Surfactant-Based Technologies Applicable to Remediation of Mercury Pollution in the Subsurface

摘要

The extension of surfactant-based technologies for use in remediation of mercuric ion [Hg(II)]-impacted soils and ground-waters was explored.In concept,a target metal ion can be selectively sequestered and mobilized from the subsurface by a ligand solubilized in surfactant solution.The selected ligand,1-decyl-2-thiourea (DTU),was used in this study due to its extremely high selectivity for Hg~(2+) and its compatibility with micellar solubilization.In batch semiequilibrium dialysis studies using a mixture of 0.3 mM DTU and 30 mM cetylpyridinium nitrate (a cationic surfactant),99.8% of applied Hg(II) (0.1 mM) was retained,thus demonstrating the effectiveness of this ligand-surfactant system for separating the mobile contaminant from the waste stream.Isolation of the target metal ion from the complex is desirable to allow for ligand and surfactant reuse.As a function of the ligand type,this can be achieved by precipitation,pH stripping,or ligand-ligand exchange.In theory,for DTU,Hg(II) removal can be done at an elevated pH by formation of a soluble mercury-hydroxide complex,which would pass a secondary ultrafiltration stage,allowing retention and reuse of the ligand-surfactant colloid.While only batch studies were conducted for this feasibility study,the possibility of utilizing flow-through ultrafiltration units coupled with contaminant isolation steps in pump-and-treat field applications is discussed.