Direct synthesis of Al-HKUST-1 and its application as adsorbent for removal of congo red in water

Direct synthesis of Al-HKUST-1 was successfully carried out using the solvothermal method. The Al₂O₃ added into the reaction mixture was varied at 10, 20, 40, and 80% with respect to the weight of HKUST-1. The diffractogram patterns of the synthesized HKUST-1 and Al-HKUST-1 displayed characteristic peaks at 2θ of 6.5, 9.3, 11.4 and 13.3°, where all of these matched with that of the HKUST-1 standard. The FTIR spectra of the synthesized materials demonstrated an adsorption band at the same wavenumber as the reported HKUST-1. The surface morphology of the synthesized HKUST-1 had an octahedral form, whereas the synthesized Al-HKUST-1 had a random surface morphology. The N₂ adsorption–desorption isotherms showed that the specific surface areas of Al(10)-HKUST-1 and Al(40)-HKUST-1 were 512.6 dan 380.9 m²/g respectively, all of which were smaller than HKUST-1, which was 784.1 m²/g. The measurement results of the adsorption capacity of Al-HKUST-1 against congo red dye (CR) in water showed that Al(20)-HKUST-1 had the highest adsorption capacity of 315.15 mg/g, and followed the pseudo-second order kinetic and Langmuir isothermal adsorption.