Effective Synthesis and Adsorption Characteristics of KOH-Activated Carbon Derived from Biomass: Validation Methods, Kinetic and Thermodynamic Studies

In this study, active carbons with and without activator (KOH) were obtained from waste laurel nobilis fruit seeds. KOH-impregnated bay leaf seeds have been used as a low-cost, high-value adsorbent (KOH-AC) for the adsorption of crystal violet (CV) from aqueous solution. FTIR, TGA, BET and SEM were used to characterize KOH-AC. The surface area and average pore diameter of KOH-AC were determined to be 879.94 m2/g and 3.79 nm, respectively. The adsorption process was examined using two different kinds of kinetic models, known as pseudo-first order and pseudo-second order. The adsorption process followed the pseudo-second order kinetic model, according to the data for R2, ARE, Δqe (%), RMSE, SSE, SD, and MSE. The activation energy (Ea) was found to be 98.34 kJ/mol. The adsorption of CV on KOH-AC was found to be chemical adsorption. The additional activation parameters, including entropy (ΔS#,−253.4 J/mol K), enthalpy (ΔH#,−2.54 kJ/mol), and activation free energy (ΔG#, 72.97, 74.24, and 76.77 kJ/mol at 298, 303, 313 K, respectively), were determined using the Eyring equation. The equilibrium data collected were used in the Freundlich and the Langmuir adsorption isotherm models. The Langmuir isotherm model showed good fit to the equilibrium adsorption data. The adsorption equilibrium data of KOH-AC followed Langmuir isotherm model with the monolayer adsorption capacities of 138.89, 243.90 and 256.41, respectively. The thermodynamic values (ΔHo, ΔGo, and ΔSo) were likewise computed. ΔHo was calculated as 41.50 kJ/mol and ΔSo as 134 J/mol K.