Advanced heterogeneous fenton oxidation of 1,4-dioxane using zero-valent iron at neutral pH

Abstract

1,4-dioxane is currently used as a solvent in several industries. Conventional wastewater treatment technologies are ineffective for removal of 1,4-dioxane. Fenton oxidation process, one of the advanced oxidation processes (AOPs), shows high effectiveness for removal of organic contaminants. But traditional Fenton process has narrow working pH range (3~4), needs a lot of hydrogen peroxide, and there is no possibility of recycling the catalyst. In this study solid catalyst, zero-valent iron ($Fe^0$) was used to overcome limitations of traditional Fenton oxidation process. Oxidation of 1,4-dioxane using microscale $Fe^0$ was investigated with several major variables-presence of oxygen, initial pH, $H_2O_2$ dose and recycling of $Fe^0$ was also conducted. Nanoscale $Fe^0$ was synthesized and compared with microscale $Fe^0$ in removal efficiency. And ultrasonic irradiation was applied with Fenton process to enhance removal efficiency. In the presence of dissolved oxygen, $Fe^0$ generated $H_2O_2$ and remove 1,4-dioxane without an addition of oxidant. And removal remained efficient even at high pH. Wide working pH range implies that pH adjustment before treatment is not necessary. The formation of iron oxides did not obviously influence the activity of $Fe^0$ after recycling the used $Fe^0$. And ultrasonic irradiation greatly enhanced removal efficiency through enhancing generation of $H_2O_2$.