Preconcentration and determination of metal ions from fuel ethanol with a new 2,2′-dipyridylamine bonded silica

A silica surface chemically modified with [3-(2,2′-dipyridylamine) propyl] groups was prepared, characterized, and evaluated for its metal ion preconcentration in fuel ethanol. To our knowledge, we are the first authors who have reported the present modification on silica gel surface. The material was characterized using infrared spectra, scanning electronic microscopy, and 13C and 29Si solid-state NMR spectra. Batch and column experiments were conducted to investigate for metal ion removal from fuel ethanol. The results showed that the Langmuir model describes the sorption equilibrium data of the metal ions in a satisfactory way. From the Langmuir isotherms, the following maximum adsorption capacities (in mmol g−1) were determined: 1.81 for Fe(III), 1.75 for Cr(III), 1.30 for Cu(II), 1.25 for Co(II), 1.15 for Pb(II), 0.95 for Ni(II), and 0.87 for Zn(II). Thermodynamic functions, the change of free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) showed that the adsorption of metal ions onto Si–Pr–DPA was feasible, spontaneous, and endothermic. The sorption–desorption of the metal ions made possible the development of a preconcentration and quantification method of metal ions in fuel ethanol.

Figure optionsDownload high-quality image (53 K)Download as PowerPoint slideHighlights
► The synthesis of a new silica surface chemically modified (Si–Pr–DPA) was described.
► The new adsorbent showed to be an effective sorbent for metal ions in ethanol fuel.
► The new adsorbent presented a high large adsorption capacity.
► The adsorption process equilibrium condition is reached at time lower than 15 min.