New method for making tiny catalysts holds promise for air quality

Dec 15, 2010
Civil and environmental engineering professor Mark Rood (left) and graduate student John Atkinson developed a novel method of producing porous carbon spheres with iron dispersed throughout them for catalytic and air quality applications. Credit: L. Brian Stauffer

Fortified with iron: It's not just for breakfast cereal anymore. University of Illinois researchers have demonstrated a simpler method of adding iron to tiny carbon spheres to create catalytic materials that have the potential to remove contaminants from gas or liquid.

Civil and environmental engineering professor Mark Rood, graduate student John Atkinson and their team described their technique in the journal .

Carbon structures can be a support base for catalysts, such as iron and other metals. Iron is a readily available, low-cost with possible catalytic applications for fuel cells and environmental applications for adsorbing harmful chemicals, such as arsenic or carbon monoxide. Researchers produce a carbon matrix that has many or tunnels, like a sponge. The large surface area created by the pores provides sites to disperse tiny iron particles throughout the matrix.

A common source of carbon is coal. Typically, scientists modify coal-based materials into highly porous activated carbon and then add a catalyst. The multi-step process takes time and enormous amounts of energy. In addition, materials made with coal are plagued by ash, which can contain traces of other metals that interfere with the reactivity of the carbon-based catalyst.

The Illinois team's ash-free, inexpensive process takes its carbon from sugar rather than coal.

In one continuous process, it produces tiny, micrometer-sized spheres of porous, spongy carbon embedded with iron – all in the span of a few seconds.

"That's what really sets this apart from other techniques. Some people have carbonized and impregnated with iron, but they have no surface area. Other people have surface area but weren't able to load it with iron," Atkinson said. "Our technique provides both the carbon surface and the iron nanoparticles."

The researchers built upon a technique called ultrasonic spray pyrolysis (USP), developed in U. of I. chemistry professor Kenneth Suslick's lab in 2005. Suslick used a household humidifier to make fine mist from a carbon-rich solution, then directed the mist through an extremely hot furnace, which evaporated the water from each droplet and left tiny, highly porous carbon spheres.

Atkinson used USP to make his carbon spheres, but added an iron-containing salt to a carbon-rich sugar solution. When the mist is piped into the furnace, the heat stimulates a reaction between the solution ingredients that creates carbon spheres with iron particles dispersed throughout.

"We were able to take advantage of Dr. Suslick's USP technique, and we are building upon it by simultaneously impregnating the porous carbons with metal nanoparticles," Atkinson said. "It's simple because it's continuous. We can isolate the carbon, add pores, and impregnate iron into the carbon spheres in a single step."

Another advantage of the USP technique is the ability to create materials to address particular needs. By fabricating the material from scratch, rather than trying to modify off-the-shelf products, scientists and engineers can develop materials for specific problem-solving scenarios.

"Right now, you take coal out of the ground and modify it. It's difficult to tailor it to solve a particular air quality problem," Rood said. "We can readily change this new material by how it's activated to tailor its surface area and the amount of impregnated iron. This method is simple, flexible and tailorable."

Next, the researchers will explore applications for the material. Rood and Atkinson have received two grants from the National Science Foundation to develop the carbon-iron spheres to remove nitric oxide, mercury, and dioxin from gas streams – bioaccumulating pollutants that have caused concern as emissions from combustion sources.

Currently, the three pollutants can be dealt with separately by carbon-based adsorbents and catalysts, but the Illinois team and collaborators in Taiwan hope to harness carbon's adsorption properties and iron's reactivity to remove all three pollutants from gas streams simultaneously.

"We're looking at taking advantage of their porosity and, ideally, their catalytic applications as well," Atkinson said. "Carbon is a very versatile material. What's in my mind is a multi-pollutant control where you can use the porosity and the catalyst to tackle two problems at once."

Explore further: Physicists heat freestanding graphene to control curvature of ripples

More information: The paper, "Synthesis and Characterization of Iron-impregnated Porous Carbon Spheres Prepared by Ultrasonic Spray Pyrolysis," is published in the journal Carbon.

Related Stories

A new process for making much-sought iron nanospheres

Feb 19, 2007

Using a process that creates bubbles as hot as the surface of the sun, chemists are reporting development of a new method for making hollow hematite (iron oxide) nanospheres. The University of Illinois at Urbana-Champaign's ...

Ocean iron and CO2 interaction studied

Apr 26, 2007

A French study suggested that iron supply changes from deep water to the ocean's surface might have a greater effect on atmospheric CO2 than thought.

The effects of hydrogen on growing carbon nanotubes

Oct 05, 2010

Carbon nanotubes -- long, hollow cylinders of carbon billionths of a meter in diameter -- have many potential uses in nanotechnology, optics, electronics, and many other fields. The exact properties of nanotubes depend on ...

Recommended for you

Twisted graphene chills out

Sep 17, 2014

(Phys.org) —When two sheets of graphene are stacked in a special way, it is possible to cool down the graphene with a laser instead of heating it up, University of Manchester researchers have shown.

Researchers use liquid inks to create better solar cells

Sep 17, 2014

(Phys.org) —The basic function of solar cells is to harvest sunlight and turn it into electricity. Thus, it is critically important that the film that collects the light on the surface of the cell is designed ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

mjesfahani
not rated yet Dec 16, 2010
I wish you make this method work in Tehran, because air is very polluted.
Modernmystic
not rated yet Dec 16, 2010
Air has been crystal clear where I live for at least the last 37 years...

In fact it's been clear even when I've lived in the "big city".
Jimee
not rated yet Dec 16, 2010
Here in the west we are not so lucky. Lots of times the air looks clear, but the vistas visible when I was a child 50 years ago are obscured all the time now. Long live alternative energy.