A Study On Degradation Of Trichloroethylene In Fenton System With Nano Zero-valent Iron

With rapid economic development and sharp population growth, the demand for groundwater resources continues growing in the process of human life and production. Meanwhile, the problem of groundwater pollution comes along with large use of groundwater. Trichloroethylene(TCE) as typical chlorinated organic contaminants, was paid close attention in groundwater pollution. In recent years, researchers found that nano zero-valent iron(n ZVI) could be used for in site environment remediation. Compared with traditional zero valent iron, n ZVI has more specific surface area and reactivity, which shows faster reaction rate and fewer reaction by-products in the process of environment remediation. As n ZVI has highly reactivity, it is easy to form iron oxide and/or iron hydroxide shell, especially when it gets in touch with oxygen and/or water. Although these natural core-shell structure limits reactivity of n ZVI in some conditions, shell could provide source of ferrous and ferric iron which were indispensable in Fenton system. Hence, core-shell structure of n ZVI may be applied to in site environment remediation as a heterogeneous catalyst in Fenton system. In this paper, core-shell structure of n ZVI as a heterogeneous catalyst in Fenton system was used for degrading high concentration TCE. Meanwhile, benzoic acid(BA) as chemical probe was used for capturing hydroxyl radical which could quantificationally measure the oxidizing capacity of n ZVI in Fenton system. Core-shell structure of n ZVI characterizations came from XRD, TEM and XPS analysis before and after reaction. In our experiments, initial p H condition may have influence on Fenton system. Compared with magnetite nanoparticles(MAG) in Fenton system, this study is focused on mechanism discussion about core-shell structure of n ZVI in heterogeneous Fenton catalysis reaction and could contribute to practical application for core-shell structure of n ZVI in situ environment remediation. The main research results are as follows:1. All of TCE could be rapidly degraded in Fenton system with core-shell structure of n ZVI in acid or neutral condition.2. BA as chemical probe, this study found that Fenton system with core-shell structure of n ZVI mainly produce hydroxyl radical to oxidatively degrade TCE.3. Initial p H condition could have influence on oxidizability of Fenton system, and acidic condition is better than near-neutral condition. Core-shell structure of n ZVI in Fenton system makes for extending p H range of working Fenton system.4. Core-shell structure of n ZVI was mainly used as a solid catalyst in heterogeneous Fenton reaction. Fe3O4 of shell could provide source of ferrous and ferric iron which were indispensable in Fenton system, and Fe0 of core provide electron via core to shell which could promote Fenton reaction cycle. Compared with magnetite MAG in Fenton system, core-shell structure of n ZVI in Fenton system has an advantage on in site environment remediation.