Removal and biodegradation of contaminated compounds in soil by inclusion in cyclodextrins and a slurry bioreactor

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To obtain the fundamental knowledge for the remediation of the contaminated soil by means of cyclodextrin, biphenyl was used as a model contaminated compound, and obtained the following results.1. The solubility of biphenyl in HP-β-CD has the highest value among various CDs. The association constant of biphenyl for HP-β-CD (CD) has the highest value, indicating that the CD has the potential ability of removing biphenyl from the contaminated soil.2. The adsorption isotherm of biphenyl was expressed by Langmuir equation.3. For the soil kneaded with CD, biphenyl released and dissolved markedly faster than without kneading. This implies that during kneading biphenyl in the soil was effectively included in CD and removed from the soil.4. To remove biphenyl included in CD, the kneaded soil was washed for a few times. After washing 3 times, biphenyl was totally removed from the soil when CD solution was used as the washing solution.5. Two types of biphenyl solution were incubated with an activated sludge under aerobic conditions : a perfectly included biphenyl solution with CD (included solution) and simply mixing solution. For the simply mixing solution, sudden decomposition of biphenyl was observed after 100 to 200 hours, while biphenyl in the included solution could be degraded surprisingly fast and was completely disappeared in 45 hours, about five times faster than in the simply mixing case.6. To simplify the treatment process and reduce the waste water, biphenyl in the kneaded soil with CD was directly treated by the activated sludge. The degradation rate of biphenyl was nearly equal to the included biphenyl. This implies that biphenyl in the kneaded soil would be perfectly included during kneading, and that the direct treatment of the kneaded soil by the activate sludge would be practical for the bioremediation of the contaminated soil.