Efficient removal of Congo Red Dye using a MgAl-LDH/cuttlebone composite adsorbent

In this work, a novel, eco-friendly composite material composed of MgAl-layered double hydroxide and cuttlebone (LDH/CB) was synthesized for the efficient adsorption of Congo Red dye from aqueous solutions. The LDH/CB composite was synthesized via a one-step co-precipitation method, and its crystallinity was confirmed by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The effects of key experimental parameters—including pH, contact time, and initial dye concentration—on the adsorption efficiency were systematically investigated. The adsorption kinetics followed the pseudo-first-order model, while the equilibrium data were well described by the Langmuir and D–R isotherm, with a maximum adsorption capacity of 380 mg/g. Thermodynamic analysis revealed that the adsorption process was spontaneous, exothermic, and primarily driven by electrostatic interactions. Moreover, the composite exhibited excellent reusability over five adsorption–desorption cycles, maintaining high stability in performance. These findings highlight the potential of the LDH/CB composite as an efficient and sustainable adsorbent for the treatment of dye-contaminated wastewater.