An Investigation of the destruction of ion exchange resins

Ion exchange resins are used for many purposes in various areas of science and commerce. One example is the use of cation exchange resins in the nuclear industry for the clean up of radioactively contaminated water (for example the removal of 137Cs). However, during removal of radionuclides, the resin itself becomes radioactively contaminated, and must be treated as Intermediate Level Waste. This radioactive contamination of the resin creates a disposal problem. Conventionally, there are two main avenues of disposal for industrial wastes, landfill burial or incineration. However, these are regarded as inappropriate for the disposal of the cation exchange resin involved in this project. Thus, a method involving the use of Fenton's Reagent (Hydrogen Peroxide/soluble Iron catalyst) to destroy the resin by wet oxidation has been developed. This process converts 95% of the solid resin to gaseous CO2, thus greatly reducing the volume of radioactive waste that has to be disposed of. However, hydrogen peroxide is an expensive reagent, and is a major component of the cost of any potential plant for the destruction of ion exchange resin. The aim of my project has been to discover a way of improving the efficiency of the destruction of the resin thus reducing the cost involved in the use of hydrogen peroxide. The work on this problem has been concentrated in two main areas:-1) Use of analytical techniques such as NMR and IR to follow the process of the hydrogen peroxide destruction of both resin beads and model systems such as water soluble calixarenes. 2) Use of various physical and chemical techniques in an attempt to improve the overall efficiency of hydrogen peroxide utilization. Examples of these techniques include UV irradiation, both with and without a photocatalyst, oxygen carrying molecules and various stirring regimes

The occurrence of obtuse junction angles and changes in channel width below tributaries along the Mekong River, South-East Asia

Classic descriptions of drainage patterns suggest that confluence angle is determined by the shape of the drainage basin unless constraining factors, such as the geological structure, affect stream flow. Downstream changes in channel width below tributary junctions have long been associated with tributary inputs of flow and sediment. Analysis of tributary junction geometry and channel width changes in large rivers and over large reaches is sparse. The Lower Mekong Basin exhibits a generally dendritic drainage network despite flowing through a diverse array of geological settings. Publicly available SPOT?5 imagery from Google Earth was used to identify and catalogue junction geometries and downstream changes in channel width below tributary junctions along a ~2200 km reach of the Mekong River. Of the 284 junctions identified, the majority (66.2%) were acute. However 12 (4.8%) were found to be normal (90°) and 75 (30%) were found to be obtuse. This latter number is in contrast to previous studies over similar spatial scales which found little evidence of obtuse junctions. Meander extension of the incoming tributary and deflection of the tributary across bedrock shoulders were found to be the dominant geomorphological causes of obtuse tributary junctions. The relationship between the width of the tributary channels and the width of the mainstem upstream and downstream of the confluences was analysed. It was observed that, over the whole reach, a slight narrowing occurred immediately below tributary junctions. Although the changes themselves were small, the slight net narrowing is shown to be statistically significant. The observed relationship is shown to vary considerably with geology. The geological control suggests that complex factors play important roles in determining changes to channel width across large systems and that simple cause–effect relationships do not hold in such complicated geological settings