The Adsorption Performance of Chitosan Derived from Waste Lobster Shells on Aluminum (Al3+), Nickel (Ni2+), and Lead (Pb2+)

Abstract This study investigates the adsorption behavior of chitosan derived from waste lobster shells toward aqueous systems containing aluminum (Al 3+ ), nickel (Ni 2+ ), and lead (Pb 2+ ), and evaluates the removal behavior using isotherm and kinetic modeling approaches. Chitosan production yield was determined gravimetrically, and material characterization was confirmed through Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Batch experiments were conducted using aqueous solutions prepared at initial concentrations of 30, 50, and 70 ppm within a pH range of 4.5–5.0, at 25 °C. Solution-phase changes during adsorption experiments were monitored using UV–Vis spectrophotometry under controlled single-metal conditions. The obtained adsorption capacities, therefore, represent apparent adsorption capacities based on spectrophotometrically monitored concentration changes, allowing comparative evaluation of removal behavior. Isotherm modeling showed that the Langmuir model provided the best fit to the experimental data, suggesting removal behavior consistent with monolayer-type adsorption assumptions. The Al 3+ system exhibited the highest apparent adsorption capacity (125 mg/g), followed by Ni 2+ (46.51 mg/g) and Pb 2+ (49.26 mg/g). Kinetic analysis indicated that the pseudo-second-order model best described the uptake behavior under the studied conditions. These findings demonstrate that lobster-shell-derived chitosan exhibits strong comparative removal performance in metal-containing aqueous systems, particularly in the Al 3+ system, under controlled laboratory conditions.