Characteristics and Mechanisms of Kaolinite‐Supported Zero‐Valent Iron/H2O2 System for Nitrobenzene Degradation

Abstract

Kaonilite‐supported zero‐valent iron (ZVI‐K) was employed with H2O2 to build a Fenton‐like system. Batch tests were conducted to explore the characteristics and mechanisms of the system for nitrobenzene (NB) degradation. The results showed that ZVI‐K was an efficient Fenton catalyst with several advantages, including an extended pH range to 7.02, a near‐neutral final pH of the treated water, and excellent stability and reusability. NB degradation was affected by initial pH, initial H2O2 concentration, and ZVI‐K dose. For NB concentration of 38.6 mg/L, their optimum values were 4.61, 170 mg/L, and 0.025 g/L, respectively. Under the optimal conditions, NB degradation reached 92% at 480 min reaction time via ZVI‐K reduction as well as homogeneous and heterogeneous Fenton reactions in the ZVI‐K/H2O2 system. During the first period of the treatments (<150 min), NB degradation was attributed by the reduction of ZVI‐K and heterogeneous Fenton reactions. However, both simultaneously occurred on the surface of ZVI‐K, thus affected each other and produced their antagonistic effects on each other. In the next period (>150 min), although limited amounts of iron were leached during NB degradation, the homogeneous Fenton reaction occurred, which benefited the ZVI‐K reduction. Thus, the synergistic effect between the Fenton reaction and ZVI‐K reduction occurred. Because all of these reactions simultaneously occurred and shared a synergistic effect, NB was degraded efficiently in the ZVI‐K/H2O2 system. Therefore, the system could be used to degrade NB.