Abstract
Conventionally, oxidative treatment of mine-impacted water and acid rock drainage relies on biological methods, passive limestone beds, or chemical dosing, resulting in large treatment system footprints for passive systems and significant operating expenses for active treatment. Combining the benefits of conventional passive treatment systems with the high-strength of active treatment, H2nanO has developed a passive advanced oxidation (P-AOP) treatment technology consisting of a system of buoyant photocatalyst composites that provides off-grid, oxidative treatment without the need for chemical or electrical inputs. Driven by naturally occurring solar or artificial ultraviolet (UV) light, the photocatalyst technology generates free radicals, including hydroxyl and superoxide. As the photocatalyst media is not consumed, it may be collected for reuse (batch process) using low-energy flotation and skimming, or used continuously in a flow-through system.
Solar photocatalysis has been demonstrated at various scales for the removal trace elements using both natural sunlight and artificial UV, and the results are presented in this work. Herein, solar photocatalytic treatment was primarily implemented for the removal of dissolved iron and manganese through oxidative precipitation at circumneutral pH. For concentrations <10 mg/L, removal efficiencies of 95.3-99.6% were observed for dissolved iron and manganese. Simultaneously, co-precipitation and adsorption of additional trace metals was observed, including arsenic, nickel, and lead. These results will highlight the effectiveness of solar photocatalysis as a passive treatment technology for mine-impacted water management, whether as a standalone process or as part of a hybrid treatment system.