Phosphate Removal by ZIF‐8 and Magnetic Fe ₃ O ₄ /ZIF‐8: A Comparative Study of Capacity, Kinetics, and Regeneration

ABSTRACT This study presents a comparative evaluation of phosphate adsorption on pristine ZIF‐8 and Fe 3 O 4 ‐doped ZIF‐8 (Fe 3 O 4 /ZIF‐8), a hybrid adsorbent combining high surface area with magnetic separability. Structural integrity and composition were confirmed using SEM, XRD, FTIR, and XPS. Comparative studies on phosphate removal by Fe 3 O 4 /ZIF‐8 are scarce, and this work provides a direct evaluation against pristine ZIF‐8 under identical conditions. ZIF‐8 exhibited a higher maximum adsorption capacity (521 mg/g equivalent to 170 mg P/g at 50°C) but slower adsorption rates ( k 1 = 0.0852–0.1303 min −1 ). In contrast, Fe 3 O 4 /ZIF‐8 showed a lower capacity (187 mg/g, 61 mg P/g, at 50°C) but faster kinetics ( k 1 = 0.1513–0.2533 min −1 ), along with improved selectivity in the presence of competing anions, and superior reusability, retaining ~60% efficiency after 4 cycles versus ~33% for ZIF‐8. Adsorption followed the pseudo‐second‐order and Sips models, and both materials were effective at acidic to neutral pH. These findings demonstrate that Fe 3 O 4 incorporation does not necessarily increase adsorption capacity but provides operational advantages such as magnetic retrievability, faster adsorption, and greater regeneration stability. The comparative perspective offers valuable insight into the rational design of multifunctional MOF‐based adsorbents, positioning Fe 3 O 4 /ZIF‐8 as a promising candidate for sustainable phosphate removal in complex water environments.