Release of heavy metals from serpentine and heavy metals-polluted soils by chemical oxidation using persulfate

• Main Authors: Sih-Syuan Dai, 戴思瑄
• Other Authors: Zueng-Sang Chen
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/45317993999097662784

碩士 === 國立臺灣大學 === 農業化學研究所 === 105 === Persulfate is a common oxidant used for in situ chemical oxidation (ISCO), and it is usually activated by amendments such as Fe2+, EDTA-Fe2+ or alkaline to generate free radical which had higher redox potential to degrade the target pollutants. Serpentines soils contain high natural background concentrations of Cr, Ni and Co. However, Cr (VI) is carcinogenic and more mobile than Cr (III). Soil pH and Eh change after using ISCO and thus affect the mobility of heavy metals in soils. Three serpentine soils were collected from eastern Taiwan and anthropogenic polluted soils were sampled from Changhua county in western Taiwan. To explore heavy metals released from serpentine soils and polluted soils with different persulfate treatments, soils were spiked persulfate activated by two concentrations of Fe2+ and alkaline. The results showed that the concentration of remained persulfate decreased with time and generated H+ caused pH decreased, and thus increased heavy metals released. In this syudy, the polluted soils released 55.9 mg Cr/L, 59.5 mg Ni/L, 112 mg Cu/L, and 168 mg Zn/L were higher than serpentine soils because of the high level exchangeable fraction . Additionally, released Cr (VI) was higher from serpentine soils than polluted soils, and the alkaline activated treatment had highest content (5.9 mg Cr (VI)/L ) because of high pH value. Under the condition of this study, heavy metals may release more than in real condition because of higher concentration of persulfate remained. However, concerning about redox potential and Cr (VI) release, 105 mM Fe2+ activated treatment is better than other treatments because it had higher redox potential and Fe2+ may compete free radical and reduce Cr (VI).