| Summary: | The human hair has been wasted in many parts of the world and even considered useless, however human hair is a great source of keratin. Keratin represents an important renewable biomaterial which could be further explored. The number of applications is vast and due to its potential, the dissolution of human hair was further investigated in this Thesis.
It has been demonstrated that ionic liquids have the ability to dissolve cellulose and other keratin sources, such as feathers and wool. For this reason, the dissolution of human hair with ionic liquids was investigated in this study. Imidazolium and pyrrolidinium based ionic liquids were studied, and the impact of the cation on dissolution was found to be marginal. Conversely, the anion plays an important role disrupting the hydrogen and disulfide bonds, which leads to the dissolution of hair. This is due to nucleophilic anions such as acetate, dimethylphosphate or chloride. Increasing the aliphatic chain length of the cation was also shown to have an impact on the dissolution of hair due to the increase of the viscosity of the ionic liquid. The efficiency of the dissolution process was also considered, where dissolution assisted by microwave radiation proved to be faster than conventional heating.
It was found that keratin, extracted from waste biomass, has many applications, and as such, it was investigated whether it was possible to extract keratin material from the dissolution of hair. Recovery of keratin material was possible using [C2C1Im][OAc] and [C2C1Im][Me2PO4]. The recovery of keratin material was further analysed in order to investigate its chemical characterisation. In terms of efficiency, greater amounts of keratin material was recoverable from the dissolution with [C2C1Im][Me2PO4] than [C2C1Im][OAc]. This may be related to the higher affinity of the dissolved particles to the ionic liquid phase which makes the regeneration process challenging.
Since the dissolution of hair was possible with ionic liquids, the ability ionic liquids to modify the structure of hair in specific bonds was investigated. These modifications were then investigated by infrared spectroscopy. During this investigation a deeper analysis was conducted to understand the natural structure of hair and how to identify possible modifications in its structure by infrared spectroscopy.
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