Response surface methodology for the optimization of acid dye adsorption onto activated carbon prepared from wild date stones

Abstract

Abstract In the present study, wild date stones (WDS) were used as a novel and sustainable precursor for high-quality activated carbon preparation to be applied for the removal of Acid Blue 25 dye (AB25) from synthetic water. The carbonization temperature of the raw material was selected at 850 °C on the basis of thermo-gravimetric analysis. The adsorbents were characterized by the BET method, Fourier transform infrared spectroscopy, and scanning electron microscopy. The results indicated that the activated carbon presents a high specific surface area (610.84 m2 g−1) and a pore volume (0.224 cm3 g−1) compared with the natural material. Based on the central composite design, the effect of different parameters such as the biomass dose, initial dye concentration, contact time and temperature was optimized and the optimal removal of AB25 (99.61%) was achieved for AB25 concentration of 100 mg L−1 and an adsorbent dose of 0.8 g L−1, at 45 °C after 120 min. The kinetic studies indicated that the pseudo-second-order model was appropriately applied for the adsorption kinetic of AB25 onto wild date stones activated carbon. The intraparticle diffusion model is not the only controlling step, and other mechanisms may be involved in the adsorption process. The Langmuir isotherm provided the best fit with a high correlation coefficient (R 2) of 0.993 and a maximum monolayer adsorption capacity of 181.59 mg g−1.

Keywords

• Activated carbon
• Acid blue 25
• Central composite design
• Adsorption