Removal of Arsenic 
and Other Heavy Metals from Water

Arsenic is a naturally occurring element in the environment. Arsenic in ground water is largely the result of minerals dissolving naturally from weathered rocks and soils.  Arsenic has many industrial uses such as hardening of copper and lead alloys, pigmentation in paints and fireworks, and the manufacture of glass, cloth, and electrical semiconductors. Arsenic is also used extensively in the production of agricultural pesticides, which includes herbicides, insecticides, desiccants, wood preservatives and feed additives. Runoff from these uses and the leaching of arsenic from waste generated from these uses has resulted in increased levels of various forms of soluble arsenic in water.

Inorganic arsenic is highly toxic to mammals and aquatic species. When ingested, it is readily absorbed from the gastrointestinal tract, the lungs, and to a lesser extent from the skin, and becomes distributed throughout the body.  Recently, arsenic in water supplies has been linked to arsenical dermatosis and skin cancer. 

 Because of recent studies further revealing its toxicity, the United States Environmental Protection Agency (EPA) has classified arsenic as a human carcinogen (Group A) and has promulgated regulations lowering its maximum contaminant level from its present requirement of50 parts per billion (ppb) to 5 ppb or less.

 GSA's process of removing arsenic employs a modified zeolite mineral, chabazite, product code ZS500As.  The modification involves exposing the zeolite material to concentrated ferrous aqueous solutions to form an iron-laden zeolite mineral, thereby greatly increasing the zeolites affinity for arsenic.  When contact is made between contaminated water and the zeolites, the zeolites act as sorbents, chemically bonding with the arsenic, which is then removed.  The media can be used in a column as a filter, or they can be prepared in powdered form and used in an existing water treatment plant.

 Advantages Over Other Processes 

Presently the ZS500As has a capacity of 2-2.5 g AsV/kg media and 8-9g AsIII/kg media. The effect of pH and the presence of sulfates appear to have little effect on the product performance.  Laboratory work is underway to test the performance of the media under a variety of possible industrial and municipal conditions.

The media has applications for other contaminants as well, most notable chromium. While the capacity of the media is not fully determined single column challenge tests on a solution containing 105 ppm CrVI treated over 442 bed volumes of solution with a minimum removal rate in excess of 97%.  Use of the product in multiple columns in series would increase the efficacy of the metals removal substantially.  A modification of the system increased its capacity to 2442 bed volumes with a minimum removal rate of 96%.

Test work underway by Physical Sciences, Inc. also shows an affinity for the removal of mercury in the gaseous form using a similar technology.  Material is being evaluated by a number of engineering companies, including a pump and treat at an abandoned pesticide facility, several mining operations and water utilities.

GSA Resources, Inc. has a diversified line of products uses for which the following Data Sheets are available:

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Last modified:  June 22, 2000