Removal of antimonate ions from aqueous solution using copper-aluminum layered double hydroxide

Copper-aluminum layered double hydroxide intercalated with NO^3- (NO₃·VCu-Al LDH) removed Sb(OH)_6- [Sb(V)] in solution. The removal of antimony (Sb) increased with increasing NO ₃Cu-Al LDH, regardless of reaction time. The pH increased from 4 to about 6, and then remained constant due to the buffering action of Cu ²⁺. The removal of Sb by NO³Cu-Al LDH occurred due to anion exchange between Sb(V) (i.e., Sb(OH)^6- in aqueous solution) and NO^3- in the interlayer of Cu-Al LDH. Some Sb(OH)_6- was likely adsorbed on the surface of NO₃·Cu-Al LDH. Conditions were difficult for intercalated OH^- to contribute to anion exchange with Sb(OH)_6-. The removal efficiency of Sb decreased as follows: NO³Cu-Al LDH >> Cl·Cu-Al LDH > CO^3-CuAl LDH > SO₄Cu-Al LDH, regardless of reaction time. C0 ₃Cu-Al LDH acted as an adsorbent for Sb(V) in aqueous solution. This reaction occurred around pH 6 when CO₃^2- in the interlayer of Cu-Al LDH reacted with H⁺ to produce HCO^3-. Therefore, HCO^3-in the interlayer of Cu-Al LDH was exchanged with Sb(V) in aqueous solution. Among four types of Cu-Al LDHs, NO³·Cu-Al LDH was superior for the treatment of Sb(V).