Template-free synthesis of an eco-friendly flower-like Mg/Al/Fe-CLDH for efficient arsenate removal from aqueous solutions

Abstract

• A novel flower-like Mg/Al/Fe-CLDH was synthesized for As(V) removal. • Mg/Al/Fe-CLDH exhibited excellent acid and alkali resistance and reusability. • The maximum adsorption capacity of the Mg/Al/Fe-CLDH was 70.7 mg/g. • As(V) ions intercalated into the interlayer region to reconstruct the hydrotalcite. Mg/Al-LDH is widely used in the removal of aqueous pollutants due to the large surface and high anion exchange capacity, but the traditional Mg/Al-LDH for arsenic removal has a narrow range of pH application. The present study focused on the modifying of the lamellar Mg/Al-LDH to synthesize flower-like nanoparticles for arsenate removal in a wide pH range. Results showed that Mg/Al/Fe-CLDH (calcined Mg/Al/Fe-LDH) exhibited an extremely high arsenate removal efficiency (e.g., reducing As(V) from 10 mg/L to 1 µg/L) in a wide pH range (2–12). Furthermore, it can keep excellent removal efficiency for arsenate under a complex anions environment (co-existing with CO 3 2− , SO 4 2− , PO 4 3− , and F − ), and maintain 80% removal efficiency for arsenate after 4 regeneration cycles. SEM, XRD, and XPS results unveiled the following enhancing mechanism for arsenate removal by using this modified Mg/Al-LDH: 1) partial content of ferric ions were successfully insert into the layers of Mg/Al-LDH and substituted by aluminium ions, which produce more affiliative sites for arsenate and expand its feasibility in a wide pH ranges; 2) the flower-like structures facilitate to offer more adsorption sites for arsenate due to its larger specific surface area. In brief, this flower-like Mg/Al/Fe-CLDH has great application potential for eco-friendly purity of arsenate from complicated industrial wastewater.