Abstract Green almond hull was converted into three carbon based materials: raw hull (RGAH), pyrolyzed biochar (BGAH), and activated carbon (ACGAH) and comparatively examined for Pb 2+ removal from aqueous systems. Batch experiments identified optimal conditions at pH 5.51 and 120 min contact time with an initial metal concentration of 250 mg/L. At 298 K, equilibrium capacities reached 60.60 mg/g (RGAH), 163.93 mg/g (BGAH), and 526.31 mg/g (ACGAH), revealing a pronounced enhancement after thermal conversion and especially after chemical activation. Notably, the adsorption capacity of ACGAH was approximately 8.7 times higher than that of raw material and over 3 times greater than that of biochar, demonstrating a substantial performance improvement. The superior performance of ACGAH is associated with its highly developed porous framework and enriched surface chemistry, which intensify metal–surface interactions. These structural and morphological features were confirmed through characterization techniques including SEM, FTIR, and surface area analysis (BET), which collectively supported the relationship between material properties and adsorption performance. Adsorption behavior followed the pseudo‐second‐order kinetic model, indicating that Pb 2+ uptake is governed primarily by surface‐controlled chemical processes. Thermodynamic evaluation showed a spontaneous and endothermic character, supporting favorable interaction energetics. Furthermore, the exceptionally high adsorption capacity of 526.31 mg/g positions ACGAH among the more competitive adsorbents reported for Pb 2+ removal in the literature. The findings confirm that activation of green almond hull substantially upgrades its adsorption efficiency, highlighting ACGAH as a viable material for sustainable Pb 2+ remediation.
Altunkaynak et al. (Mon,) studied this question.