Analysis of Breakthrough Curve Performance Using Theoretical and Empirical Models: Hg2+ Removal by Bone Char from Synthetic and Real Water

Bone char has been successfully prepared from ostrich bone waste (OBC) via the physical activation under the presents of N₂ gas and then was characterized by different techniques. The utility of the mass transport (MT) model to simulate the breakthrough curves of mercury(II) in a packed-bed adsorption column was evaluated and compared with the mathematical models (Bed Depth Service Time (BDST), Adams–Bohart (AB), Thomas, Dose–Response (DR), and Yoon–Nelson (YN)) under diverse operating factors such as influent concentration (35, 75, and 150 mg L⁻¹), inlet flow rate (5, 10, 15, and 20 mL min⁻¹), pH (2, 5, 7, and 9), and bed depth (10 and 20 cm). Based on the modeling results, it was concluded that the MT model had the best accuracy (R² = 99.31%, MRE = 0.745% and NRMSE = 6.15%), followed by Th, BDST, YN, DR, and AB. The sensitivity analysis showed that the simulated breakthrough curves were more sensitive to maximum adsorption capacity (q_T) than axial dispersion coefficient (D_L) and apparent equilibrium constant (k). All models overestimated the breakthrough curves (MRE > 0). OBC was able to eliminate the Hg(II) from the real samples (greywater and petrochemical wastewater), which indicated that the presence of organic compounds in wastewater had no effect on the mercury(II) adsorption efficiency. The overall results showed that the dissolution–precipitation process and ion-exchange reaction were involved in the adsorption of the mercury(II) by OBC.