Purification of water contaminated with hexavalent chromium by carbonized seaweeds

Hexavalent chromium is a very harmful substance, and its contamination of water has been a serious issue for a long time. However, no simple and cheap methods of removing hexavalent chromium from water have been developed. To establish a simple and cheap removal method, the use of effective hexavalent chromium binders is essential. Some seaweeds are known to store heavy metals, suggesting that they contain specific substances that bind with heavy metals. In this study, we focused on the binding of carbonized seaweeds with hexavalent chromium. Among 36 surveyed seaweed species, a few brown algae showed high hexavalent chromium binding ability. We examined the hexavalent chromium binding ability of Wakame Undaria pinnatifida, and found that its hexavalent chromium binding ability depends on its fucoidan content. We also found that carbonized Wakame was effective for removing hexavalent chromium from wastewater of various cements, suggesting that carbonized Wakame could be used as an effective binder to remove hexavalent chromium present in wastewater from construction sites.