Iron slag/sludge agent induced Fenton-like reactions for treating chlorinated benzene compounds contaminated soil

• Main Authors: Zong-HanLi, 李宗翰
• Other Authors: Juu-En Chang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/91230228802991865442

碩士 === 國立成功大學 === 環境工程學系碩博士班 === 100 === An-Shun plant of China Petrochemical Development Corporation (CPDC) has been given much attention globally because of its highly contaminated soil by dioxins, mercury, and pentachlorophenol, and the contaminated area was estimated about 40 hectares. This study mainly focused on the decomposition of dioxins due to their high toxicity, persistence, and bioaccumulation. Besides, some studies indicated that dioxins can pass through the food chain causing hazard to health. It has been proved that dioxins can be decomposed efficiently by hydroxyl radicals generated from Fenton and Fenton-like reactions, which are driven by mixing ferrous ions or iron oxides with hydrogen peroxide (H2O2). On the other hand, iron slags/sludges are by-products of steel-making processes, so that they contain large amounts of iron or iron oxides, possessing the potential as iron sources of Fenton-like reactions. In this study, Fenton and Fenton-like reactions were used to treat soil contaminated by 4-chlorophenol (4-CP) and dioxins. Besides, iron slag/sludge agents (ISA) produced from iron slag/sludges were used in Fenton-like reactions to achieve the goal of destruction of organic pollutants in soil from An-Shun plant. From the results, ISA produced from magnetic iron slag/sludges was suitable for the Fenton-like reactions because of their high iron content and low acid neutralization capacity. The results of the degradation of 4-CP contaminating soil suggest that ISA are feasible iron sources for Fenton-like reactions, and both Fenton/Fenton-like reactions are suitable for treating 4-CP contaminating soil. With [4-CP] = 1500 mg/kg, the optimal conditions for Fenton reactions were pH = 3, [ferrous sulfate] = 9 mM, and [H2O2] = 29.41 mM. Furthermore, an 100% removal efficiency was achieved in 30 min. For Fenton-like reactions, the optimal conditions were pH = 3, [ISA] = 100 g/kg, and [H2O2] = 73.53 mM, and an 100% removal efficiency was also achieved in 30 min. The analysis of fourier-transform infrared spectrometer (FT-IR) and the concentration of chlorine ions showed that the chlorine bonds and aromatic ring can be decomposed by Fenton/Fenton-like reactions. The concentration of dioxins (Cdioxins) was the highest for the soil from An-Shun plant with particle size less than 0.062 mm, and lower for 0.25～2 mm, then 0.062～0.125 mm, and the lowest for 0.125～0.25 mm. The main compounds of dioxins were OCDD, OCDF, 1,2,3,4,6,7,8-HpCDD and 1,2,3,4,6,7,8-HpCDF. In addition, the R2 value between total organic carbon (TOC) content and Cdioxins of soil is 0.709, meaning the binding capability of soil and dioxins is affected by TOC content. The optimal conditions for treating dioxins contaminating soil with Fenton reaction were pH = 3, [ferrous sulfate] = 6 mM, and [H2O2] = 15%, and a 63% removal efficiency is achieved in 24 hours. For Fenton-like reaction, the optimal conditions were pH = 3, [ISA] = 100 g/kg, and [H2O2] = 10%, and a 68% removal efficiency was achieved in 24 hours.