Adsorption behavior and techno-economic analysis of citric acid-modified chitosan for heavy metal removal from wastewater

Citric acid-modified chitosan was synthesized with the citric acid precursor. The findings indicated that the modification of chitosan enhanced surface-active sites, stability in acidic systems, and surface area. Together this improved multi-heavy metal sorption and facilitated the reuse of exhausted sorbent. The findings revealed that the sorbent demonstrated outstanding sorption capabilities for iron, copper, and lead ions, and its maximum adsorption capacities were 8.18, 86.21, and 312.5 mg g⁻¹ for Pb, Fe, and Cu, respectively. The Pb ions with greater nuclear radii than the Cu and Fe ions may get comparatively desorbed. This is due to the competitive adsorption phenomena. Henceforth, the adsorption capacity of the Cu ions has been comparatively higher than the Pb ions in the considered mixed metal ion solution. For Cu, Fe, and Pb, the medium Cit-CS resin exhibited significant desorptive efficacies of 78.69 %, 75.31 %, and 69.63 % respectively. The lab-scale conceptual synthesis costs of the resins were 1204.05, 1260.21, and 1361.27 INR per 10 g of low Cit-CS, medium Cit-CS, and high Cit-CS, respectively. For industrial-scale manufacturing, the resin costs are 627.18, 649.64, and 690.07 INR per 10 g of low Cit-CS, medium Cit-CS, and high Cit-CS, respectively. Additionally, for medium Cit-CS, % contribution of chitosan, equipment, manpower, electricity, and other chemicals costs was 58.48, 3.21, 12.70, 3.35 and 22.26 % respectively for the lab-scale manufacturing case and the corresponding costs for the industrial scale case were 45.38, 6.22, 24.63, 6.49 and 17.28 % respectively.