Nano-rust removes arsenic from drinking water

Nano-rust removes arsenic from drinking water

NEWS long-term plans to face challenges relating to the need, design, operation, maintenance, sustainable development and economics of not only desali...

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NEWS long-term plans to face challenges relating to the need, design, operation, maintenance, sustainable development and economics of not only desalination technologies, but also of the various possible tracks for water reuse. To achieve the goals set by the series of conferences that have been organized by ADST, this event aims to enhance the cooperation between countries in need of such technologies and those providing the knowhow, within the framework of a group of objectives. For example, it will review the current status of the regional needs for desalination, in light of the presently available alternative water resources, and evaluate the water requirements for those countries that suffer from water shortages. It will also report on developments in water and wastewater treatment using membranes and discuss future trends in pretreatment and post-treatment. Other topics include brackish water desalination; desalination in remote and arid areas; membrane bioreactor and associated technologies; desalination and the environment; and the management and economics of desalination systems. Contact: Conference Secretary, Alexandria University Desalination Studies and Technology Center, Alexandria University, Office of the President, University Administration Building, El-Shatby, Alexandria, Egypt. Tel: +203 591 1152, Fax: +203 591 4340, Email: [email protected], www.adst.sci.eg

Desalination plant to be built in Bermuda Consolidated Water Co Ltd has signed a contract with the Government of Bermuda to design, build and operate (DBO) a desalination plant on the north coast of Bermuda. The Tynes Bay Desalination Plant will process over 2250 m3 (600 000 gallons) of sea water per day, but its production capacity is designed to be increased to 4500 m3 (1.2 million gallons) per day at a later date. The project also

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includes a full standby electrical power plant and 2 km (1.27 miles) of main water delivery pipelines. The contract requires the company’s recently formed affiliate, Consolidated Water (Bermuda) Ltd, to construct and commission the plant and pipeline within 11 months and to operate the facility for at least 12 months after commissioning. The firm has entered into agreements to loan its Bermuda affiliate the funds to construct the plant and to manage its operations. Consolidated Water develops and operates sea-water desalination plants and water distribution systems in areas of the world where naturally occurring supplies of potable water are scarce or non-existent. It currently operates water production and/or distribution facilities in the Cayman Islands, Barbados, Belize and The Commonwealth of the Bahamas. The firm’s affiliate Ocean Conversion (BVI) Ltd also produces and distributes water in the British Virgin Islands. Contact: Consolidated Water Co Ltd, Regatta Business Park, Windward 3, 4th Floor, Grand Cayman, Cayman Islands. Tel: +345 945 4277, www.cwco.com

Nano-rust removes arsenic from drinking water The discovery of unexpected magnetic interactions between ultra-small particles of rust is leading scientists in the US at Rice University’s Center for Biological and Environmental Nanotechnology (CBEN) to develop a low-cost technology for removing arsenic from drinking water. The researchers say the technology holds promise for millions of people in India, Bangladesh and other developing countries where thousands of cases of arsenic poisoning each year are linked to contaminated wells. The new technique is described in a recent issue of Science (Vol. 314, No. 5801, pp. 964–967). ‘Arsenic contamination in drinking water is a global problem, and

while there are ways to remove arsenic, they require extensive hardware and high-pressure pumps that run on electricity,’ said lead author and the centre’s Director, Professor Vicki Colvin. ‘Our approach is simple and requires no electricity. While the nano-particles used in the publication are expensive, we are working on new ways of producing them that use rust and olive oil, and require nothing more than a kitchen with a gas cooker.’ CBEN’s technology is based on a newly discovered magnetic interaction that takes place between particles of rust that are smaller than viruses. ‘Magnetic particles this small were thought to only interact with a strong magnetic field,’ said Professor Colvin. ‘Because we had just figured out how to make these particles in different sizes, we decided to study just how large a magnetic field had to be in order to pull the particles out of suspension. We were surprised to find that we did not need large electromagnets to move our nano-particles, and that in some cases hand-held magnets could do the trick.’ The experiments involved suspending pure samples of uniformsized iron oxide particles in water. A magnetic field was used to pull the particles out of solution, leaving only the purified water. Colvin’s team measured the tiny particles after they were removed from the water and ruled out the most obvious explanation: the particles were not clumping together after being ‘tractored’ by the magnetic field. Professor Colvin says the experimental evidence instead points to a magnetic interaction between the nano-particles themselves. Co-author Doug Natelson, Associate Professor of Physics and Astronomy, explained: ‘As particle size is reduced the force on the particles does drop rapidly, and the old models were correct in predicting that very big magnetic fields would be needed to move these particles.’ ‘In this case, it turns out that the nano-particles actually exert forces on each other. So, once the handheld magnets start gently pulling on a few nano-particles and get things going, the nano-particles effectively work together to pull themselves out of the water.’

Professor Colvin said: ‘It is yet another example of the unique sorts of interactions we see at the nano-scale.’ Because iron is well known for its ability to bind arsenic, Professor Colvin’s group repeated the experiments in arseniccontaminated water and found that the particles would reduce the amount of arsenic in contaminated water to levels well below the US Environmental Protection Agency’s threshold for drinking water. Professor Colvin’s researchers have been collaborating with a second research group at Rice University, involved in civil and environmental engineering, to further develop the technology for arsenic remediation. Preliminary calculations indicate that the method could be practical for settings where traditional water treatment technologies are not possible. Professor Colvin says that because the starting materials for generating the ‘nano-rust’ are inexpensive, the cost of the materials could be quite low if manufacturing methods are scaled up. In addition, Professor Colvin’s graduate student Cafer Yavuz has been working for several months to refine a method that villagers in the developing world could use to prepare the iron oxide nanoparticles. The primary raw materials are rust and fatty acids, which can be obtained from olive oil or coconut oil, says Professor Colvin. Contact: Professor Vicki Colvin, Department of Chemistry, Rice University, 6100 Main Street, Houston, TX 77005, USA. Tel: +1 713 348 4082, Email: [email protected] ruf.rice.edu, http://cben.rice.edu

GE unit invests in French water purifier GE Energy Financial Services, a business unit of US-based General Electric (GE), has announced that it is entering the European water market and expanding into industrial water treatment by buying a majority of the assets of French company Idex Aquaservices.

Membrane Technology March 2007