Inexpensive, easy way to filter arsenic from water

Bin Gao's team used iron-enhanced carbon cooked from hickory chips, called biochar, to remove the toxin. He is an associate professor with the Institute of Food and Agricultural Sciences' in agricultural and biological engineering.

Arsenic is one of the most common environmental pollutants, finding its way into drinking water supplies through natural or humanmade sources and affecting millions of people worldwide. It has been shown to cause cancer and new methods to remove arsenic from drinking water and wastewater are urgently needed.

"Because biochar can be produced from various waste biomass, including agricultural residues, this new technology provides an alternative and cost-effective way for arsenic removal," Gao said.

In a study to be printed in the January issue of the journal Water Research, Gao and his team describe the process: The wood chips were first ground, then heated in nitrogen gas, but not burned. The resulting biochar, which has the consistency of ground coffee, was then treated with a saltwater bath to impregnate it with iron. Tests showed that plain biochar had no effect on arsenic, but the iron-enhanced product effectively removed the poison from water.

Current methods to remove arsenic include precipitation, adding lime or coagulants to water, using membranes to filter it out, or using an ion exchange process. But using a filter for removal is one of the most commonly used methods due to its ease of operation, relatively low cost and high effectiveness.

Gao said water treatment plants could use large biochar filters to extract the arsenic. Homeowners could use a small filter attached to their tap.

Additional investigations are still needed to optimize the process and to develop commercially available filters, he said. Gao's study was partly supported by the National Science Foundation.