Equilibrium and Thermodynamic Studies for the Removal of Eriochrome Black T dye from its Aqueous Solutions using Nano Carbon Prepared from Morus Nigra (Mulberry) Stem through two Stages of Carbonization

In this study, nano-scale activated carbon (NSAC) was synthesized using Morus Nigra (Mulberry) Stem as the precursor material. The carbonization process involved the utilization of KOH, followed by treatment with sodium hydroxide (NSAC-NaOH) to enhance micro-porosity, resulting in higher micro-porous activated carbon. A comprehensive characterization of the material was conducted using various analytical techniques, including Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) analysis, field emission scanning electron microscope (FE-SEM), Energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Demonstrated the presence of nano-scale particle size and exceptional porosity. Furthermore, the physical properties of the activated carbon were evaluated, encompassing parameters such as density, humidity, ash content, iodine number, methylene blue pH, and point of zero charge (pHPZC). Adsorption experiments were performed under optimized conditions, with a concentration of Eriochrome Black T (EBT) dye at (100  mg/L), and an adsorbent dose of (0.4g/L , initial concentration(60-110 mg/L), highlighting acidic solutions with a pH of (3.0) as exhibiting superior dye removal capacity, but considering economic factors, the natural pH (5.2) level was determined to be optimal for subsequent experiments, facilitating interaction with EBT dye molecules via electrostatic attraction. Thermodynamic analysis of the adsorption process, conducted within a temperature range of (25–65 ºC), indicated an endothermic nature (+∆Ho), signifying physical adsorption (∆Ho < 40 kJ/mol). The negative free energy (-∆Go) suggested the spontaneity of the process, while the positive entropy value (+∆So) indicated disorder. Additionally, the Langmuir isotherm model was found to appropriately describe the adsorption behavior of the EBT dye.