| Popis: |
Experiments were performed to study the effect of oxidation on organic phase binding of cobalt-60 in turbine lubricating oil and its subsequent removal. Binding behavior was inferred from measurements of the organic phase cobalt-60 concentration, operationally defined as that remaining following a water wash at 90°C. The effectiveness of each treatment process was based on measurements of cobalt-60 concentrations remaining in the oil following the process. A complete, commercial grade oil containing additives and the base oil without additives were spiked with cobalt-60 and heated in the presence of oxygen. In the base oil, organic phase cobalt-60 concentrations increased monotonically with heating time. In the complete oil, the concentrations increased initially and subsequently declined. The differences in behavior are attributed to antioxidant and antiwear additives in the oil which bind with metals. Both oils were subjected to a variety of decontamination treatments including filtration, washing, and chelation. For the base oil, the treatments were generally less effective for the most highly oxidized samples. In contrast, for the complete oil there were dramatic improvements in treatment for the most highly oxidized samples. It is theorized that the improvement in decontamination for highly oxidized samples is due to the destruction or transformation of the additives responsible for cobalt binding and the formation of oil insoluble polymers that remove it from the oil phase. It is concluded that oxidation might be effectively employed as part of a scheme for decontaminating waste lubricating oils. |
