Column Leaching Of PAHs/heavy Metal In Soil By Surfactant And Chelating Agent

Soil is one of the most important natural resources on which human beings live. With thedevelopment of industrial and agricultural production, a variety of pollutants which cause soilpollution enter into the soil by atmospheric precipitation, sewage irrigation, application ofpesticides and many other ways. Soil pollution presents a big threat to the crop yield andquality as well as human and animal health, which has aroused people’s wide attention.Heavy metals and polycyclic aromatic hydrocarbons(PAHs) as typical representative ofinorganic pollutants and organic pollutants,removal of PAHs and heavy metals are verydifficult because of their low bioavailability and potential toxicity. It is effective to removePAHs and heavy metals by surfactants and chelating agents since surfactants can enhance theclean up of soils contaminated with PAHs by solubilization and chelating agents can desorbheavy metals from soil solid phases by forming strong water-soluble coordinationcompounds.This paper reviews the present soil pollution situation and the main repair methodtechnology, and selects the way of soil column leaching. The paper studies the TX100andTW80in pollution soil column before and after the adsorption behavior and residue. TX100and TW80different concentrations of PAHs contaminated soil leaching, and factors such aspH and inorganic salt on the surface active leaching effect. EDTA-2Na leaching of cadmiumin soil and its influencing factors. TW80and EDTA-2Na solubilization effect of pyrene, anddifferent elution sequence of composite pyrene-cadmium pollution soil leaching. In order toprovide technical reference to the research on compound soil remediation of heavy metals-PAHs.The main contents and results of the paper are as follows:(1)Study of surfactant TX100and TW80respectively adsorption behavior and residuein the pollution soil column or no pollution soil column, the results show that two kinds ofsurfactants on soil column adsorption ability are strong,and TX100adsorption ability isbetter than TW80, and adsorption quantity is greater than TW80,but TW80to reachadsorption equilibrium time shorter than the TX100, TW80to reach adsorption equilibriumat the time of2h, the TX100to reach equilibrium at4h. The PAHs pollute soil, not onlyincreased the adsorption of surfactants but also increased the surfactant adsorptionequilibrium time, increased about1times. The majority of Surfactant adsorption in thepollution soil or pollution soil can be washed with deionized water, the final residual fractionin soil column, and the residual amount is close.(2)The experiment comparatively studied the effect of leaching of TX100and TW80ofdifferent concentrations on the pyrene in the soil column respectively, and studied theinorganic salt and pH which had influence on surfactant elution of pyrene systematically. Surfactants TX100and TW80were good elution of pyrene, but the single non-ionicsurfactant elution of pyrene when the the single non-ionic surfactant elution had sameconcentration, the elution effect of TW80was better than that of TX100, for example, whenthe concentration was6000mg/L, the removal rate of pyrene by TW80and TX100were62.25%and59.06%respectively. Different pH value had a great influence on surfactantelution of pyrene, with the pH value increased from3to11, the removal rate of pyrenepresented a downward trend after first increasing, the removal rate of pyrene reached biggestwhen pH was7. Inorganic salt NaCl, CaCl2and MgCl2had inhibition on surfactant elution ofpyrene, the NaCl had few effect on the removal of pyrene the NaCl concentration was small,but with the increase of concentration, it can prompt pyrene leaching, when NaClconcentration was4000mg/L, the removal rate of pyrene reached67.18%, the removal rateincreased1.08times than that without NaCl, while CaCl2and MgCl2existed inhibitory effecton surfactant elution of pyrene, and with the increase of concentration of inorganic salt, theinhibition increased, but the inhibition of CaCl2was much bigger than that of MgCl2.EDTA-2Na existed inhibitory effect on surfactant elution of pyrene, but the inhibition wasstronger when in low concentration, with the increase of concentration of EDTA-2Na, theinhibitory effect weakened.(3) This study investigated the ability of leaching to elute cadmium from soil withvarying concentrations,and including the influence factor: CaCl2, NaCl and pH. Theconcentration of EDTA-2Na had a great influence on leaching, With increasing concentrationof EDTA-2Na, the elution of cadmium initially increased.Then With the increase of pH, theremoval rate decreased, when present in pH=5can be removed effectively.The Effect ofinorganic salt CaCl2and NaCl on cadmium is bigger, the inhibiting effect have a higherincrease at higher concentrations of inorganic salt, and CaCl2is far greater than the influenceof NaCl.(4) the solubilization effects of pyrene in the presence of TW80or EDTA-2Na and thecolumn leaching sequences for removing pyrene and cadmium in co-exist contaminated soilswas measured in this study. the experimental result was shown that TW80was more effectivethan EDTA-2Na to enhance pyrene solubilization. Desorption of pyrene or cadmium withTW80-EDTA-2Na, EDTA-2Na-TW80and TW80and EDTA-2Na mixed solution wasmeasured in the study. It revealed that the removal rates were definitely different comparetoTW80and EDTA-2Na mixed solution, TW80-EDTA-2Na and EDTA-2Na-TW80, thedesorption of pyrene reach a maximum value of56.38%,47.46%, and45.95%respectively,comparing with the value of5.18%with deionized water. But the desorption of cadmium wasdifferent with pyrene. The removal value was87.9%with EDTA-2Na-TW80;84.6%withTW80-EDTA-2Na;80.7%with TW80and EDTA-2Na mixed solution, comparing with thevalue of0%with deionized water. Thus, it comes the conclusions that TW80andEDTA-2Na mixed solution have the best desorption effect for remediation of pyrene in contaminated soil and the desorption effect for removing cadmium reach maximum valuewith TW80-EDTA-2Na. Thus, TW80-EDTA-2Na should be selected as the proper leachatefor remediation of pyrene and cadmium contaminated soil through integrated into account.