Removal of Acid Blue 25 from Aqueous Media by Magnetic-SBA-15/CPAA Super Adsorbent: Adsorption Isotherm, Kinetic, and Thermodynamic Studies

In this study, SBA-15 mesoporous silica was synthesized, magnetized, and then functionalized with cross-linked poly (acrylic acid) (CPAA) polymer, and the resulting adsorbent (Magnetic-SBA-15/CPAA) was used to remove Acid Blue 25 from aqueous media. X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer-Emmett-Teller method, and vibrating sample magnetometry were used in this study. The effective parameters on dye removal, including pH, contact time, temperature, and adsorbent dosage were investigated and optimized. The optimum condition was pH = 2, adsorbent dosage of 0.025 g, and contact time of 60 min at 25 degrees C. UV-vis spectrophotometer was used to determine the amount of residual dye in solution. To determine the type of adsorption isotherm, the Langmuir, Freundlich, Tempkin, and Dubinin-Radushkevich adsorption isotherm equations were used. Pseudo-first-order and pseudo-second-order models were used to determine the kinetics of adsorption and the results showed an appropriate fit for Langmuir adsorption isotherm (R-2 = 0.9901 and R-L = 0.0561) and the pseudo-second-order kinetics model (R-2 = 0.9944 and q(e,cal) = 236.68) with an adsorption capacity of 909.09 mg/g. Regarding the obtained values of thermodynamic parameters such as enthalpy (-30.287 kJ/mol) and Gibbs free energy, removal of Acid Blue 25 by Magnetic-SBA-15/CPAA was exothermic and spontaneous.