Modified Layered Double Hydroxide Mg/M3+ (M3+ = Al and Cr) Using Metal Oxide (Cu) as Adsorbent for Methyl Orange and Methyl Red Dyes

Mg/Cr-layered double hydroxide (Mg/Cr-LDH) and Mg/Al-layered double hydroxide (Mg/Al-LDH) intercalated metal oxide (Mg/Cr-Cu and Mg/Al-Cu) were synthesized by the co-precipitation method which is indicated by the X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Brunauer Emmett Teller (BET) analysis. Mg/Cr-LDH intercalated metal oxide increased its surface area from 21.5 to 38.9 m2/g, while the surface area of Mg/Al-LDH from 23.2 to 30.5 m2/g. The adsorption capacity of Mg/Cr-Cu is 64.156 mg/g for methyl orange (MO) and 78.740 mg/g for methyl red (MR), and the adsorption capacity of Mg/Al-Cu is 97.087 mg/g for MO and 108.696 mg/g for MR. Equilibrium time on the adsorption process occurred at 90 minutes with adsorption kinetics followed by pseudo-second-order (PSO). The adsorption isotherm followed the Langmuir isotherm equation. Data of thermodynamic parameters indicate that the adsorption process in this study occurs spontaneously and endothermically. The regeneration results show that Mg/Cr-Cu and Mg/Al-Cu can be used for the 5 cycles regeneration process of MO and MR adsorption process. Interactions that occur between adsorbents and adsorbate include physical interactions, interactions with the involvement of hydrogen bonds, and electrostatic interactions.