Sustainable Bio-Based Polymer Adsorbents for Water Remediation: A Systematic Review of Functionalization Strategies, Performance Enhancement, and Circular Economy Integration

Global water scarcity affects over 57% of the world’s population, with industrial effluents discharging more than 200,000 tons of synthetic dyes and substantial heavy metal quantities annually. Conventional treatment methods remain energy-intensive and generate secondary toxic sludge, necessitating sustainable alternatives aligned with circular economy principles. This systematic review, conducted following PRISMA 2020 guidelines, analyzes 4626 studies from the Scopus database (2010–2026) using bibliometric analysis (RStudio/bibliometrix), network visualization (VOSviewer), and interactive graphics (Plotly). The field exhibits exponential growth (R0 = 96.5%, R2 = 91.1%), with publications concentrated in Materials Science (16%), Environmental Science (15%), and Chemistry (14%). Cellulose- and chitosan-based adsorbents demonstrate exceptional capacities: 1604 mg/g for mercury (thiolated chitosan) and 2100 mg/g for Congo red (cationic nanocellulose). A critical knowledge gap remains the limited integration of underutilized biomass with synthetic polymers such as PVDF—addressed in only 5 publications—despite hybrid systems achieving 92% circular readiness and 95% resource recovery. Combined experimental and computational approaches enhance adsorption performance by 20–50%, with materials retaining over 80% reusability after 10 cycles. Compared with conventional technologies, bio-based alternatives reduce energy consumption by 40% and CO2 emissions by 55% (0.043 kg CO2e/m3), while transforming agro-industrial wastes into high-performance adsorbents. These findings position functionalized bio-based polymers as technically, economically, and environmentally superior options for advanced water remediation, contributing to sustainable wastewater treatment and resource recovery within circular economy frameworks.