Adsorption of methyl red on biogenic Ag@Fe nanocomposite adsorbent: Isotherms, kinetics and mechanisms

Abstract

UV–visible spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy were used for the characterization of core-shell Ag@Fe bimetallic nanocomposites. Thermal and photochemical methods were used for the degradation of methyl red in the presence of Ag@Fe. Batch experiments showed that the initial [dye], dose of Ag@Fe, [NaBH4], and temperature were affected by degradation and adsorption. The kinetics study showed that the removal had an induction period followed by an autoacceleration, which depended on the dose. The apparent pseudo-first order rate constants for the degradation of methyl red (MR) increased and decreased with increasing [Ag@Fe] and [NaBH4], respectively, but remained constant at higher [NaBH4]. The equilibrium adsorption data were fitted to Langmuir, Freundlich and Temkin isotherms. The maximum adsorption capacity from the Langmuir isotherm was determined to be 125 mg/g for the physisorption of MR onto the surface of Ag@Fe. The pseudo-first rate constant was calculated (7.5 × 10−3 s−1) for the UV-light assisted degradation of MR.