This Special Issue focuses on the development of low-cost nanoadsorbents by sustainably transforming agro-waste and industrial residues into value-added nanomaterials, aligning with circular economy principles. The issue aims to highlight innovative synthesis routes, detailed physicochemical characterization, and the application-driven performance of these materials in environmental remediation, particularly in water purification and pollutant removal. Emphasis is placed on scalability, cost-effectiveness, and environmental impact. Core article types include original research articles presenting novel synthesis strategies and application studies, comprehensive review articles summarizing recent advances and future directions, and short communications reporting emerging techniques or preliminary findings. This collection seeks to bridge the gap between waste valorization and advanced nanomaterial applications, promoting sustainable and economically viable solutions.