Reprocessing of spent nuclear fuel for the recovery of the fi ssionable materials (mainly uranium and plutonium), is performed by solvent extraction. Thermal oxide reprocessing (THORP) is the most widely used technique in which processing fl uids gradually degrade and form stable emulsions that are referred to as interfacial crud (IFC). IFC is highly viscous and stable and its deposition in the nuclear reprocessing circuit results in blockages and plant shutdown for the recovery of IFC and cleaning of the lines. IFC is also encountered in other non-nuclear extraction processes such as crude oil production from oil wells due to the presence of naturally occurring surface active species in crude oil. In this study, we fi rst investigated the synthesis of a non-radioactive IFC simulants and subsequently examined its demulsifi cation behavior (separation into oil and aqueous components). It was concluded that the IFC is stabilized by surface active species, the removal of which results in the demulsifi cation and subsequent phase separation and the prevention of the IFC re-formation. Demulsifi cation was carried out using sulfonated, microporous, crossed-linked materials known as PolyHIPE Polymers (PHP). Demulsifi cation characteristic of the hydrophilic PHP is unique compared with other demulsifi ers, since the capture of surface active species is largely irreversible and hence, demulsifi ed IFC does not reform upon mixing of the oil and aqueous phases. It is therefore possible to remove surface active species from the reaction circuit continuously.
Several techniques, in which different homogenous catalysts and procedures, that are in use for transesterification of a vegetable oil or an animal fat have been successful in synthesizing biodiesel, although with some certain limitations. For such a purpose, among the catalysts employed are acidic as well as basic catalysts. It has been found that acidic catalysts can be tolerant with a high content of free fatty acids found in those low value feedstock oils/fats to be transesterified, although some sort of pretreatment by means of esterification might be required in order to synthesize biodiesel. Moreover, with employing homogenous acidic catalysts, it seems that biodiesel purification procedures are simplified; thus, reducing synthesis cost. In fact, these features of homogenous acidic catalysts render them advantageous over basic ones. With basic homogenous catalysts this; however, has not been possible due to the development of saponification reaction. To effectively perform, such catalysts require that the content of free fatty acids in the feedstock oil/fat is minimal. This requirement is also applicable to the moisture level in the feedstock. In terms of corrosive effects; nevertheless, acidic catalysts are disadvantageous compared to basic ones.
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