Silver nanoparticles deposition on silica, magnetite, and alumina surfaces for effective removal of Allura red from aqueous solutions

Silica, magnetite, and alumina surfaces were modified firstly by the coupling agent 3-Aminopropyltriethoxysilane. Silver nanoparticles were thus immobilized in the given functionalized surfaces via chemical reduction in aqueous solution using different reducing agents. The immobilized silver nanoparticles on the support surfaces were confirmed by the scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravemetric analysis. The efficiency of the synthesized nanocomposites for the removal of Allura red from aqueous solution has been assessed through some of experimental conditions. These include the type of support, type of reducing agent, initial dye concentration, adsorbent dose, temperature, and pH. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin isotherm models. The results followed the order: Langmuir > Temkin > Freundlich. Values of thermodynamic parameters (∆G^o, ∆H^o, and ∆S^o) of dye adsorption onto the surface of silica/silver nanoparticles, magnetite/silver nanoparticles, and alumina/silver nanoparticles were determined. They refer to the feasibility, spontaneity, and endothermic nature of dye adsorption on these surfaces. The adsorption process fitted well with pseudo-second-order kinetics and intraparticle diffusion model. This method can thus be considered applicable for the decontamination of wastewater from dyes.