Sorption of metal ions from aqueous solution by sulfonated calix[4]arene intercalated with layered double hydroxide

Selective Removal of metal ions from simulated wastewater by sulfonated calix[4]arene intercalated with layered double hydroxide (SC4A-NO₃-LDH) is reported in the present paper. The SC4A-NO₃-LDH exhibited high adsorption performance towards metal ions with selectivity order of Fe(III) > Cu(II) > Pb(II) > Ag(I) for heavy metal ions, and Eu(III) > Nd(III) > La(III) for rare earth metal ions. Kinetics of Fe³⁺, Cu²⁺ and Eu³⁺ were found to follow pseudo-second-order reaction, suggesting chemisorption mechanism. Efficient sorption, with 100% removal rate and 3.80 × 10⁷ mL/g distribution coefficient (K_d) towards Fe(III) is typical potential of SC4A-NO₃-LDH. For Cu²⁺ and Eu³⁺ ions sorption, K_d values of 1.03 × 10⁶ and 7.25 × 10⁶ mL/g, and removal rates of 99.88 and 99.98%, respectively, were obtained. 0.005 g of SC4A-NO₃-LDH was enough to lower 2.6 ppm of Fe³⁺ -< 1 ppb. After the sorption, samples were characterized by analytical methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform Infrared spectroscopy (FTIR) and proved that the target ions on their respective samples. XRD and FTIR were also used to check the stability of the samples after sorption.