Investigation of the Wetting Behavior of Coal Tar in Three Phase Systems and Its Modification by Poloxamine Block Copolymeric Surfactants

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• 作者：Jingfeng Dong ; Babur Chowdhry ; and Stephen Leharne
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：January 15, 2004
• 年：2004
• 卷：38
• 期：2
• 页码：594 - 602
• 全文大小：332K
• 年卷期：v.38,no.2(January 15, 2004)
• ISSN：1520-5851

文摘

The removal of dense nonaqueous phase liquid mixtures(DNAPLs) from rocks and subsurface soils is an ongoingremedial challenge. Very often the wetting preferences ofthe system are not altered by exposure to the DNAPL.However, there are systems where the wetting propertiesof the solid phase have been altered from stronglywater wetting by exposure to the DNAPL. In these casessome technique is necessary for reducing the work ofadhesion between the DNAPL and the mineral surface. Thefocus of this report is the problems posed by coal tar inunconsolidated sands. It is shown that coal tar can alter thewetting properties of quartz, the principal component ofsands, and is thus capable of adhering to the surface. Inthis investigation the ability of several members of thepoloxamine family of polymeric surfactants to aid in theremoval of coal tar from sand was evaluated. The poloxaminesare tetrafunctional block copolymeric surfactants, whichcontain four poly(ethylene oxide)-block-poly(propylene oxide)chains joined to a central ethylenediamine moiety viathe nitrogen atoms. Contact angle measurements of coaltar on a quartz surface immersed in aqueous surfactantsolution and the interfacial tension between coal tar andaqueous surfactant solution have been measured. Coal tar/water interfacial tensions are reduced to values in theregion of 2 mN m^-1 at surfactant concentrations ofapproximately 0.1 w/v %. Poloxamine surfactant impacton the static contact angle is more complex. In some casesthe polymeric surfactants alter the wetting behaviorfrom strongly water wetting to weakly water wetting.However, other poloxamines appear to have little if anyimpact on the contact angle, which remains strongly waterwetting. The foregoing measurements have then beenused to calculate the work of adhesion of the coal tar toquartz and the results qualitatively compared with theconcentration of surfactant solution required to visuallydemonstrate the complete de-adhesion of coal tar to thequartz. It is shown that at surfactant concentrations belowthe critical micelle concentration (cmc) of the surfactant,the work of adhesion can be reduced sufficiently toensure complete removal of coal tar from both quartz andsand.