Bio-based chitosan-grafted microcrystalline cellulose as an adsorbent for efficient removal of chromium and cadmium from simulated wastewater

Heavy metals such as Chromium (Cr) and Cadmium (Cd) are highly toxic elements detected in industrial wastewater. In this work, a bio-based composite adsorbent composed of chitosan (M) and CS-grafted microcrystalline cellulose (MCC) is utilized for the removal of Cr and Cd from simulated wastewater. CS, MCC, CS grafted MCC (CS-g-MCC), and the CS/CS-g-MCC composite were prepared and inspected using Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Wide-angle X-ray diffraction (WAXD) analysis. Metal concentrations before and after adsorption by the CS/CS-g-MCC composite were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES), and removal efficiencies for total chromium and cadmium were reported. Batch adsorption experiments were conducted to examine the effects of pH, contact time, adsorbent dosage, and initial metal concentration. The adsorption kinetics were adequately described by the pseudo-second-order model, indicating that chemisorption may contribute to the uptake process. Equilibrium data were analyzed using Langmuir and Freundlich isotherm models to provide comparative insight into adsorption behavior, yielding estimated maximum capacities of approximately 46 mg/g for Cr Total and 74 mg/g for Cd²⁺ under the tested conditions. Interference studies showed that PO₄³⁻ significantly suppressed Cr Total uptake, while Cd²⁺ adsorption was less affected by competing ions. Regeneration experiments over four adsorption–desorption cycles using (NH₄)₂SO₄ demonstrated reasonable short-term reusability, although gradual performance decline was observed. Overall, the CS/CS-g-MCC composite shows promise as a bio-based adsorbent for heavy-metal removal, while further studies are required to strengthen equilibrium modeling and long-term stability assessment. • Bio-based CS/CS-g-MCC composite synthesized from CS and MCC. • Efficient removal of anionic Cr and cationic Cd under optimized conditions. • Maximum adsorption capacities of 46 mg/g (Cr) and 74 mg/g (Cd) were achieved. • Adsorption kinetics followed the LPSO model, indicating chemisorption. • The Freundlich isotherm suggests surface heterogeneity.