vacuum chamber, the researchers exposed a drop of sodium-potassium alloy to a small amount of water vapor, which began to condense on its surface. The electrons liberated from the alkali metal dissolved in the layer of water on the surface faster than the chemical reaction that results in the explosion. There were a sufficient number of them to overcome the critical limit for the formation of a conduction band and thus give rise to a metallic water solution, which in addition to the electrons also contained dissolved alkali cations and chemically formed hydroxide and hydrogen.

“Thanks to this, we were able to create a thin layer of gold-colored metallic water solution that lasted for several seconds, and that was enough for us to not only see it with our own eyes but also measure it with spectrometers,” says Jungwirth, adding: “We more or less jury-rigged the necessary apparatus in a small lab at our institute in Prague, which is also where the fist experiments took place. We then obtained the key evidence for the presence of metallic water using X-ray photoelectron spectroscopy on the synchrotron in Berlin.”

Artistic rendering of a pure sodium-potassium alloy drop and a drop with a layer of water, in which electrons liberated from the metal dissolved (IMAGE)

INSTITUTE OF ORGANIC CHEMISTRY AND BIOCHEMISTRY OF THE CZECH ACADEMY OF SCIENCES (IOCB PRAGUE)

CAPTION

On the left is a pure drop of sodium-potassium alloy, on the right is the drop with a layer of water, in which electrons liberated from the metal dissolved, giving it a golden metallic sheen.

CREDIT

Artistic rendering: Tomáš Belloň / IOCB Prague

The study of the researchers at IOCB Prague and their colleagues, now published in Nature, not only shows that metallic water can be prepared under terrestrial conditions, but it also provides a detailed characterization of the spectroscopic properties connected to its beautiful golden metallic sheen.

The original article:

Philip E. Mason, H. Christian Schewe, Tillmann Buttersack, Vojtech Kostal, Marco Vitek, Ryan S. McMullen, Hebatallah Ali, Florian Trinter, Chin Lee, Daniel M. Neumark, Stephan Thürmer, Robert Seidel, Bernd Winter, Stephen E. Bradforth, and Pavel Jungwirth. Spectroscopic evidence for a gold-coloured metallic water solution. Nature 2021. DOI: 10.1038/s41586-021-03646-5

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JOURNAL

Nature

DOI

10.1038/s41586-021-03646-5

METHOD OF RESEARCH

Experimental study

ARTICLE TITLE

Spectroscopic evidence for a gold-coloured metallic water solution

ARTICLE PUBLICATION DATE

27-Jul-2021

Disclaimer: AAAS and Eu

 

More WHITE American parents of teens are purchasing firearms during the pandemic, study finds

One in seven of the households that purchased a gun also had a teen with depression.

Peer-Reviewed Publication

MICHIGAN MEDICINE - UNIVERSITY OF MICHIGAN

Since the start of the COVID-19 pandemic, more parents of teenagers in the United States started buying firearms, according to a recent study.

In a national survey of primary caretakers of teenagers conducted by the Firearm Safety Among Children and Teens, or FACTS, Consortium, 10% of all households with high school-age teens reported buying a firearm in the early months of the pandemic between March and July of 2020, and 3% of U.S. households with teens became first-time gun owners. 

While firearm manufacturing and sales have grown steadily since the 1990s, researchers estimate that in the first few months of the coronavirus pandemic 2.1 million additional firearm purchases were made nationwide – a 64.3% increase over expected volume.

For households that already owned a firearm, these new firearms were more likely to be acquired by those who already reported storing at least one gun unlocked and loaded, noted the study, published in the Journal of Behavioral Medicine.

“This finding is concerning because we know that the single biggest risk factor for adolescent firearm injuries is access to an unsecured firearm,” said Patrick Carter, M.D., a co-author of the paper and co-director of the new Institute for Firearm Injury Prevention at the University of Michigan. “This study demonstrates that we have more work to do to help families that already have firearms, or may purchase new firearms, to reduce the potential risks to their children by promoting safer storage practices that help to reduce the risk of teen firearm injury and death.”

Each year, nearly 50 out of every 100,000 high school-age teens are injured by firearms and 10 out of every 100,000 are killed. As a result, teens in that age group are more likely to die from a firearm injury than any other leading cause of death.

While the mental health statuses of parents and teens weren’t associated with the likelihood of purchasing a firearm, researchers found that one in seven households, 14%, that purchased a gun during the beginning of the COVID pandemic also had a teen who was experiencing depression symptoms.

