| Summary: | 碩士 === 國立中興大學 === 土壤環境科學系所 === 103 === Arsenic, a commonly found pollutant in the environment, has received much scientific concern because it, particularly in the inorganic form, is very toxic and carcinogenic to human. Arsenic consists of two major forms of As(III) and As(V). Since As(III) is more toxic than As(V), the oxidation of As(III) and subsequent removal of As(V) are considered an important strategy for treating arsenic contaminated sites. Fenton reaction, a well-known pathway of producing the OH radicals through the interaction of Fe(II) with H2O2 at an acidic solution, had been previously used to oxidize As(III). Recently, studies also find that zero-valent aluminum (ZVAl) exhibits an excellent efficiency of oxidizing As(III) in an aerobic system via a Fenton-like reaction. However, the presence of oxide layers on the surfaces of ZVAl would inhibit the OH radical productions, and a catalyst of polyoxometalates (POM) was used to remove the oxide layer and enhance the oxidant formation. The technique still needs some modifications because the POM is expensive and difficult to be recycled and reused. Thus, in the study, we tried to replace POM by Fe ions, including Fe(III) and Fe(III), in the ZVAl/O2 system to promote the Fenton-like reaction and enhance As(III) oxidation. In addition, Al beverage can (ABC) was also used as a substitute for ZVAl to investigate its potential efficiency for As(III) oxidation. Results showed that As(III) oxidation was indiscernible in the ZVAl/O2 system within the 360 min reaction; however, 80 μM As(III) could be completely oxidized in the ABC/O2 system within 120 and 360 min at pH 1 and 2, respectively. With the addition of Fe, 80 μM As(III) would be rapidly oxidized in both ZVAl/Fe(II)/O2 and ZVAl/Fe(III)/O2 system, and As(III) oxidation increased with an increase in Fe concentrations. During As(III) oxidation, the H2O2 accumulation was inhibited, a result demonstrating that Fe(III) could be reduced and reacted rapidly with H2O2 to promote As(III) oxidation. Besides, compared to ZVAl/Fe/O2 system, ABC/Fe(II)/O2 and ABC/Fe(III)/O2 system exhibited a higher oxidative ability at pH 1 and 2 because OH radicals could be produced through both Fenton and Fenton-like (i.e., H2O2 react directly with ABC) reactions. After As(III) oxidation, Al and Fe would co-precipitate with As(V), and 100% As(V) removal could be achieved when the solution pH was increased to 6.0. Because As associates commonly with Fe in the groundwater, the current results may provide a cost-effective method for treating As in the water body.
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