(205b) Enhanced Oxidation of Toxic Organic Pollutants By Ferrate(VI) and Its Modifications in Aqueous Solution

Iron in oxidation state of +6, also known as ferrate(VI) (Fe(VI); Fe^VIO₄^2-), is receiving great attention as a multipurpose green chemical with a wide range of applications in different research areas such as organic synthesis, water and wastewater treatment, disinfection of viruses and iron batteries. In recent years, there has been an increasing interest in the application of Fe(VI) in water and wastewater treatment because of its unique oxidation, disinfection and coagulation properties (Fe(VI) is reduced to Fe(III) initiating coagulation). Although a lot of work related to the oxidation of pollutants by Fe(VI) has been reported, limited work related to the activation of Fe(VI) to decrease the required dose of the oxidant has been done so far. Fe(VI) could be activated by acid (e.g. HCl and HNO₃) to significantly enhance the oxidative transformation of caffeine (psychostimulant; CAF), acesulfame K (artificial sweetener; ACE) and atenolol (β-blocker; ATL) in aqueous solution, at a relevant to wastewater treatment pH range of 8.0-9.0 and room temperature. Almost complete removal of CAF and ACE by acid-activated Fe(VI) was achieved at Fe(VI) to CAF/ACE molar ratio of 8.0 and HCl to Fe(VI) molar ratio of ~1.5, in seconds to minutes. Interestingly, only ~60% removal of CAF/ACE by Fe(VI) (non-activated Fe(VI)) was achieved in hours. ATL was not removed by Fe(VI) at Fe(VI) to ATL molar ratio of 10.0. Importantly, around 30% ATL removal by acid-activated Fe(VI) was observed at the same Fe(VI) to CAF molar ratio (10.0) and HCl to Fe(VI) molar ratio of ~1.5. The effect of individual anions, cations and natural organic matter usually present in wastewater on the oxidation of CAF by acid-activated Fe(VI) and Fe(VI) (non-activated Fe(VI)) has been also investigated. Results showed that acid-activated Fe(VI) oxidation of CAF is not affected by ions. Interestingly, a negative effect on the removal of CAF by Fe(VI) (non-activated Fe(VI)) in the presence of calcium, magnesium and sulfate ions was observed. The oxidative transformation of CAF by both Fe(VI) and activated Fe(VI) decreased in the presence of natural organic matter. However, activated Fe(VI) could mineralize some of the other organic components present in natural organic matter indicating higher oxidation capacity of Fe(VI) upon activation. All in all, activated Fe(VI) technology is more efficient (lower dose of Fe(VI) required) and faster for treating water than Fe(VI) (non-activated), and it is not affected by common ions present in wastewater. The authors suggest that the findings of this study will be of great interest to the scientific community dealing with oxidation of pollutants in water and will initiate the investigation of the oxidation of a range of compounds by activated Fe(VI).