Ultrasonic-surfactants Washing High Concentrations Of Petroleum Contaminated Soils

Petroleum is a kind of important resource, which is widely used and brings pollutions into the soil environment. Most of petroleum hydrocarbons are hydrophobic compounds, which are low in water solubility and persist in soil environment for a long time. They destroy the nature and function of soil and become the persistent pollution sources of surface water and underground water. Besides, the hydrophobic nature of petroleum pollutants limits biodegradation and other remediation technology heavily. Therefore, increasing the solubility of hydrophobic hydrocarbon pollutants, which can transfer them from soil to water, is the key process of remediation of oil-contaminated soil.Surfactants are special compounds that are both hydrophobic and hydrophilic. They can increase water the solubility of hydrophobic compounds significantly through micelles partition and interfacial tension changes. As a result, surfactant washing is a promising technology for removal of petroleum from contaminated soils and draws great attention.The work of this study is divided into two parts, laboratory and device pilot experiments. In the laboratory, several anionic and nonionic surfactants were selected to remove petroleum from contaminated soils in Shengli Oil Field. The effect of different systems with various mass ratios of anionic and nonionic surfactants and condition parameters on removel efficiency was investigated. Device is mainly design and manufacture pilot test, and the device to actual repair parameters of a series of optimization experiment for practical engineering repair, laid a certain foundation.The principal conclusions were as follows:When the common surfactants were used to wash the contaminated soils, the optimum condition was mixed surfactants of SDS and TW20 with a mass ratio of 5:5, total surfactant concentrations of 2 g/L, assistant washing agents sodium silicate concentration of 6 g/L, solid-liquid ratio of 1 g/20 mL, and a temperature of 75℃for an hour. The removal rate reached 76.31%. Three time washes could increase the removal rate to 84.77% and decrease the petroleum hydrocarbons content in soil from 32.16% to 4.89%. The results from wash water reusing experiments showed that the wash water which contained surfactants and assistant agents still had the ability to remove petroleum hydrocarbons. Wastewater reuse can not only reduce the cost of cleaning and reduce environment pollutionThis paper also examines the under different temperatures of ultrasonic and stirring petroleum contaminated soil samples cleaning effect, the results showed that ultrasonic assisted cleaning could narkedly improve cleaning effect.This was based on the cavitation and ultrasonic cleaning effect, make liquid pressure changes and rapidly forming countless tiny vacuum bubble and rapidly implosion, the moment can produce powerful impulse energy that can damag the adhesion of oil hydrocarbons and soils, then have oil hydrocarbons easily taken off with soils.Pilot test showed, designed and manufactured by pilot test devices on petroleum contaminated soils do have good cleaning effect on soil petrochina, to be denitrogenized and recovery purposes. The optimum condition was LAS quality concentration of 2.4 g/L, TX100 mass concentration was 0.6 g/L, assistant washing agents sodium silicate concentration of 5 g/L, solid-liquid ratio of 1 g/20 mL, and a temperature of 75℃for ultrasound 30 minutes, mixing 60 minutes. The removal rate reached 65.80%, and decrease the petroleum hydrocarbons content in soil from 32.16% to 4.89%, next to the soil biological repair.Analysis of infrared and uv-visible spectroscopic data gave that surfactants were effective to remove four groups of petroleum hydrocarbons. The pilot test cleaning effect also have reached pilot test requirements, obviously decreased the severe petroleum contaminated soils of petroleum hydrocarbons pollutants. This paper verified the cleaning methods established the reliability and designed and manufactured by the feasibility of the pilot test, and contributed to practical remediation.