ADSORPTION OF DIRECT BLACK 22 FROM AQUEOUS SOLUTION USING Mg/Al LDH- ZEOLITE

Abstract

In this study, composite materials between Mg/Al Layered Double Hydroxide and natural zeolite (Mg/Al LDH-zeolite) were synthesized by co-precipitation method to remove Direct Black 22 (DB22) in aqueous solution. The characteristics of Mg/Al LDH-zeolite were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), Fourier transform infrared spectra (FTIR) and Brunauer–Emmett–Teller (BET) surface area. The adsorption process of Mg/Al LDH-zeolite for DB22 was evaluated through batch experiments to examine various parameters, including solution pH, contact time and initial DB22 concentration. The DB22 adsorption isotherm and kinetic data on Mg/AlLDH-zeolite were analyzed. The results show that DB22 could be removed well by using Mg/Al LDH-zeolite due to its large surface area (252.65 m²/g) and functional groups. The DB22 adsorption capacities of Mg/Al LDH-zeolite reached 27.45 mg/g, at an initial DB22 concentration of 150 mg/L, pH = 4, and contact time of 120 min. The adsorption isotherms of DB22 on Mg/Al LDH-zeolite were described well by Langmuir models with high R² values (R² > 0.95). The obtained data also well matched the pseudo-second-order models with R² values ≥ 0.97. Physisorption through electrostatic attraction and pore filling as the main adsorption mechanism.