Feasibility study on the utilization of low-cost sawdust for adsorption of caffeine: equilibrium, optimization, and response surface modeling

The study focuses on the adsorption of caffeine (CAF) from aqueous solutions onto sawdust (SD), a naturally available, eco-friendly, and low-cost adsorbent. The influence of various operating parameters such as; CAF initial concentration (5-20 mg/L), SD dosage (0.5-3.0 g/L), and pH (3.0-9.0) was investigated in detail. The experimental results of the adsorption process showed the maximum CAF removal efficiency of 94.5% at optimized conditions (CAF initial concentration 5 mg/L, SD dosage 2.0 g/L, and pH 7.0). The applicability of adsorption isotherm models for CAF removal by SD has also been revealed. The R-2 values obtained for Langmuir and Freundlich isotherms (0.9371 and 0.9966) showed that the Freundlich isotherm model with the higher R-2 value of 0.9966 had better suitability than the Langmuir isotherm model. The suitability of experimental data was analyzed with response surface methodology using Design-Expert software. The obtained analysis of variance results with a coefficient of determination; R-2 = 0.9643 and adjusted R-2 value = 0.9516 demonstrated good agreement between experimental and predicted data. The 3D surface plots confirm the significance of all the three parameters investigated.

Automated summary

This study investigates the adsorption of caffeine from aqueous solutions using sawdust as a natural, eco-friendly, and low-cost adsorbent. The effects of various operating parameters on the adsorption process were examined in detail. The results indicate that the maximum removal efficiency of caffeine can reach 94.5% under optimized conditions. The suitability of different adsorption isotherm models was also analyzed, and the Freundlich model showed better fit to the experimental data. Additionally, response surface methodology was employed to analyze the experimental data, demonstrating a good agreement between the experimental and predicted results.