Adsorption of methylene blue on nano-crystal cellulose of oil palm trunk: kinetic and thermodynamic studies

The adsorption kinetic study of methylene blue using nano-crystal cellulose made from oil palm trunk was investigated. A sample of 0.08 g of nano-crystal cellulose was used to adsorb 300 mL of methylene blue solution, with a varied stirring speed at 100, 200, and 300 rpm. Meanwhile, the concentration of methylene blue was varied at 1, 2, and 3 mg/L. The experimental results showed that the range of adsorption rate constant was 0.0007–0.0130 m/min. For the thermodynamic study, adsorption temperature was varied at 303, 308, 313, and 318 K. The adsorption capacity values for such temperatures were 10.3389, 10.3802, 10.3614, and 10.3464 mg/g, respectively. It was found that ΔH° value of 0.00742 kJ/mol, ΔS° of 0.7758 kJ/mol K and ΔG° value of −242.81 kJ/mol. Based on the curve-fitting using the Henry, Langmuir, and Freundlich isotherm models, this adsorption tended to the Langmuir isotherm model, where the adsorption formed a monolayer covering the surface of the adsorbent. It was also found that the Langmuir affinity constant (KL) value was 4.560 L/mg, and the maximum adsorption capacity (qm) was 8.590 mg/g.