Remoção de cobre em álcool etílico hidratado combustível utilizando amêndoas de baru (Dypterix alata)

Abstract

In this study, a methodology was developed for removal of copper in hydrated ethanol fuel, using baru almonds (Dypterix alata). To investigate the adsorption capacity of baru almonds, studies were accomplished being varied the type of chemical treatment, strip sizes, time of contact, and pH of the solution, seeking the construction of adsorption isotherms and the determination of ideal conditions of the process, using as working solution the hydrated ethanol fuel sample acquired in a local fuel station. Different techniques were applied for the characterization of the material such as thermogravimetric analysis (TGA), superficial charge of the material (pHpcz), and Fourier-transformed infrared spectroscopy (FT-IR). TGA results indicated that almonds after acid treatment presented larger thermal degradation when compared with in natura almonds. The pHpcz of in natura and acid-treated almonds were 6.85 and 4.10, respectively. The confirmation of the functional groups of the acid-treated almonds by FT-IR suggests the presence of proteins, fatty acids, carbohydrates, and lipids. The largest capacity of copper removal was observed for the following conditions: treatment with 0.5 mol L-1 HNO3, granulometry range from 250 to 500 μm, 45 minutes as contact time, and pH solution at 7.0. Data of copper removal were adjusted to Langmuir and Freundlich models. The Langmuir parameters were qmax (mg g-1) of 5.80 and b (L mg-1) of 0.1013, and Freundlich parameters were Kf (L mg-1) of 0.753 and 1/n of 0.474. Tests for copper removal applied in commercial samples of hydrated ethanol fuel presented satisfactory results, with an average removal value of 92.60% for the initial concentration (spiked) of 25.00 mg L-1 of Cu(II) in the samples.