Utilization of citric acid-modified chitosan derived from oyster shells for the adsorptive removal of cadmium ions from wastewater
Akanbi Magdalene Nkeiru
Department of Polymer Engineering, Federal University of Technology Owerri, Nigeria
Ejidike Lynda Chinyere
Department of Chemistry, Nnamdi Azikiwe University, Awka, Nigeria
Eze Patricia Nnebuogo
Department of Chemistry, Federal College of Education (Technical) Asaba, Nigeria
Okore Glory Jerry
Department of chemistry, Alvan Ikoku Federal University of Education, Owerri, Nigeria
Aharanwa Bibiana Chimezie
Department of Polymer Engineering, Federal University of Technology, Owerri, Nigeria
Oze Nwanneamaka Rita
Department of Chemistry, Federal University of Technology, Owerri, Nigeria
DOI: https://doi.org/10.59429/ersr.v2i2.10985
Keywords: Wastewater treatment; adsorption studies; kinetics; crustaceans shells; cadmium metal
Abstract
The increasing contamination of water bodies by heavy metals, particularly cadmium (Cd²⁺), poses a significant threat to environmental and public health due to its toxicity, persistence, and bioaccumulate nature. This study investigates the potential of citric acid-modified chitosan, derived from oyster shells, as an eco-friendly and cost-effective adsorbent for the removal of cadmium ions from aqueous solutions. Chitosan was extracted through deproteination, demineralization, and deacetylation processes, followed by chemical modification using citric acid to enhance its adsorption properties. Characterization of the modified chitosan was conducted using Fourier Transform Infrared Spectroscopy (FTIR), UV–Visible Spectroscopy (UV–Vis), and Atomic Absorption Spectrophotometry (AAS). FTIR analysis confirmed the successful transformation of oyster shell into chitosan, with the emergence of functional groups such as hydroxyl, carbonyl, and amine groups critical for metal ion binding. UV–Vis. spectroscopy revealed strong absorbance in the UV region and optical transparency in the visible range, indicating high purity and suitability for biomedical and environmental applications. Batch adsorption experiments were performed to evaluate the effects of initial cadmium concentration, contact time, and temperature. The results showed that maximum adsorption occurred at low concentrations, with equilibrium reached at 60 minutes and optimal performance at 40°C. Isotherm modeling revealed that the Freundlich model (R² = 0.8389) better described the adsorption behavior than the Langmuir model (R² = 0.0245), suggesting multilayer adsorption on a heterogeneous surface. Kinetic studies indicated that the pseudo-second-order model (R² = 0.9738) best fit the data, implying chemisorption as the dominant mechanism. Overall, the study demonstrates that citric acid-modified chitosan is a promising biosorbent for cadmium removal, offering a sustainable solution for wastewater treatment. Further optimization and real-world application studies are recommended to enhance its practical viability.
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