HEXAVALENT CHROMIUM REDUCTION BY MINERAL OLIVINE

Hexavalent chromium (Cr(VI)) is toxic and generally mobile in groundwater, unlike Cr(III) which is nontoxic and typically precipitates out of the water. Zerovalent iron (ZVI) is commonly used in groundwater remediation to reduce Cr(VI) to Cr(III). This study was designed to investigate whether mineral olivine (which has historically been commercially mined in western North Carolina) could be employed as a reducing agent in the remediation of Cr(VI).

Batch experiments were conducted by mixing <0.5mm-diameter olivine (0.025-4.0g) with 10mL DI water, Cr(VI) solutions (50-1000ppb) and measuring the chromium remaining in solution. Samples were analyzed for Cr(VI) using the colorimetric diphenylcarbazide method, and total chromium was measured with AA spectrometry. Initial results show Cr(VI) of about 100μg/g olivine; experiments using 1000ppb Cr(VI) solutions had >90% reduction with >0.1g olivine, and >99% with 1g. Future work is planned to investigate the impacts of grain size and olivine composition (iron content) and compare to results using commercially-obtained ZVI.