This review provides a comprehensive analysis of organically grafted clay minerals modified with organo-alkoxides, silanes, and amine-based compounds for water treatment applications. Emphasis is placed on per- and polyfluoroalkyl substances (PFAS) as representative emerging contaminants due to their persistence and environmental relevance. The review systematically examines synthesis strategies, surface functionalization mechanisms, and structure–performance relationships governing adsorption behavior. The analysis demonstrates that adsorption performance is controlled by the interplay between grafting chemistry, surface accessibility, and environmental conditions rather than adsorption capacity alone. While ion-exchange organoclays exhibit high adsorption capacities under controlled conditions, covalently grafted and polymer-modified systems provide superior stability and resistance to leaching. However, discrepancies in experimental conditions across studies limit direct comparison of reported adsorption capacities. The review identifies key challenges related to regeneration efficiency, environmental safety, and scalability, and highlights that long-term stability and compatibility with realistic water matrices are decisive factors for practical implementation. Future research should focus on standardized testing protocols, pilot-scale validation, and comprehensive environmental risk assessment.