Pumping Iron

 

 

Iron and vitamin B12 are no longer just for dietary supplements. When bound together with a third material, they can break down some of the worst water pollutants, and they may thus be the key to restoring the health of the underground water supply.

Using these components, Prof. Brian Berkowitz and Dr. Ishai Dror of the Environmental Sciences and Energy Research Department (Faculty of Chemistry) have designed a treatment system that reduces the toxic chemicals in water to harmless compounds that can be further broken down naturally. Such a system could be placed in the path of underground flow to clean the water before it ever reaches the pipes, or it could be used to treat polluted water pumped from below ground.

Many of the waste chemicals that leach down into underground water reservoirs, called aquifers, can persist there for hundreds, even thousands of years. The problem, says Berkowitz, is that such man-made substances as pesticides, cleaning fluids and flame retardants don’t resemble anything found in nature, and thus few natural mechanisms exist to break them down. Unfortunately, many are considered to be carcinogenic even in extremely minuscule amounts, and Western standards allow only a few parts per billion of these pollutants to be present in drinking water.

Berkowitz and Dror realized that a simple chemical reaction might split the molecules of these harmful substances apart in such a way that bacteria or other natural processes could finish the job. The “indigestible” part of these molecules is generally a bond between a carbon ring and a chloride or bromide ion; if the reaction could get them to accept an electron in place of the ion, the two would be separated. As an electron source, the researchers turned to elemental iron, which easily gives up its electrons. They then looked for a way to combine the iron with a common filtering material called diatomite. Diatomite, though it resembles very fine white, powdery sand, is actually composed of fossilized diatom shells, and the microscopic pores in the grains make it an excellent filter for fluids – everything from swimming pool water to beer.
 

 

 

At first, the iron didn’t bind well to the diatomite base; and the electron transfer was only partially successful. The scientists realized they needed a further addition to the mix – a catalyst that would help get the electrons from the iron into the polluting molecules. “Rather than invent a new catalyst, we looked to natural molecules,” says Dror. “Nature’s favorite molecule for shuttling electrons is the porphyrin.” Porphyrins are found in everything from chlorophyll to hemoglobin to vitamin B12. The scientists found that B12 – an easily available, non-toxic substance – was just what the doctor ordered. The vitamin kept the iron particles small and spaced evenly on the diatoms’ surface, creating a large surface area for the chemical reactions to take place while enabling the water to flow through the material. Now the electron transfer was highly efficient. The costs of such a system, says Berkowitz, are comparable to those of standard activated carbon filters, and the results are much better, making them attractive to industries that rely on clean water.  

Larger diatomite/iron/B12 units could be placed in trenches or batteries of deep wells dug into the path of water flowing underground, says Berkowitz. In this way, aquifers that are in danger of contamination could be restored and their precious water reserves saved. Added advantages might include the prevention of soil contamination through seepage, a reduction in the need for such energy-intensive water-purification methods as desalination and a halt to the release of toxic gases from polluted aquifers into underground basements and parking garages.