Contaminant removal

15 January 2009

Berkeley chemistry professor, Matt Francis, and his colleagues have developed a hydrogel material that can detect and remove contaminants in water.

The hydrogel shrinks as it absorbs heavy metal pollutants, signalling the presence of cadmium and other toxic ions, even as it absorbs them from the contaminated water.

Better yet, the hydrogel specifically targets and removes these toxic ions even from sources such as brackish water that are loaded with sodium, potassium and magnesium ions.

After contamination, the hydrogel can be flushed with inexpensive chelating (metal binding) agents and reused.

The hydrogel material consists of polymer coils held together by strands of metallothioneins - proteins that bind to the copper, zinc, cadmium, mercury, chromium, and arsenic ions that can poison water supplies.

Francis said: 'The material was found to bind cadmium ions in the largest amount, followed by copper and mercury ions. In the case of cadmium, the hydrogel was found to bind up to 4.5 per cent of its dry weight in metal ions.'

For now, the researchers foresee the hydrogels being used primarily for testing, not for large-scale municipal water purification.

The metallothionien they chose was derived from pea plants and was expressed in E. coli bacteria in small quantities.

With large fermentation facilities, the production process could be scaled to yield much larger quantities at relatively low cost.