Research pick: Adsorbing arsenic - "Development of modified kaolins for the removal of As (III) in waters"

Back in the early 1990s, this author first heard about an insidious environmental disaster unfolding on the Indian subcontinent. Once insoluble arsenic salts were being exposed to the atmosphere when aquifers were drained for irrigation, becoming oxidized to a soluble form, and then being carried into the drinking water tapped from those aquifers once they refilled. The problem had first been unearthed by K.C. Saha, a government dermatologist from what was then known as Calcutta in the early 1980s. Scientists from Jadavpur University and Dhaka Community Hospital spent many years attempting to draw attention to this invisible killer affecting millions of people and this author attempted to bring awareness to the plight at the time through the western media.

The problem still exists despite ensuing international efforts to address it. Arsenic poisoning leads to startling visible symptoms: tell-tales skin problems such as melanosis, keratosis, and skin cancer, inflammation of the eyes, gangrene and skin growths, and can ultimately be lethal. There have been numerous attempts to develop ways to precipitate the solubilised arsenic from well water so that it might be filtered easily with varying degrees of success. In subsequent years, the problem has been revealed to be a far more widespread problem, being seen in various parts of Southeast Asia the Americas, and elsewhere.

New work published in the International Journal of Environment and Health, by a team from Argentina has looked at how modified kaolins might be used to remove dissolved arsenic(III) salts from water.

Estefanía Baigorria, Leonardo Cano, and Vera Alvarez of the Universidad Nacional de Mar del Plata and Karim Sapag of the Universidad Nacional de San Luis, explain how iron-containing clays are known adsorbents of dissolved arsenic. They have now impregnated natural and acid-treated kaolinites with iron oxide and demonstrated 97 percent effectiveness with one such material impregnated to 30 percent iron oxide within an hour. After a prolonged exposure 100 percent reduction of arsenic content is possible.

As such, the team recommends further investigation of these modified materials as a possible solution to the problem of arsenic-contaminated water.

Baigorria, E., Cano, L., Sapag, K. and Alvarez, V. (2020) ‘Development of modified kaolins for the removal of As (III) in waters’, Int. J. Environment and Health, Vol. 10, No. 2, pp.116–132.