Chemical precipitation is frequently used in heavy metal removal; it involves the addition of aluminium (III) salts followed by an increase in pH to produce an insoluble hydrous oxide precipitate (floc), which is then easily separable. However, the hydrous oxides are not 100% effective at removing heavy metal contaminants from water at pH 7 and the addition of polymers bearing chelating groups can significantly enhance the adsorption of metals by floes. Silicon polymers bearing chelating groups were designed and synthesized for the enhanced removal of heavy metals from wastewater by floes. A number of synthetic strategies were exploited in the synthesis of these silicone polymers, involving the modification of silanes, cyclic siloxanes and silicone polymers containing vinyl-, halogeno-, hydrido, amino- and mercapto- functionalities. Investigations into the effect of the silicone polymers on the individual adsorption of cadmium, cobalt, manganese and nickel, as well as the simultaneous adsorption of eight heavy metal contaminants by aluminium flocs were performed. Adsorption, studies have shown that the presence of silicone polymers can enhance the removal of these heavy metal ions by aluminium floes to varying extents up to 98%, even when in competition with other heavy metal ions. Cadmium adsorption was greatly enhanced in the presence of a wide range of silicone polymers containing a mixture of functional groups and can be accounted by the fact that it does not show a preference for a particular geometry and can form complexes with oxygen, nitrogen and sulfur donor ligands. The adsorption of manganese, cobalt and nickel was only enhanced in the prescence of certain silicone polymers, depending on the properties of the metal ions and silicone polymer. The results show that the efficiency of the polyelectrolytes in enhancing heavy metal removal depends on the number and type of chelating groups present on the silicone polymer.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:485024 |
| Date | January 2008 |
| Creators | McGrandle, Sarah Jane |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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