Feasibility study for treatment of diesel-contaminated soil with persulfate

• Main Authors: Yi-Yu Guo, 郭奕妤
• Other Authors: Chenju Liang
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/3535gq

碩士 === 國立中興大學 === 環境工程學系所 === 99 === This study was to evaluate the feasibility of treating diesel contaminated soils with base and iron activated sodium persulfate (SPS) and dual oxidation system (H2O2/SPS). The alkaline source, lime (CaO) and sodium hydroxide (NaOH) and various factors including soil type, heat, reagent addition sequence and reaction time were also investigated in base activation system. Batch experiments were conducted using two soils (silica sand and sandy soil) spiked with diesel. Initial results showed that best diesel degradation was approximate 20% of diesel removal after 7 days of reaction time in the presence of either soil samples. Besides, no significant improvement on degradation of diesel was noted in the single or two-stage addition of SPS. The desorption of diesel from silica sand to aqueous phase was observed with addition of NaOH, but the observation did not occur with addition of CaO. In addition, it can be seen that diesel was mainly present as sorbed phase in the sandy soil system. Further experiments were carried out with elevated concentration of persulfate (from 0.1 M to 0.5 M) and extended reaction time (from 7 days to 14 and 28 days). Results revealed that about 30% of diesel removal observed after 28 days of reaction time. In summary, due to a low water solubility of diesel, the removal efficiency of diesel was not significant under all experimental conditions. Furthermore, the addition of surfactant (Tween 80) for increasing the solubility of diesel to enhance the treatment of diesel contaminated soil was evaluated. The optimal removal efficiency of 35% was achieved with 1.0% Tween and NaOH/SPS mole ration of 2.0/0.5. The results indicated that it was incapable to substantially increase the overall degradation efficiency of contaminants with addition of surfactant. The reason was due to competition between surfactant and diesel for oxidation. Pyrite as a ferrous source for activating persulfate was applied and 40% removal of diesel was reached with 0.5 M SPS and 6 g/L FeS2 for 3 days of reaction. However, since diesel can’t be effectively released to the aqueous phase, complete degradation of diesel was not achieved. Moreover, the best removal of diesel (about 56%) was achieved in dual oxidation system. Because of two strong oxidants involved in dual oxidation system, various radical oxidant species participated in degradation of diesel and resulted superior performance than other experimental conditions evaluated in this study.