Improving Mn(II) Remediation from Coal Mine Drainage by Passive 'Myco-Zeolite' Systems (thesis)

Abstract

Coal mine drainage (CMD) is a pervasive issue across Appalachia and contaminates watersheds and drinking water with difficult-to-remediate metals like manganese (Mn). Current passive treatment methods for remediating Mn from CMD include ponds with liner rocks like limestone to encourage the oxidative precipitation of Mn out of solution, but due to slow oxidation kinetics, Mn persists in many of these systems. This work explores the use of zeolites (to promote Mn removal from solution via adsorption) and Mn-oxidizing fungi (to promote Mn removal from solution via oxidative precipitation) to remediate aqueous Mn from CMD. Zeolite-only, limestone-only, and mixed liner rock systems reacted with a synthetic CMD (SCMD) as well as Mn-oxidizing fungi were examined. The solution was analyzed daily for aqueous Mn concentrations, and post-reaction, the solution was analyzed for a number of major and trace elements. Liner rocks were analyzed using scanning electron microscopy paired with energy dispersive X-ray spectrometry (SEM-EDS) and Mn K-edge X-ray absorption near edge structure (XANES) spectroscopy to determine chemical composition, spatial distribution, and average Mn oxidation state of the resulting solids. The research found that zeolites accelerate the removal of aqueous Mn(II) from solution in SCMD substantially compared to limestone systems. The addition of Mn-oxidizing fungi increases the average oxidation state of Mn overall and improves the overall extent of Mn remediation by the end of experiments. Biotic limestone systems are still the most effective remediators long-term, but the rapid kinetics of Mn removal from solution in zeolite systems is promising for the future of Mn remediation from CMD.