The escalating crisis of anthropogenic water contamination necessitates the development of advanced, sustainable, and economically viable remediation technologies. This chapter provides a comprehensive and critical examination of carbon-based materials as a superior class of adsorbents, contextualized within the overarching principles of ecomaterials. The material landscape is traversed from traditional activated carbons to state-of-the-art nanostructures, including graphene and carbon nanotubes, with significant focus placed on biochar and hydrochar, which epitomize the waste-valorization paradigm. The discussion meticulously explores the rational design and synthesis strategies employed to engineer tailored physicochemical properties—high specific surface area, hierarchical porosity, and specific surface functionalities—for targeted contaminant sequestration. The intricate interfacial mechanisms governing adsorption are elucidated, critically analyzing the synergistic interplay between physisorption (e.g., van der Waals forces, π–π interactions) and chemisorption (e.g., electrostatic attraction, surface complexation). Furthermore, the chapter assesses the extensive applications of these materials for the remediation of a wide spectrum of pollutants, from legacy heavy metals and organic dyes to recalcitrant emerging contaminants. Crucially, the sustainability of these systems is evaluated through an in-depth analysis of regeneration methodologies, sustainable end-of-life scenarios, and overarching life cycle considerations. By bridging fundamental materials science with pragmatic environmental engineering, this work identifies the remaining challenges and charts the future research trajectory towards the next generation of multi-functional carbon ecomaterials for ensuring global water security.