Rapid As(III) oxidation mediated by activated carbons: Reactive species vs. direct oxidation

Activated carbon (AC) is widely used in pollutant removal, due to its adsorption capacity, conductivity and catalytic performance. However, few studies focus on the redox activity of AC and its role in pollutant transformation. In this study, we found that AC could efficiently mediate the oxidation of As(III) and the process of As(III) oxidation was pH and oxygen concentration dependent. In general, the presence of O-2 promoted As(III) oxidation at pH 3.0-9.5. Acidic and alkaline conditions favored As(III) oxidation regardless of whether there was oxygen, but the mechanisms involved were quite different when there was oxygen. At pH 3.0, reactive species (H2O2 and center dot OH) were generated and accounted for As(III) oxidation; at pH 9.5, As(III) was directly oxidized by O-2 (electron transfer from As(III) to O-2 mediated by carbon matrix) under aerobic conditions. Pre-oxidation and cyclic experiments results indicated the ability of AC to oxidize As(III) at pH 9.5 was sustainable and recyclable. This study provided a new insight in pollutant oxidation by AC in the environment.

Automated summary

Activated carbon (AC) is commonly used for pollutant removal due to its adsorption capacity, conductivity, and catalytic performance. This study found that AC can effectively mediate the oxidation of As(III) and the process is pH and oxygen concentration dependent. At pH 3.0, reactive species (H2O2 and center dot OH) contribute to As(III) oxidation, while at pH 9.5, As(III) is directly oxidized by O-2 via electron transfer from As(III) to O-2 mediated by carbon matrix under aerobic conditions. Pre-oxidation and cyclic experiments show that AC's ability to oxidize As(III) at pH 9.5 is sustainable and recyclable. This study provides new insights into pollutant oxidation by AC in the environment.