Mechanism of lithium adsorption by AlLi-LDH with Al–O octahedral ring

Abstract

Aluminum–lithium layered double hydroxide (AlLi-LDH) was synthesized using a co-precipitation method for Li⁺ adsorption. AlLi-LDH crystallized in space group of P32 or C2/m, where the microstructure had regular spherical shapes with diameters of 5–10 μm. The space group of AlLi-LDH only belonged to P32 after Li⁺ adsorption. The Li⁺ adsorption from a solution with a Li⁺ concentration of 95.4 mg/L reached 8.98 mg/g after 1 h. The adsorption amount increased to 16.50 mg/g after 48 h, where the Li⁺ adsorption capacity determined by applying the second-order adsorption model was 17.57 mg/g. The Mg²⁺/Li⁺ separation coefficient was 29536 when the mass ratio of Mg²⁺ to Li⁺ was 1067. The interaction strength of Li–O was weaker for AlLi-LDH in the P32, where the interaction occurs via the electrostatic effect. The Li⁺ adsorption and desorption occurred more readily in AlLi-LDH belonging to P32 space group.