HYDROXYL RADICAL FORMATION AND TRICHRLOROETHYLENE DEGRADATION IN PYRITE-CHALCOPYRITE DISPERSIONS

The increasing problem of wastewater containing persistent toxic organic compounds, such as Tricholoroethylene (TCE), is a serious environmental issue which requires powerful and energy-efficient remediation techniques. Advanced Oxidation Processes (AOPs) has emerged as promising strategy to remediate waters impacted by persistent organic contaminants. AOP involves chemical oxidation of pollutants through the in situ formation of Reactive Oxygen Species (ROS), particularly hydroxyl radicals (a strong oxidant). AOPs include UV mediated photocatalysis, solar visible irradiation, ozonation or electrolysis processes. However, due to complex installations and enormous energy consumption, these were replaced by more cost effective AOPs such as Fenton’s Reagent. Fenton’s Reagent consists of mixture of hydrogen peroxide (H₂O₂) and iron salts and generates hydroxyl radical (^•OH). However, injection of iron salts is problematic and H₂O₂ stability is limited to below pH 4. Use of minerals as a ferrous iron source alleviates these problems. Recent work has shown that pyrite (Py) degrades TCE in aerated solutions via the formation of H₂O₂ and ^•OH as part of the step-wise reduction of dissolved molecular oxygen.

Here we report on a study that evaluates the effect of combining chalcopyrite (Cpy) and Py mineral on ^•OH radical formation and their subsequent effect on TCE degradation. The addition of Cpy to a Py slurry leads to an enhanced production of ^•OH radical. The effect is non-linear and degrades TCE at a significantly enhanced rate. Further enhancement in TCE degradation is observed by treatment of these minerals with silver ions. The most pronounced enhancement of the degradation rate is observed with mixtures of silver-treated Py and Cpy. The exact mechanism of the non-linear rate increase in TCE is subject of an ongoing study. The results of this study indicate that combining Py and Cpy in AOP offers a pathway for accelerating the degradation of persistent organic molecules, such as TCE.

Intellectual Property protected by SBU Disclosure R-8542NTD.