Dissolution And Transfer Mechanism Of Multi-Components Non-Aqueous Phase Organic Liquids In Saturated Porous Media

With the speeding up of industrialization process, the organic matter of the underground environment pollution has become a global problem. A large-scale and persistent pollutant source will be formed when the non-aqueous phase liquids(NAPLs) contaminants are released into the underground environment by dissolving. In respect of NAPLs pollution control, lots of remediation technologies, such as surfactant flushing, achieve the purpose of the dilution and removal of organic matter by dissolving process, thus dissolving process often is the key to NAPL underground migration of environmental pollution. So far, NAPL dissolution and mass transfer mechanism in underground environment have been not thoroughly understood. Therefore this work mainly studied on NAPL dissolution and mass transfer in saturated porous media to provide theoretical guidance for pollution prevention.In this paper, the determination of NAPL dissolving process related parameters include medium permeability and adsorption. The results showed the smaller media size corresponds with the smaller permeability coefficient; quartz sand of MTBE adsorption type conforms to the linear equilibrium adsorption and the Freundlich balance adsorption, and the media size is smaller, the adsorption ability is stronger.Home-made one-dimensional soil column had been used to study the kinetics of MTBE dissolution, the results showed that the increase of water phase velocity could promote the dissolution of MTBE; The greater initial saturation led to the lower initial dissolved MTBE concentration and the longer time for complete dissolution; the smaller media size can form more small size NAPL so as to promote the dissolution of MTBE. Further, by observing the associated dissolution kinetics of expression, when the saturation was less than 0.3000, media size and NAPL saturation significantly affected the MTBE dissolution, and the saturation of 0.3000 < Sn < 0.5482, aqueous phase velocity played a major role on dissolving process. For multicomponent NAPL dissolution experiment, the low solubility of p-xylene and trichloroethylene had a promoting effect on the dissolution of MTBE. However the coexistence of MTBE and great solubility of ethanol is a dissolution process of competition.Finally, a two-dimension laboratory scale sandbox was manufactured to explore the effect of different parameters on MTBE dissolution under the condition of twodimensional. The results showed that the outlet dissolution process for two-dimensional sand box was approximate to one-dimensional experiment results. However, the sample connection MTBE dissolution concentration which characterizes instantaneous dynamic dissolution process in NAPL source zone was different from outlet dissolution with the significant difference that high initial saturation corresponds to the greater dissolved concentration. Different solution on MTBE dissolution indicated that Tween 80 and ethanol could promote MTBE dissolution; SDBS of below Critical Micelle Concentration(CMC) prolonged the time for complete dissolution of MTBE without enhancement of MTBE mobility. Moreover, it could be deduced that before 80% MTBE was dissolved, the descending order for enhancement effect of MTBE dissolution was as followed: nonionic surfactant Tween 80>cosolvent ethanol>water>anionic surfactant SDBS.