Elimination of Safranin-O and a binary mixture of Safranin-O and methylene blue from water by adsorption on magnetite/Ag nanocomposite

Abstract

The present research aimed at the removal of Safranin-O (Saf-O) dye and a binary mixture of Saf-O and methylene blue (MB) from an aqueous solution by adsorption onto the surface of magnetite/Ag nanocomposite to find a feasible and an effective route for cleaning the wastewater from these dyes. The nanocomposite was synthesized by the co-precipitation method in the presence of nanosilver which in turn was prepared by the reduction of Ag⁺ by sodium citrate. The nanocomposite was characterized by FT-IR, XRD, SEM, EDX, and TEM techniques. The adsorption of the single Saf-O and its binary mixture with MB was studied under the effect of several experimental conditions. These conditions were the initial concentration of dyes, nanocomposite dose, Ag to magnetite ratio, pH of the medium, presence of salt, time of contact, and solution temperature. The adsorption process followed pseudo-second-order kinetics The Langmuir and Freundlich adsorption isotherms were applied and the data were best fitted with the Langmuir model confirming monolayer adsorption of dyes. The maximum adsorption capacity was 46.3 mg/g for the single Saf-O and (38.46 + 34.97) for the (Saf-O + MB) binary mixture at 30 °C. The adsorption process was spontaneous and endothermic. The recyclability of the magnetite/Ag nanocomposite was confirmed through five reusable cycles where it can be considered a promising adsorbent for wastewater treatment from dyes.