Chitosan-Vanillin Polymers from Farfantepenaeus Duorarum Residues for Lead Ion Removal from Aqueous Solutions

Water contamination by lead has been studied extensively due to the risks it can cause for humans and the environment. Although there are traditional methods for removing this contaminant, it is necessary to evaluate sustainable and ecological alternatives such as chitosan obtained from shrimp waste. Chitosan and vanillin-functionalized chitosan were synthesized from shrimp (Farfantepenaeus duorarum) residues and evaluated for their ability to remove lead ions from aqueous solutions. The polymers were characterized using Fourier Transform InfraRed (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). FT-IR analysis confirmed the presence of characteristic functional groups, including the amino group at 1630 cm-1 and the C=O stretch at 1654 cm-1. SEM images revealed a smooth surface for pure chitosan, while functionalized chitosan exhibited a rougher surface with cracks, indicating increased adsorption sites. XRD analysis showed a reduction in crystallinity for functionalized chitosan, with peaks at 2θ=20° decreasing in intensity. Adsorption mechanisms were studied using the Langmuir and the Freundlich isotherms. The maximum adsorption capacity is accomplished at pH = 5 with an equilibrium concentration of 2 g/L for both polymers. The Langmuir isotherm best fit the experimental data for pure chitosan, with a maximum adsorption capacity of 1.9121 mg/g, while the Freundlich isotherm was more suitable for functionalized chitosan, with a maximum adsorption capacity of 2.6049 mg/g. The results suggest that chitosan and vanillin-chitosan polymers derived from shrimp residues are effective and environmentally friendly adsorbents for lead ion removal from aqueous solutions.