“Plastic Bottle” Solution for Arsenic-Contaminated Water Threatening 100 Million People

Newswise — DENVER, Aug. 31, 2011 — With almost 100 million people in developing countries exposed to dangerously high levels of arsenic in their drinking water, and unable to afford complex purification technology, scientists today described a simple, inexpensive method for removing arsenic based on chopped up pieces of ordinary plastic beverage bottles coated with a nutrient found in many foods and dietary supplements.

The report was part of the 242nd National Meeting & Exposition of the American Chemical Society (ACS), a major scientific meeting with 7,500 technical papers, being held here this week.

“Dealing with arsenic contamination of drinking water in the developing world requires simple technology based on locally available materials,” said study leader Tsanangurayi Tongesayi, Ph.D., professor of analytical and environmental chemistry at Monmouth University, West Long Branch, N.J. “Our process uses pieces of plastic water, soda pop and other beverage bottles. Coat the pieces with cysteine — that’s an amino acid found in dietary supplements and foods — and stir the plastic in arsenic-contaminated water. This works like a magnet. The cysteine binds up the arsenic. Remove the plastic and you have drinkable water.”

Tongesayi described laboratory tests of the plastic bottle arsenic removal method on water containing 20 parts per billion (ppb) of arsenic, which is two times the safe standard set by the U.S. Environmental Protection Agency for drinking water. It produced drinkable water with 0.2 ppb of arsenic that more than meets the federal standard.

The technology is so straight-forward that people without technical skills can use it, Tongesayi said, citing that as one of its advantages over some of the existing arsenic-removal technologies. It can use discarded plastic bottles available locally, and the application of cysteine does not require complicated technology. Tongesayi is seeking funding or a commercial partner, which he said is the key to moving the arsenic-removing process into use in a relatively short time. The technology also has the potential for removing other potentially toxic heavy metals from drinking water.

Odorless, tasteless and colorless, arsenic enters drinking water supplies from natural deposits in soil and rock that occur in some parts of the world, including parts of the United States, and from agricultural and industrial sources. Symptoms of arsenic poisoning include thickening and discoloration of the skin; stomach pain, nausea, vomiting and diarrhea; vision loss; and numbness in hands and feet. Arsenic also has been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver and prostate.

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Abstract

Arsenic is toxic to plants, animals and humans. It accumulates in living tissues because of its high affinity for proteins, lipids and other cellular components. Arsenic is also a carcinogen and exposure can lead to cardiovascular, pulmonary, immunological, neurological and endocrine disorders in addition to skin, lung, bladder and kidney cancers. Drinking water remains one of the most significant routes of arsenic exposure to humans. The recognition of the extent of arsenic toxicity resulted in the reduction of the maximum contaminant level (MCL) of arsenic from 50 ppb to 10 ppb. The reduction in the MCL of the metalloid requires that more efficient technologies for the treatment of arsenic in water be developed. Current technologies include membrane filtration, alum precipitation, iron precipitation, lime softening, coagulation and flocculation, adsorption and ion exchange, combination with iron (and manganese) removal, oxidation and adsorption, electrochemical treatment and solar oxidation. These technologies remain inaccessible to most communities in the developing world due to their cost and operational complexity. The main objective of this study was, therefore, to develop an effective but simpler, cheaper and environment-friendly method to remove arsenic from water. We attached cysteine molecules onto pieces of plastic cut from water bottles and used them to remove arsenic from synthetic water samples in a batch process. The method takes advantage of the high affinity of metals and metalloids by thiol groups. Arsenic, in the form of As (III), was removed to levels significantly lower than the current MCL for As of 10 ppb by at least an order of magnitude. Square wave cathodic stripping voltammetry was used to measure As (III).