Adsorptive Separation of Allura Red, Tartrazine, and Brilliant Blue Dyes from Aqueous Solution Using Amine-Modified SBA-15

Abstract

Food and textile dye effluents cause major health issues. organic dyes in industrial effluent are hazardous which can be purified by adsorption. But carbon recycling is difficult, thus recyclable adsorbents are advantageous. In this context, SBA-15/propyl-NH₂ was synthesized, characterized, and used to adsorb food dyes (brilliant blue, allura red, tartrazine) in water. The removal effectiveness (%) of adsorbent was examined considering pH, dose, concentration, time, and temperature. The mechanism of adsorption was examined using pseudo-first- and pseudo-second-order kinetics. Langmuir, Freundlich, and Temkin isotherms were used to evaluate adsorbent-adsorbate interactions. The thermodynamic parameters (∆G°, ∆S°, and ∆H°) were evaluated and compared. Langmuir adsorption isotherm showed monolayer adsorption for all dyes with R² values around 1. With rate constant (k₂) of 0.0003 to 0.0013 g/mg min, the kinetics followed pseudo-second-order model. The adsorption capacity of SBA-15/propyl-NH₂ for tartrazine, brilliant blue, allura red was estimated at 403.22 mg/g, 395.25 mg/g, 485.43 mg/g respectively. Adsorption occurs with a decrease in free energy, a negative enthalpy, and a decrease in entropy at 25 °C. The adsorbent recyclability was confirmed over three cycles, with no reduction in removal effectiveness (%). Therefore, the SBA-15/propyl-NH₂ nanocomposite effectively separates food and textile dyes from water-based solutions.