This study characterizes mine-drainage derived iron oxides as a precursor for the determination of potential reuses in sustainable water treatment processes. Pure iron oxides have been established as an effective sorptive media or coating for water treatment, yet iron oxides from mine drainages have largely been ignored as a source for this raw material. In addition to passive mine drainage treatment systems, environmental discharges of mine water and associated iron deposits were also examined. In total 13 sources of iron oxides were collected, these sources include 12 coal mining related discharges and one hard rock mining discharge. Water quality and dissolved metals data for the mine water were analyzed to aid in correlating site specific mine water conditions and dominant form of iron oxide present at each location. The iron characterization consisted of X-ray diffraction (XRD) analysis to determine the dominant form of iron, Munsell color classification, particle density, loss on ignition (LOI) to estimate organic matter, scanning electron microscopy (SEM) analysis to determine individual particle size, dry sieve particle size distribution (PSD) to attain ASTM particle size classifications, Brunauer-Emmett-Teller (BET) analysis of surface area, acid oxalate digestions (AOD) to determine the percent of crystalline and non-crystalline material, and inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis for metal concentrations in each iron oxide sample. Observed ranges of selected parameters are: Munsell color (5YR-10YR); particle density (1.97-3.04 g/cm 3); LOI (0.59-1.41%); SEM of smallest individual particles (5-20 nm); BET surface area (63.75-497.02 m 2 /g); AOD (13.52-96.31% non-crystalline material); and the iron content obtained from ICE-OES analysis ranged from (47 to 94% as goethite). The information gained through this detailed characterization of mine-drainage derived iron oxides may eventually aid in the future selection of appropriate iron oxides for sustainable reuse in water treatment processes.

Abstract. This study examines the potential to reuse mine-drainage derived iron oxides as anionic sorbents for sustainable water treatment purposes. Pure iron oxides have been established as effective sorptive media or coatings for water treatment processes; yet, iron oxides from mine drainages remain to be an abundant but unproven source of this raw material. Iron oxides from both passive mine drainage treatment systems as well as environmental discharges of mine water and their associated iron deposits were examined. Based on prior physical characterization, three samples were selected (according to their specific surface area) to evaluate their anionic sorptive capacities pertaining to naturally occurring concentrations of orthophosphate (1.13 ± 0.03 mg/L) in surface waters, and arsenate (117.79 ± 4.08 µg As/L ) in drinking waters. The mine drainage derived iron oxides' performances were compared against a commercial grade iron oxide product, Bayoxide E33 P at static pH values of 6.00, 7.00, 8.00, and 9.00 ± 0.10 standard pH units via laboratory scale sorption batch experiments. As a result of these experiments it was observed that the mine drainage derived iron oxides were more effective at contaminant removal than the commercial product. Promising contaminant removal efficiencies of up to 95% (arsenate) and 99% (orthophosphate) were documented at specific pH values for the mine drainage derived iron oxides, while adhering to virtually all US EPA primary and secondary drinking water standards; thus suggesting that it may be feasible to beneficially reuse mine drainage derived iron oxide in water treatment technologies.

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