Preparation Of New Type Of Desorption Agent And Its Application Inpetroleum Contaminated Soilsin Oilfield

With the increase of the production and consumption, petroleum has become one of the most important energy. The environmental problems caused by petroleum and petroleum products during the process of mining, refining and storing has became more and more serious. With the development of petroleum industry in China, more amd more soil in oilfield was contaminated by petroleum resulted in the degradation of soil ecological function and the damage of biodiversity. Thus, the remediation of petroleum contaminated soil is necessary. Considering that the petroleum is a hydrophobic organic compound, which can exists in the soil for a long time, it is necessary to take special measures to repair it. Nowadays the surfactant-enhanced remediation has been suggested as a promising technology for the remediation of contaminated soils. This paper chose five different surfactants as experimental subjects to repair the petroleum contaminated soils. According to the analyses of the adsorption characteristics of surfactants on the soil surface and its influential factors, one appropriate surfactant could be figured out. Besides, the paper also investigated the separation of desorption agent and the stripping condition. Results indicated that:1. The adsorption kinetics of SDS、SDBS could be described by using the kinetics of level 1; the adsorption kinetics of TX-100、Tween80 could be described by using the kinetics of level 2; the adsorption kinetics of saponin could be described by using the internal diffusion model. The adsorption equilibrium of five kinds of surfactant was in 2 hours andthe adsorption quantity of Tween80 in coastal saline soil was the highest, getting to 6.89 mg g-1, and that of saponins in coastal saline soil was at smallest, just 2.17 mg g-1. The adsorption isothermal curve of SDS、TX-100、 saponin could be described better by using Sips model on the Tianjin coastal saline soil.The adsorption isothermal curve of compound desorption agent showed that the soil could reduce the quantity of one kind of surfactant through the addition of another kind of surfactant. When pH increased from 2 to 10, soil adsorption quantity of SDS and TX-100 decreased constantly, for saponin, howecver, no significant difference was observed; the adsorption quantity of TX-100, SDS, saponin all increased when temperature increased from 10℃ to 50℃. We finally choose SDS, TX-100, saponins as surfactant for subsequent tests based on the above experiments.2. Batch experiments were conducted to study the optimum stripping conditions of petroleum-contaminated soil at the condition of different concentrations of sodium silicate (1 g L-1,3 g L-1,5 g L-1), different temperatures (50℃,60℃,70℃), and different vibration times (40min,50min,60min). The optimal flushing conditions was established based on principles of chemical heat washing, as well as orthogonal experimental design, i.e. Sodium silicate,5 g L-1; temperature,70℃; vibration time, 50min. Results showed that under optimal flushing conditions, the efficiency of SDS/saponin mixed surfactant for the removal of petroleum from the contaminated soils were greater than that of SDS, TX-100 and SDS/TX-100 mixed surfactants, respectively. The SDS/saponin mixed surfactants had a removal rate of 84.35% of petroleum at its mass ratio of 5:5 and total concentrations of 1 g L-1,15～20% greater than SDS/TX-100 mixed surfactants. The experiment of separation and recovery of stripping agentshowed that the soil and stripping liquid still had a small amount of residualstripping agent after stripping, and the residual quantity of SDS/saponin mixed surfactant in soil was lower than that of SDS/TX-100 at the same concentration, which was dropped from 2537 mg kg-1 to 1769 mg kg-1 after washing for three times. Results suggested that using of organic solvent effectively remove the petroleum from the stripping liquid. Chloroform had the best removing effect that reached 78.36%,and the removing effect of n-hexane was the worst, with only 69.27%.3. The experiment of optimization of desorption process showed that it could get the best stripping effect under the optimal pH, concentration and vibration time:pH 8, temperature 60℃, the vibration time of 80 min. The experiment of reusing of the stripping liquid implied that the stripping rate continuously decreased with the increase of recycling time. It could still achieve a petroleum removal rate of 16.53% aftertwo times.