Experimental Study On Leaching Remediation Of Petroleum-contaminated Soil In Surfactants

Petroleum accounts for about 40% of the total energy consumption in the world, which is widely used in transportation, petrochemical and many other industries. With the increasing of amounts of exploration and use, a large amount of petroleum and its products enter into the environment. And their unreasonable use and inappropriate disposal have caused a series of petroleum pollution accidents causing serious soil environment pollution.Leaching technology in surfactants is very promising in the remediation of petroleum-contaminated soil which has been widely studied at home and abroad. When the contaminated soil is treated after being mixed with surfactant solutions, the soil pollutants will transfer from the soil phase to the liquid phase through the unique amphiphilic structure and solubilization of surfactants. And then the leaching wastewater will be treated and the remediation on petroleum-contaminated soil has been completed.The leaching effect in water was firstly investigated by orthogonal experiments and secondly the effect on removal efficiency of petroleum pollutants in various leaching solutions and different leaching conditions were studied. In addition, the leaching effect in single and mixed surfactants were compared and analyzed. Finally, column experiment were conducted for dynamic simulation and ultimately the optimal surfactant and leaching conditions were determined. The research results are shown as below:1. In the process of leaching remediation of petroleum-contaminated soil in surfactants, the removal rate of pollutants can be improved when the surfactant is changed, the surfactant concentration is increased, the oscillation temperature is increased, the time of oscillation is prolonged, or the solid-liquid ratio is increased and so on. The removal rate is not positively correlated with each factor, but there exists an optimal value in the selected range.2. In the orthogonal experiment of water leaching, oscillating temperature is the main influencing factors by range analysis, and the second is oscillation time with the least influence of solid-liquid ratio. The optimal combination is: oscillation temperature of 60℃, oscillation time of 75 min and solid-liquid ratio of 1:20.3. The optimum leaching conditions of single anionic surfactant LAS and SDS,single nonionic surfactant Tw 80 and mixed anionic- nonionic surfactant LAS-Tw 80 and SDS-Tw 80 are determined. Comparative analysis shows that mixed LAS-TW 80 does not have the synergistic effect, but SDS-Tw 80 mixed system has synergistic effect, because SDS can in a great extent prevent Tw 80 from being strongly adsorbed in the soil.4. In the column leaching experiment, removal rate of petroleum pollutants decreaces with the increase of the sampling height. Removal rates in sampling port are almost the same after 4h and they increase rapidly during 4-8h, finally, they all tend to be stable. In addition, with the increase of surfactant solution, the amount of petroleum pollutants washed out by per unit volume gradually decreases.