Preparation of biomorphic Ni–Al LDHs using cotton from discarded T–shirt as a template and the adsorption capability for Congo red

Abstract

Biomorphic Ni–Al layered double-hydroxide (LDH) nanosheets with 3D hierarchical structures were synthesized with cotton from discarded T-shirt as templates. The as-prepared samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetry–differential thermal analysis, scanning electron microscopy, and energy-dispersive X-ray diffraction. Adsorption of Congo red (CR) by calcined Ni–Al layered double hydroxides (CLDH) from aqueous solution was investigated in detail. Different conditions were evaluated, including solution pH, amount of adsorbent, initial CR concentration, contact time, and temperature. The adsorption kinetics and equilibrium isotherms of the CLDH were studied by use of pseudo-first-order and pseudo-second-order kinetic models, and the Langmuir, Freundlich, and Dubinin–Radushkevich isotherms. Equilibrium isotherms of uptake of CR by CLDH were a good fit to the Freundlich equation, and the adsorption kinetics of CR followed a pseudo-second-order kinetic model. These results suggest that CLDH may be effective adsorbents for the removal of anionic dyes from wastewater.