Co-precipitation fabrication of cellulose/chitosan-aniline grafted composites for efficient removal of Pb2+ ions from aqueous solution.

Heavy metal ions, are non-biodegradable, high toxic tendency, and have serious hazardous effects on the health of humans. Then, removing them from the environment using different techniques is necessary. Several routes are expensive, low-efficient, and require a long time to achieve adsorption equilibrium. In this paper, novel chitosan-based composites CS/CL@An-1 and CS/CL@An-2 were synthesized, characterized by FT-IR, DSC, XRD, and SEM, and applied as new adsorbents in batch experiments for the removal of Pb2+ ions from aqueous solution. The effect of important parameters such as initial pH solution (2-7), adsorbent dose (0.005, 0.01, and 0.02 g), adsorption contact time (0-240 min), initial Pb2+ metal ion (25-200 mg/L) and ionic strength on their adsorption behavior was investigated. The adsorption results at best conditions (pH solution = 6, adsorbent dose = 0.02 g, contact time = 180 min and initial ion concentration = 100 mg/L) predicted that the maximum removal percentage (adsorption capacity) of Pb2+ metal ion using CS/CL@An-1 and CS/CL@An-2 is 95.6 % (239 mg/g) and 98.8 % (247 mg/g), respectively, much higher than other chitosan-based adsorbents. The absorption kinetic results confirmed that the adsorption of Pb2+ showed the best fit with the pseudo-second-order (PSO) model as a chemisorption process. The absorption mechanism was regulated by the coordination and n-π attractions of Pb2+ ions with the active sites on the surface of adsorbents. The adsorption of Pb2+ was well-fitted by a homogeneous monolayer Langmuir isotherm model. Finally, the reusability of adsorbents was examined after five adsorption-desorption cycles, and the results show that the adsorption efficiency still reaches >90 %. Therefore, the compounds were potentially new adsorbents for removing Pb2+ ions from aqueous solution.