Activated carbon derived from sugarcane and modified with natural zeolite for efficient adsorption of methylene blue dye: experimentally and theoretically approaches

Abstract

Activated carbon/natural zeolite (AC/NZ) was introduced as an effective and stable adsorbent for the enhancement of the adsorption of methylene blue (MB). The activated carbons (ACs) were prepared from sugarcane waste by calcination at different temperatures from 500 to 900 °C. The samples were characterized for confirming their structure and chemical composition by using many techniques. For activated carbon calcinated at 500 °C (AC500), the XRD patterns showed many broad peaks which confirm the amorphous phase of carbonization with disordered micro-graphite stacking. The SEM images of the AC500/NZ nanocomposite show that the zeolite surface is covert with the AC500 particles. The AC500/NZ nanocomposite showed light absorption capability in the visible region than activated carbon only. Batch experiments were performed to study the influence of various practical variables on adsorption processes. Dye adsorption isotherms and kinetics were also investigated. The effect of contact time, starting MB concentration, and pH were all measured. Adsorption of MB was reached to maximum removal (99.2 %) using 50 mg of AC500/NZ after 45 minutes. About 51 mg/g was found to be the maximum AC500/NZ adsorption capacity for MB dye with an initial concentration of 30 ppm, at 25 °C, pH 7, and an AC500/NZ mass of 50 mg. According to the kinetic tests, the best kinetic model for MB adsorption was pseudo-second-order. The adsorption isotherm of dye onto AC500/NZ almost agreed with the Temkin isotherm model. Adsorbed heat energy B value calculated according to Temkin model was less than 1.0 kcal/mol which indicates that the adsorption reaction of MB onto AC500/NZ occurs physically in the concentration studied. Additionally, the adsorption mechanism was also evaluated using Weber's intra-particle diffusion module. Finally, AC500/NZ adsorbent considers a good candidate for water remediation. Monte Carlo (MC) simulation studies indicated the adsorption of MB molecule on the AC/NZ nanocomposite surface in dry system (no solvent) following a parallel mode in most of all studied configurations, confirming the strong interactions between the MB molecule and surfaces atoms of AC/NZ nanocomposite. The molecular structure analysis of MB molecule on the AC/NZ nanocomposite surface indicated that the adsorption process related to Van der Waals dispersion force. Consequently, this helps to trap MB molecule on the AC/NZ nanocomposite surface (i.e., physical adsorption), which supports our experimental results.