In the Lab
New Batteries: Cheaper and Greener?
Israeli researchers have developed a light, non-toxic and cheap rechargeable battery made from magnesium, a technology that might eventually replace lead-acid and nickel-cadmium packs for powering vehicles and storing electricity.
Unlike small but costly lithium batteries and heavy and environmentally hazardous lead and cadmium batteries, magnesium is safe and is very abundant in the Earth's crust, making it ideal for use in batteries.
Since the 1980s, researchers have been trying to make batteries from this ideal metal, but Doron Aurbach and colleagues from BarIlan University in Ramat-Gan are the first to make a practical prototype. Generating 0.9 volts to 1.2 volts -- about the same as a nickel-cadmium battery -- the magnesium prototype can be discharged and recharged many times without losing much power capacity.
In a battery, ions shuttle between two electrodes, the anode and cathode, through a substance called an electrolyte. When the battery is providing power, the ions travel from the anode to the cathode. When it's being recharged, the ions go the other way.
While the first lithium batteries used pure lithium metal as the anode, Aurbach and colleagues discovered that magnesium metal is too brittle to fashion into the thin sheets needed. Instead, the researchers used an alloy of magnesium called AZ-31, which is 3 percent aluminum and 1 percent zinc.
Like lithium batteries that now use materials called intercalators for both electrodes, the magnesium battery needed a material for the cathode that is full of tiny gaps into which magnesium ions could fit. The researchers had previously discovered that magnesium ions could pass in and out of a type of molybdenum sulphide called Mo6S8, a material made from a copper-containing version, but replacing the copper with magnesium. Initial swaps made with electricity were impractical for commercial battery production, but scientists have now perfected a way of ousting the copper using a chemical reaction.
To complete the prototype, Aurbach's team used a gel made from a polymer, an organic liquid, and a chemical that grabs hold of magnesium ions as an electrolyte.
Information from a Nature News Service article was used in this report.
Post Bio-Terrorism Decontamination: New Threats?
University of Texas at Austin Environmental Engineering Professor Richard Corsi has received a $1 million contract from a federal agency to study the physical and chemical interactions that occur between three airborne decontaminants and the surfaces they interact with in buildings.
Corsi's team will initially study three different decontamination agents: chlorine dioxide, ozone and methyl bromide. Chlorine dioxide and ozone are both highly chemically reactive substances used in some water purification systems. Methyl bromide is widely used to exterminate termites. It is chemically stable but may persist in buildings following its application because it soaks into porous materials.
The researchers will determine the behavior of each agent in the presence of 24 materials found extensively indoors, including wallboard, carpet, vinyl and linoleum floor tiles, several wood products, metal, fabrics and paper.
The results of the study will be incorporated into a software package that researchers hope can be used by the U.S. Department of Defense, the U.S. Environmental Protection Agency (EPA), local and state health departments, consultants and others to better respond to bioterrorist attacks.
"They'll be able to plug in figures for how much gypsum board, how much linoleum, how much and what kind of carpeting exists in a room," Corsi said, "and based on that, get numbers for the correct decontaminant to apply, at what concentration and for how long."
At a specially designed laboratory facility on the university's J.J. Pickle Research Campus, the researchers are conducting experiments with disinfectant/material pairs to determine how fast a decontaminant reacts with various material surfaces, and how it changes the reactivity of the materials themselves. They also are trying to determine what building disinfectant byproducts are formed and how long the building disinfectant byproducts remain present as a residue.
Their studies do not deal with the actual killing power of the disinfectants, and no anthrax spores or other bio-toxins are involved. The project is confined to discovering how long a given decontaminant remains active under varying conditions, and what, if any, byproducts remain behind.
"The U.S. Environmental Protection Agency and remediation consultants," Corsi said, "will be able to use our data -- along with knowledge of specific buildings -- to design effective, less costly disinfection systems. Our results will also assist them with re-entry planning."
For more information, visit www.utexas.edu.
Plugging Into the Wind
A University of Missouri-Rolla (UMR) researcher and 11 geological engineering students will use wind power to clean up groundwater at a former munitions site in Nebraska.
The 17,000-acre former Nebraska Ordnance Plant, the site of the project, was used for munitions during World War II and the Korean conflict. Declared a Superfund site in 1990, the soil is contaminated with wastes such as trinitrotoluene (TNT). More than 400 people have wells within three miles of the site, using the water for drinking, livestock and irrigation.
"The preliminary numbers show that it is economically viable to use renewable energy at this site instead of paying the utility cost for electricity, said Curt Elmore, assistant professor of geological engineering at UMR. "We will develop a program to determine how much electricity is generated and the mass of contaminant removed."
Elmore's research group will use a wind turbine to power a groundwater circulation well that removes contaminants from the water. The circulation well extracts water from one interval of an aquifer, treats it, and puts it back in the same aquifer at a different depth, so nothing is wasted, Elmore explained.
The group hopes to conserve the natural resources involved in the project. "Because we are using renewable energy, we won't be contributing to potential pollution of one resource -- the air -- while we clean up another resource -- groundwater. Because we use a renewable resource, we are hoping to achieve total conservation," Elmore said. "It's kind of a holistic approach, that you can remediate the groundwater without doing anything to it except removing the contamination."
As a part of a senior design course, the students will work to identify an appropriate wind turbine system, how best to acquire it, how much to pay a contractor and how to connect it to an existing groundwater remediation system.
In the first phase of the project, the group focused on identifying, procuring, installing and connecting the wind turbine. During the second and final phases the wind turbine will be working and the researchers will measure the amount of electricity consumed by the system, the amount of electricity generated by the wind turbine and the mass of contamination removed. The project should be completed by September 2004.
Elmore said he hopes this program proves attainable to even average homeowners who might have contaminated wells on their property.
The $300,000 project is funded by EPA, the Kansas City District Corps of Engineers, UMR and Bergey Wind Power Co. of Norman, Okla.
This news item originally appeared in the January 2004 issue of Environmental Protection, Vol. 15, No. 1.
This article originally appeared in the 01/01/2004 issue of Environmental Protection.