Sustainable Removal of Metaldehyde Pesticide via Modified Cellulose Adsorbents

In this study, commercial, plant-based, and paper-based cellulose acetate (CCA) was modified to develop an efficient adsorbent for removing metaldehyde (MD) from aqueous solutions. The modified commercial CCA exhibited the best performance and was selected for further characterization using FTIR, EDX, SEM, and XRD. Batch experiments were conducted to assess the effects of parameters such as contact time (10-100 min), initial MD concentration (10-100 mg/L), adsorbent dosage (0.01-0.12 g), and pH (2-12). Kinetic, isotherm, and thermodynamic analyses were carried out to gain a deeper understanding of the adsorption process. The maximum MD removal observed was 55.34% at an optimal dosage of 0.08 g and room temperature (25°C). The experimental data were best fitted by the pseudo-second-order and power function models, with correlation coefficients of 0.9947 and 0.9917, respectively. Among the isotherm models tested, including Langmuir, Freundlich, Temkin, Jovanovich, and Harkins-Jura, the Freundlich model provided the best fit for equilibrium data (R² = 0.995), indicating that the adsorption occurred in a heterogeneous environment. The maximum adsorption capacity was 2.21 mg/g. Thermodynamic analysis revealed that the adsorption process was exothermic and spontaneous, with an enthalpy change (ΔH°) of -29.9 kJ/mol, entropy change (ΔS°) of 91.29 J/mol, and Gibbs free energy (ΔG°) values of -7.27, -4.45, and -2.65 kJ/mol at 298, 313, and 328 K, respectively. These findings suggest that CCA could be a promising alternative to activated carbon for adsorbent applications, providing a more energy-efficient solution. Further studies are necessary using other pollutants.