For 50 million people living in South Asia, arsenic-contaminated groundwater poses a serious health problem. Case van Genuchten, a PhD student in Civil and Environmental Engineering, is working to see if rust can be part of the solution.
This problem is most severe in Bangladesh, where more than 40 million people drink arsenic-laden water. In some places, arsenic levels are more than 100 times the World Health Organization’s recommended upper limit of 10 parts per billion. Already arsenic poisoning is evident among 40,000 Bangladeshis. And without some kind of intervention, it is expected that arsenic poisoning will eventually cause 10% of deaths in this country of 140 million.
100L Electrode Assembly, the assembly of iron sheets that generate rust. This assembly will be used in a prototype that the team will be field testing this summer in West Bengal, India.
Conventional arsenic treatment methods are too expensive for nearly half of the people drinking arsenic-contaminated water. To address this need, the Berkeley Arsenic Alleviation Group (BAAG), of which Case is a part, aims to provide affordable, sustainable technologies that remove arsenic from groundwater. Their goal is to develop a technology that removes arsenic efficiently and cheaply and that can be easily operated and maintained by local communities. One of the two techniques for arsenic removal developed by Professor Ashok Gadgil at Lawrence Berkeley National Laboratory is ElectroChemical Arsenic Remediation or ECAR. In this process, iron is placed in water with high levels of arsenic, then electricity is used to dissolve the iron which produces rust. Arsenic is known to bind very strongly to the surface of rust particles. Consequently, rust — along with the arsenic bound to its surface — can be removed from the water through filtration or settling. ECAR requires only small quantities of iron—iron nails for example are sufficient—and such low amounts of electricity that it can be powered with a car battery or solar cells.
Standard ECAR Batch Test. This is how most of Case's ECAR tests are done, on a much smaller scale and with much smaller electrodes.
The goal of Case’s research is to understand ECAR’s reaction products; in other words, the formation of rust and its interaction with arsenic. The information he generates will reveal the mechanism for arsenic removal on rust and enable members of BAAG to determine the long-term stability of the waste generated through ECAR. To assess the arsenic-laden particles made in ECAR, Case uses Scanning Electron Microscopy and X-Ray Absorption Spectroscopy, which provide information on particle morphology, structure, and composition. Case’s research is driven by concern for the millions of people lacking access to safe drinking water and basic sanitation as well as a fascination with the chemistry of metals in aqueous systems. Fortunately, he’s found a project that satisfies both these interests.
This project has proved fortuitous in other ways too. An accidental discovery in the lab has added a promising new dimension to Case’s research. Although we’re most familiar with common orange rust, there are actually several different kinds of rust. When he began the project, Case’s focus was on orange rust. But one day in the lab, he noticed that instead of the typical orange rust his experiment was producing a rust so dark green it appeared almost black. His fear that he’d damaged the power supply wiring soon turned to curiosity when he saw that this new particle settled much faster than orange rust. Further testing revealed that Green Rust, which has a much larger particle size, settles in under an hour, a huge improvement over orange rust which takes several days to settle out. If this discovery pans out, it could eliminate the need for a filter or coagulant in future ECAR prototype designs, further reducing costs for this potentially life-saving technology.
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