Simultaneous Removal of Some Heavy Metal Ions From Aqueous Solutions by Magnetic Mg-Al Layered Double Hydroxide...

This work reports, the fabrication of a magnetic Mg-Al layered double hydroxide (LDH) nano-bio-composite functionalized with the microalga Dunaliella salina (D. salina) for enhanced heavy metal removal from aqueous systems. Unlike conventional LDH adsorbents or biomass-based biosorbents, this hybrid design leverages the high surface area and ion-exchange capacity of LDH together with the metal-binding microalgae, D. salina, yielding a synergistic enhancement in adsorption selectivity and capacity. In multi-cation systems, the nano-bio-composite exhibited superior uptake for Pb(II) and Cu(II), with thermodynamic analysis confirming endothermic (ΔH° > 0) and entropy-driven (ΔS° > 0) processes. Kinetic studies revealed that Cu(II), Cd(II), Ni(II), and Co(II) followed a pseudo-first-order mechanism, while Pb(II) conformed to a pseudo-second-order model. All adsorption data fitted the Langmuir model, indicating monolayer coverage. The material retained its performance for Pb(II) and Cu(II) over five regeneration cycles without significant efficiency loss. This novel microalga-LDH nano-bio-composite offers a sustainable, magnetically separable, and highly reusable adsorbent platform, addressing key limitations of current heavy metal remediation technologies.