Efficient recovery of platinum and palladium by fixed‑bed column adsorption using acylthiourea‑ and amine‑modified silica

Abstract

The rising demand and limited natural reserves of platinum group metals (PGMs) have intensified the need for sustainable recovery from secondary sources. This study investigates the continuous fixed-bed column adsorption of platinum (Pt) and palladium (Pd) from aqueous solutions using silica-anchored acylthiourea and amine-modified adsorbents. Adsorption experiments were performed at pH 2 and a flow rate of 2.00 mL/min, with variations in bed height and metal concentration to optimise recovery. Among the four adsorbents tested, DTMSP-BT-SG exhibited the highest adsorption capacities, with Thomas model-derived values reaching 470.67 mg/g for Pt and 382.19 mg/g for Pd. Increasing bed height and metal concentration enhanced both breakthrough capacity and the volume of solution treated, with up to 4775 bed volumes processed. Comparison with batch-mode adsorption revealed that, although equilibrium was achieved more rapidly in batch systems, column mode enabled significantly higher treatment volumes and yielded higher capacities. Breakthrough data were best described by the Thomas and Yoon–Nelson models (R2 > 0.90), while the Bohart–Adams model was less predictive across the full breakthrough profile. The findings confirm the superior performance of acylthiourea-based adsorbents, particularly DTMSP-BT-SG, in large-scale continuous recovery of Pt and Pd from industrial and mining wastewater.