Removal Of PAHs From Contaminated Soil By DOM Derived From Fructus Gleditsiae Sinensis And Its Influence Factors

This thesis carried out the following four studies:1) Adsorption kinetics of phenanthrene and pyrene in red soil and black soil as well as the effects of DOM derived from Fructus Gleditsiae Sinensis (DOM-FGS) on the desorption behavior of phenanthrene and pyrene from the two type of soils.2) Removal of phenanthrene, pyrene and copper from contaminated soils by DOM-FGS, as well as the interactions among phenanthrene, pyrene and copper.3) Effects of aging time on the removal of phenanthrene and pyrene from contaminated soil by DOM-FGS.4) Influence of DOM-FGS on the leaching of PAHs from soil column. The following are the main results.1) The adsorption equilibrium time for phenanthrene and pyrene in red soil were both 15 min and the adsorption rates of phenanthrene and pyrene were 94.2% and 98.8%, respectively. The adsorption equilibrium time for phenanthrene and pyrene in black soil were 6h and 4h, respectively. And the adsorption rates of phenanthrene and pyrene were 99.1% and 99.7% respectively in black soil. The desorption rate of phenanthrene from red soil increased with the increasing concentration of DOM-FGS. When the concentration of DOM-FGS was 0.04%, the desorption rate of phenanthrene was 1.23 times of the control with deionized water. Comparing with deionized water, DOM-FGS had no effect on the desorption rate of pyrene from red soil (p< 0.05). The desorption rates of phenanthrene and pyrene from black soil increased with the increasing concentration of DOM-FGS. When the concentration of DOM-FGS was 0.04%, the desorption rates of phenanthrene and pyrene from black soil were 1.6 and 10.8times of the control with deionized water, respectively.2) When the concentration of DOM-FGS was 1%, the removal rates of phenanthrene and pyrene from contaminated soils were 21.2% and 14.5% respectively. The removal rates of phenanthrene and pyrene from contaminated soil increased with the increasing concentration of DOM-FGS. When the concentration of DOM-FGS was 5%, the removal rates of phenanthrene and pyrene from contaminated soils were 59.2% and 53.1% respectively. The PAHs removal capabilitiy of DOM-FGS was lower than that of Tween 80 but higher than that of rhamnolipid. Considering the wide distribution of Gleditsiae Sinensis, the convenience of the preparation of DOM-FGS, and the natural and pollution free properties of DOM-FGS, great potential applications of DOM-FGS can be expected as a removal agent of PAHs from contaminated soils. Not only the separate removal of PAHs or copper, but also the simultaneous removal of phenanthrene, pyrene and copper from contaminated soils can be enhanced by DOM-FGS. When the concentration of DOM-FGS was 5%, the removal rates of phenanthrene, pyrene and copper were 53.1%, 49.7% and 54.4% respectively, indicating the potential applications of DOM-FGS for remediation of complex contaminated soils.3) The removal rates of phenanthrene and pyrene from contaminated soils by DOM-FGS first increased and then decreased with the aging time. There was a significant positive correlation between the concentration of DOM-FGS and the extraction rates of phenanthrene and pyrene from contaminated soil (R2> 0.95), which indicated that the removal rates of phenanthrene and pyrene from contaminated soils increased with the increasing of the concentration of DOM-FGS. Considering the wide distribution of Gleditsiae Sinensis, the convenience of the preparation of DOM-FGS, and the natural and pollution free properties of DOM-FGS, great potential applications of DOM-FGS as a removal or extracting agent of PAHs from contaminated soils can be expected.4) DOM-FGS have an inhibitory effect on the desorption of phenanthrene, but not pyrene, from contaminated soils when its concentration was very low. When the concentration of DOM-FGS was 0.01%, compared to deionized water controls, the desorption rate of phenanthrene from contaminated soil was suppressed by 87.9%. The desorption rates of phenanthrene and pyrene from contaminated soil and their migration quantities in soil column increased with the increasing of the concentration of DOM-FGS. When the concentration of DOM-FGS was 1%, the desorption rates of phenanthrene and pyrene from comtaminated soils were 38.7% and 27.9% respectively. Desorbed phenanthrene and pyrene can migrate down to 10cm in depth in soil column with DOM-FGS. However, the main part of them remained in the 0-2 cm soil layer. The content of phenanthrene and pyrene in 0-2 cm soil layer as percent of the total amount of phenanthrene and pyrene desorbed from the contaminated soil was 89.4% and 86.6% respectively. The percentage of phenanthrene and pyrene in other soil layers (2 cm per layer) were all less than 5%.