In the Lab

• By Heida Diefenderfer
• Jan 01, 2002

Fishing for Hydrogel

Srinivasan Damodaran, a University of Wisconsin-Madison food scientist, has patented a biochemical process that could turn carp into a cash crop and, at the same time, reduce the swelling of landfills.

Damodaran has developed a technique to turn dried and chemically stabilized fish proteins into a new class of hydrogels, the material that captures and holds moisture in diapers and scores of commercial products. The advance provides the first biodegradable hydrogel for diapers.

"The hydrogels on the market are made from petroleum and stand little chance of degrading over a reasonable time," Damodaran says. "Our studies have shown that the fish-based hydrogels get eaten up in a landfill within 28 days."

The fish-based material also holds its own compared to petroleum-based hydrogels, Damodaran says, and can absorb more than 400 times its weight in water. The petroleum industry makes about 800,000 tons of hydrogels annually.

The production process mixes ground fish with a chemical called ethylenediaminetetraacetic acid (EDTA), which adds water-binding molecules. The modified protein is then cross-linked with another chemical to create a "water-soluble matrix" that traps water in a gel. The final product is dried into powdered form.

Millions of tons of fish go to waste every year in commercial fishing and lake rehabilitation programs, and fish gels could turn a waste-disposal headache into a useful resource, Damodaran says.

About 50 percent of the catch from commercial ocean fishing gets chucked back into sea, he adds. On one large lake in southern Wisconsin, people harvest and dump 2 million pounds of carp annually from its waters.

The material may also work in hand lotions, filters and fertilizers, Damodaran says. For example, hydrogels could entrap pesticides and herbicides and allow their controlled release in the soil.

Incidentally, Damodaran says the fish gel is odorless, so fish diapers wouldn't be adding one unpleasant odor to another.

For more information, contact Damodaran at sdamodar@facstaff.wisc.edu.

Shining Light on Renewable Energy

In a step toward creating energy from sunlight as plants do, Massachusetts Institute of Technology (MIT) researchers have invented a compound that produces hydrogen gas with the help of a catalyst and a zap of light.

Professor Daniel G. Nocera of chemistry and former MIT graduate student Alan F. Heyduk, reported their discovery in the August 31, 2001 issue of Science. Creating a molecule to replace a leaf -- essentially, photosynthesis in a beaker -- could provide a cheap, clean future energy source, Professor Nocera said.

"We have been seeking a future alternative fuel source by studying the principles that govern the conversion of photon energy into chemical potential," he said. "Our strategy is to use the energy of sunlight to drive reactants uphill to energy-rich products, thus harnessing the sun's energy to create a renewable energy source in the future."

Nocera and Heyduk created a compound based on the metal rhodium. When the rhodium photocatalyst is dissolved in solution, the researchers add to it a hydrogen-containing acid (also called a hydrohalic acid -- one example is hydrochloric acid), and shine light on it.

"In the leaf, sugar and oxygen are energy-rich products. In our beaker, the sought-after fuels are hydrogen and a halogen, produced catalytically from the photochemical splitting of hydrohalic acid," Nocera said.

The structure of the rhodium compound allows it to break the hydrohalic acid's chemical bonds. Hydrogen gas, with a byproduct of bromides and chlorides, is produced. The byproducts are chemically trapped and recycled into the reaction.

While not as complete and efficient as photosynthesis, this system comes close to the ideal use of a molecular catalyst as part of a homogeneous reaction for which scientists have been searching for more than three decades.

The work is supported by the National Science Foundation.

For more information, visit web.mit.edu/chemistry/dgn/www/.

This article originally appeared in the January 2002 issue of Environmental Protection, Vol. 13, No. 1, p. 10.

This article originally appeared in the 01/01/2002 issue of Environmental Protection.