Enhanced mechanical properties and chromium (VI) immobilization via defect-tailored UiO-66-(OH)2 in cement-stabilized iron tailings

The utilization of cement-stabilized iron tailings as pavement base necessitates rigorous scrutiny of heavy metal ion leaching, particularly under fluctuating environmental pH conditions. Given the insufficient capacity of cement to stabilize Cr(Ⅵ), this paper explores the integration of defect-engineered metal-organic frameworks (MOFs) as additives in cement-stabilized iron tailings to reduce Cr(Ⅵ) leaching. Results shows that the utilization of MOFs material mitigates Cr(VI) leaching in cement-stabilized iron tailings while enhancing their mechanical properties. The Cr(Ⅵ) leaching from samples with the addition of UiO-66-(OH)₂ and UiO-66-(OH)₂-D exhibited a substantial reduction of 60.2 % and 88.6 %, respectively. The stabilized mechanism is attributed to the strong affinity between Cr(Ⅵ) and hydroxyl groups in MOFs. Furthermore, UiO-66-(OH) 2 -D has a larger pore diameter to expose more hydroxyl groups, which greatly improves its adsorption performance for Cr(Ⅵ). Meanwhile, the unconfined compressive strength (UCS), splitting strength and compressive resilience modulus increased by 13.4 %, 35.1 % and 45.7 %, respectively. The mechanisms underlie that the MOFs enhanced the early hydration process and optimized of the pore size distribution within the solidified body. This study presents a viable and efficient approach for the sustained mitigation of Cr(Ⅵ) leaching within cement-stabilized iron tailings.