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Modified Ferrihydrite for Enhanced Removal of Heavy Metals from MineWastewater
Primary Issue Addressed: Acid Drainage/Water Treatment
Secondary Issue Addressed: Active Treatments
Project Site: Montana Tech
Collaborating Entities: Montana Tech
Cost Share: None
Project Description
Ferrihydrite adsorption of dissolved heavy metals is widely used throughout the world. Researchers Twidwell and Hohn have previously demonstrated that arsenic can be more effectively removed from solution by adsorption/coprecipitation using aluminum-modified ferrihydrite (AMF) compared to using ferrihydrite. This project further explores the possibilities of AMF by investigating dissolved heavy metals (cadmium, copper, nickel, and zinc) removal by adsorption/coprecipitation with AMF. Specific objectives are to investigate the adsorption characteristics of ferrihydrite and AMF for removing dissolved heavy metals under conditions that vary with respect to the Fe/metal or Fe+Al/metal mole ratio, the aluminum/iron mole ratio in the AMF, and pH. Additionally, both room and elevated temperature aging tests will be employed to test the relative stability of metal loaded ferrihydrite and AMF.
Status
Work done to date includes running factorial design tests to determine the influence of the Fe/metal or Fe+Al/metal mole ratio, the aluminum/iron mole ratio in the AMF, and pH on the response variables (final cadmium, copper, nickel, and zinc concentrations). These tests indicated that there is very little, if any, difference in the adsorption/coprecipitation characteristics of ferrihydrite and AMF with respect to the dissolved heavy metals concentrations. Factorial design tests, focusing on ferrihydrite, have also been run to investigate the influence of pH and interactive effects of each metal on recoveries of each metal. These tests indicated considerable competition among the four metal cations for adsorption sites on the ferrihydrite. Room temperature aging studies have been underway since May 2005, and elevated temperature aging studies began in December 2005. The aging studies emphaisze ferrihydrite, but AMF samples are also included.
A final report, detailing the findings of project work is expected in fiscal 2006.