By Danny Freedman
With the dawn of the Iron Age more than 3,000 years ago, the ability to produce and use iron metal shifted the course of civilization. Now scientists at GW are hoping to create another shift by changing the way iron is made, using a new process that leaves behind no carbon dioxide emissions.
“We’ve been making iron the same way for millennia and it’s just been pumping carbon dioxide into the atmosphere and it’s a huge contributor to greenhouse gases,” says GW chemistry professor Stuart Licht. “This looks like a good alternative. It’s terribly exciting.”
Dr. Licht and co-author Baohui Wang, who worked on the research as a visiting scholar from Northeast Petroleum University, in China, report that they found a new path to producing iron by first being able to dissolve the two most commonly used types of iron ore—mined rocks that contain iron—in a molten carbon solution, a process previously “thought to be impossible,” says Dr. Licht.
This allowed the researchers to generate iron through a process called electrolysis, which can be powered by renewable energy—including a new solar technique they recently developed—which results in no carbon dioxide emissions.
Even if the electrolysis were driven by fossil fuels, the researchers said it would generate less than half the carbon dioxide of current industrial iron production.
The study was published online today in the journal Chemical Communications.
Currently, according to the study, iron is produced industrially via smelting, a process that uses hot air and a coal residue, called “coke,” to melt iron ore and separate and collect the pure iron.
Production of iron and steel (which is an iron-carbon mixture) accounts for a quarter of the world’s industrial carbon dioxide emissions, according to the researchers.
Instead, Dr. Licht and Dr. Wang found that they were able to dissolve the iron ores in a molten solution of lithium carbonate, heated to 800 degrees Celsius (1,472 degrees Fahrenheit) and above. At such high temperatures, it also becomes easier to split the molecules through electrolysis.
For that, an electrical current is added to the molten mix and the dissolved iron ore is separated into its component parts, iron and oxygen, and collected by two electrodes in the solution.
The iron, which gathered in a clump with trapped salts, was then ground into a powder and cleaned, resulting in iron metal as we know it: “reflective, grey and metallic,” the researchers write, as well as magnetic.
In a link to their recent work, Dr. Licht and Dr. Wang showed this electrolysis process can be fueled by not only conventional power but also a new solar-powered technique they reported this summer, called the solar thermal electrochemical photo (or STEP) process.
(Developed with other GW researchers and a collaborator from Howard University, that research appears in the Aug. 5 edition of the Journal of Physical Chemistry Letters.)
Their STEP process generates the high temperatures they need by using the sun’s thermal energy, which Dr. Licht says is usually damaging to solar cells and discarded. In STEP, it’s deflected onto the lithium carbonate to melt it. Meanwhile, the sun’s visible light is used to generate the electric charge that divides the iron molecules.
In the previous study the scientists demonstrated how the process could be used to break down carbon dioxide into oxygen and (depending on the temperature) either carbon monoxide gas or solid carbon—the latter being “kind of elegant in terms of poetic justice,” says Dr. Licht. “We’re converting carbon dioxide back to coal, if you will.”
Reformulating carbon dioxide into solid carbon creates a storable form of energy, but even the generation of carbon monoxide is beneficial. “It’s a wonderful starting point,” he says, since it can be combined with hydrogen (made the same way, by splitting water into hydrogen and oxygen), to create synthetic diesel and jet fuel.
Dr. Licht says he also is working on using the STEP process to create bleach.
Capturing carbon dioxide and turning it into its useful constituent parts “has been one of the tremendous challenges that we’ve had as scientists,” says Dr. Licht, “and we’ve overcome that.”
Prior attempts at doing this with sunlight, he says, have reached efficiencies of only 1 percent or 2 percent, in terms of turning solar energy into electrical energy; with STEP “we’re talking 34 percent to over 50 percent,” he says. “So it’s a change of mindset.”
His hope is that their STEP research demonstrates that industrial processes can be fueled by renewable resources, like solar power. “I would like us to consider, rather than a fossil fuel economy, a renewable chemical economy,” he says. “We have become addicted to electricity through the grid.”