Sorption onto and Recovery of Cr(VI) Using Iron-Oxide-Coated Sand

A new adsorbent media has been prepared consisting of iron oxide coated onto sand surfaces. The oxide coating is made by adding a solution of a ferric salt and base to a mixture of sand and applying various heating protocols. The iron oxide is an excellent, regenerable adsorbent, and the process of coating it on sand allows the media to be used in a packed column. Depending on solution pH, the media can be made to adsorb either cationic or anionic metals. In this work, the media was used to collect hexavalent chromium from a synthetic waste stream. The influent contained 20 mg/L Cr(VI), and better than 99% removal was achieved consistently. Once breakthrough occurred, the media could be regenerated by exposure to base. The pH of the regenerant solution determined the kinetics and efficiency of the regeneration process. With further development, the process represents an inexpensive and effective method for removal and recovery of metals from industrial waste streams.