Grafted Chitosan for Dye Removal: Synthesis Cost, Material Efficiency and Reuse Risk

The economic viability of chitosan-based adsorbents depends on laboratory-scale synthesis costs, adsorption performance, regeneration behavior and synthesis-route complexity. However, these factors are rarely evaluated within a unified framework, limiting informed material selection. Herein, an integrated framework combining activity-based costing and total cost of ownership (ABC−TCO), cost-effectiveness analysis, material-use efficiency and complexity-adjusted risk−return assessment was developed. Four chitosan derivatives, chitosan grafted with acrylic acid (Ch-g-Aa) or acrylamide (Ch-g-Aam) in powder and bead forms, were systematically evaluated for Remazol Yellow Gelb 3RS (RY) and Basic Yellow 37 (BY) removal over four consecutive adsorption−desorption cycles. The results revealed that bead formation improved cost-effectiveness for Ch-g-Aa but reduced it for Ch-g-Aam. Notably, the lowest synthesis cost (€14.35 g−1, Ch-g-Aa beads) did not correspond to the lowest synthesis cost per mg of RY removed: Ch-g-Aa beads incurred 2.6 times the cost of Ch-g-Aam powder (0.01085 versus 0.00423 € mg−1). To assess synthesis-route efficiency, complexity-adjusted risk−return analysis demonstrated that Ch-g-Aa beads achieved the highest economic return (39.01%) and return-to-risk ratio (5.02), despite requiring nine synthesis steps versus six for powders. Raw materials consistently dominated synthesis costs (>60% of batch costs for powders), identifying reagent optimization and solvent recovery as key priorities for synthesis optimization. Overall, bead formation provided no universal advantage; its value depended on graft chemistry, synthesis yield and target pollutant. The framework delivers three benefits: it distinguishes synthesis cost from cost-effectiveness, revealing overlooked trade-offs; identifies when additional synthesis complexity is economically justified; and pinpoints cost and material-use hotspots to guide polymeric adsorbent design.