These findings, taken together, have significant implications for public health practitioners faced with both the COVID-19 pandemic and the firearm injury epidemic, said Marc Zimmerman, Ph.D., a co-author on the publication and co-director of the new U-M Firearm Injury Prevention Institute alongside Carter.

“If we know that families are storing firearms unsafely and that a certain amount of them have teens who are experiencing depression, that can inform how we would tailor messaging around safe storage to families at increased risk,” Zimmerman said.

The Institute for Firearm Injury Prevention The Institute for Firearm Injury Prevention launched in June crises of firearm injury, from which 100 people die each day in the United States. The institute is supported by a $10 million university commitment, with U-M researchers already having secured more federal funding to study the issue than any other academic institute in the nation.

In this study, the research team concluded that strategies geared towards safe storage for parents, as well as stronger child access prevention policy initiatives, could reduce the risk of firearm injury among teens.

“It’s unclear exactly what specific circumstances precipitated this change in firearm purchasing, but we know that future research needs to focus on ways to increase safe storage practices among families with teens,” Zimmerman said. “The implications of this line of research may extend beyond the current COVID-19 pandemic and could help us move forward our goal of reducing and preventing future firearm injuries.”

Paper cited: “Firearm purchasing during the beginning of the COVID-19 pandemic in households with teens: a national study,” Journal of Behavioral Medicine. DOI: 10.1007/s10865-021-00242-w

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JOURNAL

Journal of Behavioral Medicine

DOI

10.1007/s10865-021-00242-w

METHOD OF RESEARCH

Survey

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Firearm purchasing during the beginning of the COVID-19 pandemic in households with teens: a national study

ARTICLE PUBLICATION DATE

9-Jul-2021

COI STATEMENT

The authors have no conflicts of interest to disclose.

 

Scientists synthesize a material which can completely replace natural gypsum in the construction industry

Peer-Reviewed Publication

NATIONAL UNIVERSITY OF SCIENCE AND TECHNOLOGY MISIS

 

IMAGE: NATURAL GYPSUM STONE view more 

CREDIT: AUTHOR: MAKSIM SAFANIUK

An international team of scientists has proposed a method of production of high-quality gypsum binders based on synthetic calcium sulfate dihydrate produced from industrial waste. Tests of the obtained material have shown that it not only meets all the requirements for materials of this class, but also surpasses binders based on natural gypsum in several parameters. The work has been published in the Journal of Industrial and Engineering Chemistry. 
Gypsum binders are widely used in construction. They have valuable properties such as low weight, low heat and sound conductivity, fire resistance, and they are easy to shape. In addition, gypsum-based binders are hypoallergenic and do not cause silicosis, an occupational disease for builders and repairmen caused by inhalation of dust containing free silicon dioxide. At the same time, the cost of gypsum materials is low, as are the costs of heat energy for their production.
A group of scientists from NUST MISIS, Belarusian State Technological University, University of Limerick and the Institute of General and Inorganic Chemistry of the National Academy of Sciences of Belarus has proposed an innovative method of producing high-strength binders based on synthetic gypsum obtained from industrial waste by neutralizing spent sulfuric acid and carbonate components. Researchers mixed sulfuric acid from waste heat-resistant fibers with water and limestone. The content of calcium sulfate dihydrate in the obtained synthetic gypsum was at least 95% of the mass of the final product.
In the course of the study, scientists obtained three types of synthetic gypsum samples: building gypsum, high-strength gypsum and anhydrite. The building gypsum was made using traditional technology in a gypsum boiler. Anhydrite was also produced according to the traditional technology for this type of gypsum material by firing followed by cooling. An autoclave was used to synthesize high-strength gypsum.
The researchers point out that one of the advantages of producing building gypsum materials from synthetic calcium sulfate dihydrate is that the synthetic gypsum is obtained immediately in the form of a powder product. In the traditional production of gypsum powder, gypsum has to be crushed to the desired state, which requires a significant amount of electricity. Thus, the method proposed by scientists for the production of binders based on synthetic gypsum will significantly reduce production costs by simplifying the production technology. At the same time, the building gypsum obtained in the course of the study fully meets the requirements for gypsum binders of the G5 - G7 grades, for high-strength gypsum - the requirements for gypsum grades G10 - G22.
Synthetic gypsum, obtained from waste sulfuric acid and limestone waste, can completely replace natural gypsum for the production of gypsum binders in countries that do not have gypsum stone deposits.
 

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JOURNAL

Journal of Industrial and Engineering Chemistry

DOI

https://doi.org/10.1016/j.jiec.2021.05.006

ARTICLE TITLE

High-quality gypsum binders based on synthetic calcium sulfate dihydrate produced from industrial waste