Reactive blue 19 adsorption onto Prunus dulcis shell–derived activated carbon: mechanistic insight, kinetic and thermodynamic evaluation

This study investigates the adsorption of Reactive Blue 19 (RB19) from aqueous solutions using KOH-activated carbon derived from Prunus dulcis shell waste. The adsorbent exhibited a highly microporous structure with a BET surface area of 1462.21 m2 g−1. Equilibrium analysis revealed heterogeneous multilayer adsorption behavior dominated by pore-filling mechanisms, while kinetic results showed that the pseudo-second-order model provided the best empirical description of the adsorption rate. Thermodynamic parameters (ΔH° = +8.11 kJ mol−1, ΔG° < 0) confirmed that the adsorption process is spontaneous, endothermic, and governed predominantly by physisorption. Compared with previously reported biomass-derived activated carbons, the prepared adsorbent exhibited competitive textural properties together with improved mechanistic interpretation of RB19 adsorption behavior. The study establishes a direct relationship between activation conditions, pore structure evolution, adsorption energetics, and temperature-dependent adsorption behavior. These findings demonstrate the potential of almond shell–derived activated carbon as a sustainable adsorption material for advanced wastewater treatment and provide mechanistic insight relevant to adsorption-based chemical engineering applications.