Enhanced surface adsorption of Congo red dye by the metastable α-LiAlO2 over LiAl2(OH)7⋅2H2O

The current study addresses the comparison of the adsorption capacity of hydroxide intercalated lithium-aluminum-layered double hydroxide (Li–Al LDH) and the calcined layered double hydroxides (α-and γ-LiAiO2). The samples have been characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR). The surface area of the samples was measured by the BET method. The pH method determined the sample's point of zero charge (PZC), yielding values of 9.1 and 6.9 for α-LiAlO2 and Li–Al LDH. The metastable α-LiAlO2 adsorbed Congo red (CR) dye efficiently from aqueous solutions than the parent hydroxide intercalated Li–Al LDH and thermodynamically stableγ-LiAlO2. The α-LiAlO2 and Li–Al LDH exhibited adsorption capacities of 207 and 146 mg/g, respectively. The adsorption kinetics could be fitted well using the pseudo-second-order kinetics model. The adsorption mechanism has been proposed based on PXRD, FTIR spectra, zeta potential, and SEM measurements of CR dye adsorbed samples. The adsorption of CR dye by Li–Al LDH was favored by hydrogen bonding, whereas electrostatic interaction dominated whenα-LiAlO2 was used as an adsorbent.