A practical organometallic decorated nano-size SiO2–Al2O3 mixed-oxides for methyl orange removal from aqueous solution

•The ferrocene group decorated nano-organo SiO2–Al2O3 as a novel adsorbent.•The application of nano-adsorbent was studied to remove methyl orange.•It effectively removes 85% methyl orange from contaminated water under 25min.•The novel nano-adsorbent was very stable and easily separated from the purified water. In this study, the application of a functional ferrocene (ferrocenecarboxaldehyde) firmly heterogenized over a modified nano-size SiO2–Al2O3 mixed-oxides was reported as a novel adsorbent for the removal of methyl orange from aqueous solution. SiO2–Al2O3 mixed-oxides was functionalized with 3-aminopropyl-triethoxysilane (3-APTES) group and ferrocenecarboxaldehyde covalently linked on this organo-functionalized SiO2–Al2O3 mixed-oxides support. The synthesized materials were characterized by FT-IR spectroscopy, UV–vis, CHN elemental analysis, BET, TGA, ICP-MS, TEM, and XPS. The contact time to obtain equilibrium for maximum adsorption was 50min. XPS of Fe ions evidenced that most of the active sites of the nano-adsorbent is in the form of Fe3+ ions at the surface. The heterogeneous Fe3+ ions were found to be effective adsorbent for the removal of dyes from solution. The adsorption of methyl orange ions has been studied in terms of pseudo-first-order and pseudo-second-order kinetics, and the Freundlich, Langmuir, and Langmuir–Freundlich isotherm models have also been applied to the equilibrium adsorption data. The adsorption process was spontaneous and endothermic in nature and followed pseudo-second-order kinetic model.