Perfluoroalkyl substances (PFASs) are recalcitrant contaminants of emerging concern that have widespread distribution in water sources, and exhibit potential to persist and bioaccumulate. Non-destructive and destructive remediation strategies have been actively investigated to remove PFAS. Adsorption on activated carbon is the most widely used non-destructive treatment method to remove PFAS. However, limited innovation has occurred in the field of activated carbon materials and there is a need to develop ultra-high surface area activated materials that exhibit high adsorption capacity and selectivity for target contaminants. Furthermore, non-destructive methods only transfer the contamination from one phase to another and therefore must be used in conjunction with destructive treatment methods to effectively remove and mineralize the target contaminant. In recent years, there has been growing interest to use Advanced Oxidation Processes (AOPs) to degrade PFAS. However, progress in the field has been hampered by the ambiguity that exists regarding the role of two key reactive oxygen species (ROS) i.e. hydroxyl radical (•OH) and superoxide radical anion (O2•-) in degrading PFAS with some studies demonstrating their effectiveness while others claiming the contrary. This dissertation aims to provide mechanistic insights into the treatment of PFAS and other contaminants of emerging concern by: i) Developing fundamental understanding of how the structure of a novel ultra-high surface area activated carbon relates to its function as an adsorbent. ii) Resolving the ambiguity regarding the role of •OH and O2•- in degrading PFAS.