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.