Continued legislative pressure to reduce automotive exhaust emissions requires an automotive catalyst to operate at its peak efficiency up to 120,000 miles. Catalyst life is shortened by the poisoning of active sites by glazing caused by the deposition of phosphorous. The primary source of phosphorous is zinc dialkyldithiophosphate, an antiwear and antioxidant additive in engine oil. Therefore, the reduction of the phosphorous level in engine oils raises concern for increased wear of engine components. In an engine equipped with a direct acting mechanical bucket-type valvetrain, high contact stress coupled with sliding action at the cam and tappet contact makes it particularly vulnerable to wear. Motored single cam lobe valvetrain experiments were conducted to evaluate the wear protection capability of several 0.05 wt% P containing engine oils while the oil is fresh. The wear protection capability of vehicle drain samples was also evaluated to ensure adequate protection up to the point of oil change. It was observed that used oils provided significantly improved wear protection capability coupled with reduced friction. An analysis of the tappet shim surface showed that the composition of lubricant-derived protective films formed with used oils is very different than that formed with fresh oil, which may very well explain improved wear characteristics and reduced friction with used oils.
The extension of surfactant-based technologies for use in remediation of mercuric ion [Hg(ll)]-impacted soils and groundwaters 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 Hg2+ 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(ll) (0.1 mM) was retained, thus demonstrating the effectiveness of this ligandsurfactant 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(ll) 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 ligandsurfactant 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.
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