Millimeter-sized Mg-Al-LDH nanoflake impregnated magnetic alginate beads (LDH-n-MABs): a novel bio-based sorbent for the removal of fluoride in water

Mg-Al-LDH nanoflake impregnated magnetic alginate beads (LDH-n-MABs) were successfully synthesized and their defluoridation performance was systematically evaluated. Batch experiments showed that the LDH-n-MABs outperformed many other reported adsorbents with higher adsorption capacities. The effects of various limiting factors including pH, contact time, initial fluoride concentration, temperature, and co-existing substances were investigated. XPS and FT-IR measurements evidenced the complex uptake mechanism of fluoride onto the LDH-n-MABs. The advantages of this adsorbent are as follows: (1) Mg-Al-LDH nanoflakes with a higher adsorption capacity for F- were immobilized into alginate beads without leaching, taking the safety issues concerning nanomaterials into consideration; (2) the prepared beads had a high magnetic sensitivity to an external magnetic field providing an easy and efficient way to separate them from aqueous solution; (3) the bio-based sorbents offer advantages such as biodegradability, hydrophilic properties, natural origin and a high abundance. Furthermore, the results from the real fluoride contaminated groundwater study confirmed the feasibility of LDH-n-MABs for fluoride removal.