Effects Of Washing Petroletm Contaminated Soil With Surfactants And Sodium Salts Added Strengthening Effects

At present, more and more different levels of petroleum hydrocarbons contaminated soilhappened by the rapid development of petrochemical and oil products widely used. Specially, thewidespread use of diesel oil and kerosene, pollute the soil. It is bad for areas functiontransformation, secondary utilization of obstacle. This problem catches the attention of thecountries all over the world. Research on the kerosene and diesel oil contaminated soil isparticularly significant, which ensures healthy development of national ecological environmentsecurity, economy and safeguard human health is of great significance.The effectiveness of five kinds of surfactants, such as SDS, SDBS, saponin, Brij35, TX-100,on washing middle level diesel oil contaminated soil was studied. By investigating volatilizationof diesel oil after being mixed with soil, it was found that the mix-time affected the elutionpercentage. It is effective to raise the concentration of surfactants when washing the newcontaminated soil, but not the old. The result shows that the oil-content affects the elutionpercentage, too. When the oil-content reached a point, the elution percentage raises suddenly.Under the concentration of the same multiples of CMC washing, different kinds of surfactantsrank as SDS>SDBS>TX-100>saponin>Brij35.Besides investing the effects of pH, temperature,contaminated-time, agitation time and auxiliaries, measuring contact angle variations ofcontaminated soil before and after washing and zeta potentials were conducted to discuss thechanges of the hydrophilicity of soil particle, interaction of surfactants and soil particles andcleaning-up mechanisms. It was found that the diesel oil removal of20d-old contaminated soil canbe improved by increasing washing temperature or addition of H2O2.The removal of diesel oilreached75%by washing with saponin and H2O2. The diesel oil removal of130d-old contaminatedsoil increased with increasing agitation time of washing. The removal of diesel oil reached65% with SDS at optimal pH of8～10.There are some differences between SDS and SDBS. Afterwashing, the hydrophilicity of the soil can be improved. The soil particles and surfactants arenegatively charged, which can prevent the one more time pollution. These results are valuable tothe application of soil washing to the remediation of diesel oil contaminated soil.The impact of sodium salt on kerosene contaminated soil washing with surfactants wasinvestigated. The result indicated that sodium silicate greatly enhanced the washing efficiency onkerosene contaminated with TX-100. No significant differences were observed between differentsodium salts. Sodium salt of humic acid and sodium silicate had similar enhancement on kerosenecontaminated soil washing with saponin. Sodium humate can be a better choice since itsapplication can also improve soil quality. The enhancement of sodium silicate on kerosenecontaminated soil washing with Tw-80increased with the increase of Tw-80dosage. However,the impact of sodium chloride and sodium tartrate was opposite to sodium silicate. Sodium saltscan reduce surface tension and critical micelle concentration of ionic surfactants to enhance thewashing. Sodium salts can also reduce re-adsorption of oil to soil with nonionic surfactants toenhance the washing. Kerosene contamination can increase the cantact angle of soil, whichindicated the increase of hydrophilicity of soil. Washing with surfactants can reduce thehydrophilicity of soil according to contact angle measurement, which indicated that kerosenecontaminated soil remediation with surfactant can also benefit nutrient and water transportation inthe kerosene contaminated soil.