Superfund Research Program


January 2024

Hot Publication

Taking a page from culinary arts, researchers at the Harvard University SRP Center, led by Paul Westerhoff, developed a new method inspired by French cooking to improve the ability of carbon block filters to remove arsenic from water. This technique may offer a cheaper and more practical solution for people to reduce arsenic exposure at the tap.

Carbon block filters are commonly used to treat water for pathogens or to remove unwanted tastes and odors. They are also used to remove organic contaminants from water but have not been effective at removing arsenic until now.

The study builds on earlier findings showing that adding titanium hydroxide to the carbon filters could trap arsenic. However, the earlier approach did not evenly distribute titanium within the filter and negatively affected water flow. To overcome these challenges, the researchers used an approach inspired by sous vide cooking techniques — which entail cooking food in a water-filled, vacuum-sealed container — to infuse commercially available carbon blocks with titanium hydroxide. In short, they removed air from the carbon block using a flexible pouch, added the titanium solution, sealed the pouch, and slowly heated the assembly in a water bath.

Compared to traditional autoclave heating methods, this approach uses 70% fewer chemicals, the researchers reported. Their technique also resulted in more uniform and stable distribution of titanium and did not affect water flow.

Next, they tested the ability of their modified carbon block filter to remove two common forms of arsenic from water — arsenate and arsenite. The team reported that the filter removed both types of arsenic from tap water containing either 10 or 100 micrograms per liter of the contaminant.

According to the authors, the new approach is particularly effective for removing arsenite, the more toxic of the two forms, and performs better than alternative filters when arsenic levels are low. Removing arsenic from water even when it is present at low levels is particularly important as there is no known safe level of arsenic exposure, they noted.

To learn more, please refer to the following sources:

  • Farsad A, Marcos-Hernandez M, Sinha S, Westerhoff P. 2023. Sous vide-inspired impregnation of amorphous titanium (hydr)oxide into carbon block point-of-use filters for arsenic removal from water. Environ Sci Technol 57(48):20410-20420. doi:10.1021/acs.est.3c06586 PMID:37948748