胶态泡沫在饱和介质迁移特性及对PCE冲洗效果

Migration characteristics of colloidal gas aphron in saturated media and flushing effect on PCE

利用表面活性剂胶态微泡沫冲洗技术来提高四氯乙烯(PCE)在地下水的溶解性和流动性,提高污染物迁移通量,强化去除效果.主要工艺参数和影响因素对泡沫稳定性的影响,结果表明4000r/min的搅拌转数即可产生稳定的胶态微泡沫,泡沫稳定性随表面活性剂浓度增大有小幅度提高,PCE对泡沫稳定性有不利影响;胶态微泡沫在含水层的迁移规律表明,泡沫前端迁移时不断破裂并气液分离,形成气体在上部,液体在下部,后续泡沫稳定向前推流的迁移模式,泡沫在含水层中受到地下水的静水压力,与在土壤迁移相比其体系压力更大,泡沫破裂更严重、迁移速率更慢;和液体冲洗相比,泡沫冲洗对PCE增溶增流效果明显,介质粒径为0.1~0.25mm、0.25~0.5mm和0.5~1mm时,PCE去除率分别达到83.7%、90.8%和98.2%,介质粒径越大,去除效果越明显.

Tetrachloroethylene(PCE)is one of the commonly found organic pollutants in groundwater.After entering and accumulating in aquifer,the pollutant is difficult to dissolve,move and desorb from media,resulting in incomplete repair,rebound effects and some other remedial problems.In this study,surfactant colloidal gas aphron(CGA)flushing technology was used to increase the solubility and the mobility of PCE in aquifer,by which the transport flux of the pollutant could be increased and the remedial effect could be enhanced.The main parameters and influencing factors on CGA stability showed that the stirring speed of 4000r/min could produce stable CGA.The stability increased slightly with the increase of surfactant concentration,and PCE had an adverse effect on it.Besides,the migration of CGA in aquifer showed that the migration front of foam burst continuously during the migration process,causing the separation of the gas and the liquid in the front migration part.The gas migrated in the upper part with the liquid in the lower part in the front area of foam,and the subsequent stable foam pushed them forward.The pressure on foam in aquifer was greater than that in soil,resulting in the foam bursted more severely and the rate of migration got slower.In addition,compared with liquid,the flushing of foam had better effects on enhancing the solubility and mobility of PCE.When the media sizes were 0.1~0.25mm,0.25~0.5mm and 0.5~1mm,the corresponding removal rate of PCE was 83.7%,90.8%and 98.2%respectively,and the larger the media sizes,the more obvious the removal effect.